Musculoskeletal Oncology — MCQs

Q: Which of the following are features of Gorham's disease (Disappearing Bones)?

All of the above. **Gorham’s Disease**, also known as **Vanishing Bone Disease** or Phantom Bone Disease, is a rare musculoskeletal condition characterized by the spontaneous, progressive destruction and resorption of bone tissue. ### **Explanation of Options** * **Option A:** The hallmark of Gorham’s disease is the proliferation of thin-walled vascular or lymphatic channels within the bone. This leads to **progressive osteolysis** (bone disappearance) associated with **hemangiomatosis** or **lymphangiectasis**. The bone is replaced by fibrous connective tissue. * **Option B:** The disease typically spreads across joints to involve **contiguous bones** (e.g., spreading from the humerus to the scapula or from one vertebra to the next). While localized, it can occasionally manifest in multiple non-contiguous anatomical sites. * **Option C:** The clinical presentation is often insidious. Patients may experience **dull aching pain**, localized swelling, or a **pathological fracture** following minor trauma. In severe cases involving the ribs or spine, it can lead to chylothorax. Since all statements accurately describe the pathophysiology, progression, and clinical presentation of the disease, **Option D (All of the above)** is the correct answer. ### **High-Yield Clinical Pearls for NEET-PG** * **Radiology:** Characterized by "tapering" of the ends of remaining bone (sucker-stick appearance) and eventual complete disappearance of the bone shadow. * **Key Feature:** Unlike most bone tumors, Gorham’s disease **crosses joint spaces** to involve adjacent bones. * **Biopsy:** Shows non-malignant proliferation of thin-walled vessels; there is a notable **absence of osteoclasts** (the resorption is mediated by the vascular tissue). * **Complication:** **Chylothorax** is a life-threatening complication if the disease involves the thoracic cage.

Q: Onion peel appearance on radiograph is not seen in which of the following conditions?

Fibrous dysplasia. **Explanation:** The "onion peel" appearance (lamellated periosteal reaction) is a radiographic sign caused by the rhythmic or episodic lifting of the periosteum, leading to the deposition of multiple concentric layers of new bone. **1. Why Fibrous Dysplasia is the Correct Answer:** Fibrous dysplasia is a benign fibro-osseous lesion where normal bone is replaced by fibrous tissue and immature trabeculae. It is an **intramedullary** process that does not typically involve the periosteum. Therefore, it does not produce a periosteal reaction. Its classic radiographic appearance is described as **"Ground-glass opacification"** with a well-defined "rind" of sclerotic bone. **2. Analysis of Incorrect Options:** * **Ewing’s Sarcoma:** This is the classic association for onion peel appearance. The aggressive nature of this tumor causes rapid, successive layers of periosteal bone formation. * **Garre’s Osteomyelitis:** Also known as Chronic Sclerosing Osteomyelitis with proliferative periostitis. It is a low-grade chronic infection (often in the mandible) that stimulates the periosteum to form reactive peripheral bone in a lamellated pattern. * **Osteogenic Sarcoma (Osteosarcoma):** While "Sunburst" and "Codman’s triangle" are more common, Osteosarcoma is a highly aggressive tumor that can occasionally present with a lamellated (onion peel) appearance depending on the rate of tumor growth. **Clinical Pearls for NEET-PG:** * **Onion Peel Appearance:** Seen in Ewing’s sarcoma, Garre’s osteomyelitis, Osteosarcoma, and sometimes Langerhans Cell Histiocytosis (LCH). * **Ground Glass Appearance:** Pathognomonic for Fibrous Dysplasia. * **Sunburst/Sunray Appearance:** Highly suggestive of Osteosarcoma. * **Codman’s Triangle:** Indicates an aggressive process (malignancy or subperiosteal abscess) lifting the periosteum rapidly.

Q: Chemotherapy of Ewing's sarcoma includes all except?

5-Fluorouracil. **Explanation:** Ewing’s Sarcoma is a highly malignant, small round blue cell tumor that is exquisitely sensitive to chemotherapy. The standard of care involves a multimodal approach (Chemotherapy + Surgery/Radiotherapy). **Why 5-Fluorouracil (5-FU) is the correct answer:** 5-Fluorouracil is an antimetabolite primarily used in the treatment of epithelial malignancies (GI tract, breast, and head/neck cancers). It has **no established role** in the management of Ewing’s Sarcoma. **Analysis of other options (The VAC-IE Regimen):** The current standard chemotherapy for Ewing's Sarcoma follows the **VAC-IE** protocol, which includes: * **Vincristine** * **Actinomycin D (Dactinomycin):** An antitumor antibiotic that inhibits RNA synthesis (Option B). * **Cyclophosphamide** * **Ifosfamide** * **Etoposide** * **Doxorubicin (Adriamycin):** An anthracycline that is a cornerstone in treating both Ewing’s and Osteosarcoma (Option A). * **Topotecan:** A Topoisomerase I inhibitor often used in second-line or salvage therapy for recurrent/refractory Ewing’s Sarcoma (Option C). **High-Yield Clinical Pearls for NEET-PG:** * **Genetics:** Characterized by the **t(11;22)** translocation, leading to the **EWS-FLI1** fusion gene. * **Radiology:** Classic **"Onion-peel"** periosteal reaction. * **Histology:** Small round blue cells that are **PAS positive** (due to cytoplasmic glycogen) and express **CD99 (MIC-2).** * **Site:** Most common in the diaphysis of long bones (Femur is most common). * **Prognosis:** The most important prognostic factor is the presence of metastasis at the time of diagnosis (Lungs and Bone marrow are common sites).

Q: Codman's triangle is seen in which of the following conditions?

Osteosarcoma. ### Explanation **Codman’s Triangle** is a classic radiological sign representing an aggressive **periosteal reaction**. It occurs when a rapidly growing lesion (usually a tumor) lifts the periosteum away from the bone, leaving a triangular area of new subperiosteal bone at the margin where the periosteum is still attached. #### Why Osteosarcoma is Correct: **Osteosarcoma** is the most common primary malignant bone tumor in adolescents. Because it is highly aggressive and grows rapidly, it frequently breaches the cortex and elevates the periosteum. This results in characteristic periosteal reactions: **Codman’s Triangle** and the **Sunburst (Spiculated) appearance**. #### Why Other Options are Incorrect: * **Chondroblastoma:** A benign, epiphyseal tumor typically seen in young patients. It usually presents as a well-defined lytic lesion with a "fluffy" or "popcorn" calcification, but lacks aggressive periosteal reactions. * **Chondrosarcoma:** While malignant, it often presents in older adults with "endosteal scalloping" and "ring-and-arc" calcifications. While it can show periosteal changes, it is less classically associated with Codman’s Triangle than Osteosarcoma. * **Giant Cell Tumor (GCT):** A "benign but locally aggressive" tumor located in the epiphysis (extending to the subchondral bone). It typically shows a **"Soap-bubble appearance"** and lacks a periosteal reaction because it expands the bone rather than lifting the periosteum abruptly. #### NEET-PG High-Yield Pearls: * **Codman’s Triangle** is not pathognomonic for Osteosarcoma; it can also be seen in **Ewing’s Sarcoma**, subacute osteomyelitis, and active hematomas. * **Ewing’s Sarcoma** is more classically associated with an **"Onion-skin"** (lamellated) periosteal reaction. * **Osteosarcoma** most commonly occurs around the knee (distal femur/proximal tibia) and is associated with a rise in **Serum Alkaline Phosphatase**.

Q: A child 10 yrs of age presents with a mass on his left thigh. The mass seems to be arising from the diaphysis of the femur and involving the soft tissue of the thigh. The child is having fever also. Give your most probable diagnosis -

Ewing's sarcoma. ***Ewing's sarcoma*** - **Ewing's sarcoma** commonly presents in children and adolescents, often involving the **diaphysis of long bones** like the femur. - The presence of a **soft tissue mass** and **fever** are characteristic systemic symptoms due to its aggressive nature and rapid growth. *Osteosarcoma* - While it is a common pediatric bone tumor, **osteosarcoma** typically arises in the **metaphysis** of long bones, not the diaphysis. - Systemic symptoms like fever are less common at presentation compared to Ewing's sarcoma unless there's significant metastatic disease. *Chondrosarcoma* - **Chondrosarcoma** is a malignant tumor of cartilage that usually affects older adults and rarely occurs in children. - It typically affects the **pelvis, shoulder, or long bones**, but a fever and involvement of the soft tissue with a diaphyseal origin are less classic presentation. *Malignant fibrous histiocytoma* - **Malignant fibrous histiocytoma** (now often termed undifferentiated pleomorphic sarcoma) is a tumor of adulthood, primarily affecting individuals over 40 years of age. - While it can involve deep soft tissues and bone, it is an extremely rare diagnosis in a 10-year-old child.

Q: A 20-year old male patient presents with pain on movement. X-ray of knee joint shows lytic lesion on the upper end of tibia. What is the likely diagnosis?

Osteoclastoma. **Osteoclastoma** - An **osteoclastoma**, also known as a **giant cell tumor of bone**, typically presents in young adults (20-40 years old) and is characterized by a **lytic lesion** often located in the **epiphysis or metaphysis** of long bones, particularly around the knee joint (distal femur or proximal tibia). - These tumors are locally aggressive and can cause pain and swelling. *Simple bone cyst* - A **simple bone cyst (unicameral bone cyst)** is usually found in younger individuals (under 20) and is a **fluid-filled lesion** that often appears as a **central, expansile lytic lesion** in the **metaphysis** of long bones, commonly the proximal humerus or femur, not typically the epiphysis. - These are often painless and discovered incidentally or due to a pathological fracture. *Multiple myeloma* - **Multiple myeloma** is a plasma cell malignancy primarily affecting older adults (typically >50 years old) and presents with **multiple "punched-out" lytic lesions** in various bones (skull, spine, ribs, pelvis), rather than a solitary lytic lesion in a young adult. - It is associated with systemic symptoms such as anemia, hypercalcemia, renal failure, and abnormal immunoglobulins. *Adamantinoma* - An **adamantinoma** is a rare, malignant bone tumor that almost exclusively occurs in the **tibia**, but it typically presents as a **lytic, often eccentric lesion with sclerotic margins** and occasionally a "soap bubble" appearance, and while it occurs in young adults, it is a very rare diagnosis compared to osteoclastoma for a knee lytic lesion. - It often has a characteristic histological appearance resembling epithelial tissue.

Q: A young girl presented with swelling of right thigh, with history of trauma 2 months back. Now she presents with swelling at mid-shaft of femur & low grade fever. ESR is mildly raised. X-ray shows a laminated periosteal reaction. Next line of investigation would be:

MRI. ***MRI*** - An **MRI** is the most appropriate next step as it provides excellent detailed imaging of soft tissues and bone marrow, allowing better characterization of the **periosteal reaction**, identifying abscesses, and assessing the extent of bone involvement, crucial for differentiating between infection and tumor. - The presence of a **laminated periosteal reaction** (like an "onion peel") on X-ray, in conjunction with localized swelling and low-grade fever, is highly suggestive of subacute osteomyelitis or even some bone tumors like Ewing sarcoma, for which MRI is superior for defining the extent. *Bone scan* - A **bone scan** (technetium-99m) is sensitive for detecting increased bone turnover, which occurs in infections and tumors, but it is **non-specific**, meaning it cannot differentiate between these conditions. - While it could show increased uptake in the affected area, it would not provide the anatomical detail needed to characterize the lesion or guide further management as effectively as an MRI. *Blood count & CRP* - A **blood count and CRP** would provide information on systemic inflammation (e.g., leukocytosis, elevated CRP for infection), but these are **non-specific**. - While ESR is already mildly raised, these blood tests would confirm generalized inflammation but **cannot localize or characterize the lesion** in the bone, offering little diagnostic value for the specific problem at this stage without imaging. *Biopsy* - A **biopsy** is an invasive procedure and is typically performed after initial imaging studies like X-ray and MRI have characterized the lesion to guide the biopsy site and help determine the nature of the condition (e.g., infection vs. tumor). - Performing a biopsy as the immediate next step without detailed imaging to assess the extent and nature of the lesion would be premature and potentially less effective in diagnosis.

Q: An 8 yr old child is having fever with pain and swelling in mid thigh. On Xray lamellated appearance and Codman's triangle is present. Histopathologic examination shows small round cells positive for MIC-2. What is the most likely diagnosis?

Ewings sarcoma. ***Ewings sarcoma*** - The combination of **fever with pain and swelling** in a child, **lamellated (onion-skin) periosteal reaction**, **Codman's triangle** on X-ray, and **small round cells positive for MIC-2 (CD99)** on histopathology is classic for Ewing's sarcoma. - This highly aggressive bone tumor primarily affects children and young adults, often presenting with systemic symptoms and a diaphyseal or metadiaphyseal location in long bones. *Chondrosarcoma* - This tumor is characterized by the production of **cartilage matrix** and typically affects older adults (40-70 years old), not children. - Radiographically, it often shows **calcifications with rings and arcs** within a lucent lesion, and histopathology reveals chondrocytes, not small round cells positive for MIC-2. *Chondroblastoma* - Chondroblastoma is a rare, **benign cartilage tumor** that typically occurs in the **epiphysis of long bones** in adolescents and young adults. - It usually presents as a well-defined lytic lesion and does not typically show lamellated periosteal reactions or positive MIC-2 staining, nor does it commonly present with fever. *Osteosarcoma* - While osteosarcoma is also an aggressive bone tumor affecting children and adolescents, it is characterized by the production of **osteoid (immature bone)**. - Radiographically, it often presents with a **"sunburst" pattern** due to spiculated periosteal reaction and a **Codman's triangle**, but histopathology shows malignant osteoblasts, not small round cells positive for MIC-2.

Q: A patient with metastatic breast cancer presents with pathological fracture of femur. What is the best fixation method?

Long Intramedullary Nail. ***Long Intramedullary Nail*** - Provides **strong internal fixation** that can bear weight immediately, crucial for patients with a limited life expectancy due to metastatic disease. - Stabilizes the entire bone, preventing further **pathological fractures** in the diaphysis and allowing earlier mobilization and pain relief. *External Fixator* - Primarily used for **temporary stabilization** in severe open fractures or polytrauma, and not for definitive fixation of pathological fractures. - High risk of **pin tract infections** and patient discomfort, making it unsuitable for long-term management in cancer patients. *Dynamic Hip Screw* - Primarily used for **intertrochanteric hip fractures**, which are typically proximal femur fractures. - Less effective for **diaphyseal fractures** or for stabilizing bone weakened by metastatic disease along its entire length. *Plate and Screws* - While effective for some fractures, plates may not provide sufficient **load-bearing capacity** for extensively lytic or weakened bone in metastatic disease without extensive bone grafting. - Risk of **stress shielding** and subsequent re-fracture proximal or distal to the plate, especially when the intramedullary canal is compromised by tumor.

Q: Elderly female present with pain and swelling in the thigh. Xray shows multiple lytic lesions in distal femur with no periosteal reaction. Aspirate from the swelling shows homogenous serosanguinous fluid with RBCs. Which investigation can confirm the diagnosis?

Biopsy. ***Biopsy*** - A biopsy is the **definitive diagnostic tool** for establishing the presence of malignant cells that would cause lytic lesions and serosanguinous fluid in an elderly patient. - The findings of **multiple lytic lesions** in an elderly patient, coupled with serosanguinous fluid, strongly suggest a primary bone tumor or metastatic disease, which can only be confirmed histologically. *S. PTH levels* - **Elevated PTH** levels are indicative of **hyperparathyroidism**, which can cause bone resorption and lytic lesions (osteitis fibrosa cystica). - However, in this case, the fluid aspirate points towards a more localized, possibly neoplastic process rather than a systemic metabolic bone disorder as the primary concern. *S. Calcium levels* - **Hypercalcemia** can be associated with lytic bone lesions, particularly in cases of malignancy (e.g., **multiple myeloma** or **metastatic cancer**). - While supportive, calcium levels alone are insufficient to **confirm the specific diagnosis** of the underlying cause of the lytic lesions. *CD1a IHC* - **CD1a immunohistochemistry** is primarily used to diagnose **Langerhans cell histiocytosis**, a condition typically seen in children and young adults. - Given the patient's age and the imaging findings of multiple lytic lesions, Langerhans cell histiocytosis is an unlikely diagnosis, making CD1a IHC not the primary or confirming investigation.

Musculoskeletal Oncology Indian Medical PG Practice Questions and MCQs

Question 1: Which of the following are features of Gorham's disease (Disappearing Bones)?

A. Progressive disappearance of bone associated with multiple hemangiomatosis or multiple lymphangiectasis
B. Usually the progression involves contiguous bones, but occasionally multiple sites are affected
C. Patients present with mild pain or with pathological fracture
D. All of the above (Correct Answer)

Explanation: **Gorham’s Disease**, also known as **Vanishing Bone Disease** or Phantom Bone Disease, is a rare musculoskeletal condition characterized by the spontaneous, progressive destruction and resorption of bone tissue. ### **Explanation of Options** * **Option A:** The hallmark of Gorham’s disease is the proliferation of thin-walled vascular or lymphatic channels within the bone. This leads to **progressive osteolysis** (bone disappearance) associated with **hemangiomatosis** or **lymphangiectasis**. The bone is replaced by fibrous connective tissue. * **Option B:** The disease typically spreads across joints to involve **contiguous bones** (e.g., spreading from the humerus to the scapula or from one vertebra to the next). While localized, it can occasionally manifest in multiple non-contiguous anatomical sites. * **Option C:** The clinical presentation is often insidious. Patients may experience **dull aching pain**, localized swelling, or a **pathological fracture** following minor trauma. In severe cases involving the ribs or spine, it can lead to chylothorax. Since all statements accurately describe the pathophysiology, progression, and clinical presentation of the disease, **Option D (All of the above)** is the correct answer. ### **High-Yield Clinical Pearls for NEET-PG** * **Radiology:** Characterized by "tapering" of the ends of remaining bone (sucker-stick appearance) and eventual complete disappearance of the bone shadow. * **Key Feature:** Unlike most bone tumors, Gorham’s disease **crosses joint spaces** to involve adjacent bones. * **Biopsy:** Shows non-malignant proliferation of thin-walled vessels; there is a notable **absence of osteoclasts** (the resorption is mediated by the vascular tissue). * **Complication:** **Chylothorax** is a life-threatening complication if the disease involves the thoracic cage.

Question 2: Onion peel appearance on radiograph is not seen in which of the following conditions?

A. Garre's osteomyelitis
B. Ewing's sarcoma
C. Osteogenic sarcoma
D. Fibrous dysplasia (Correct Answer)

Explanation: **Explanation:** The "onion peel" appearance (lamellated periosteal reaction) is a radiographic sign caused by the rhythmic or episodic lifting of the periosteum, leading to the deposition of multiple concentric layers of new bone. **1. Why Fibrous Dysplasia is the Correct Answer:** Fibrous dysplasia is a benign fibro-osseous lesion where normal bone is replaced by fibrous tissue and immature trabeculae. It is an **intramedullary** process that does not typically involve the periosteum. Therefore, it does not produce a periosteal reaction. Its classic radiographic appearance is described as **"Ground-glass opacification"** with a well-defined "rind" of sclerotic bone. **2. Analysis of Incorrect Options:** * **Ewing’s Sarcoma:** This is the classic association for onion peel appearance. The aggressive nature of this tumor causes rapid, successive layers of periosteal bone formation. * **Garre’s Osteomyelitis:** Also known as Chronic Sclerosing Osteomyelitis with proliferative periostitis. It is a low-grade chronic infection (often in the mandible) that stimulates the periosteum to form reactive peripheral bone in a lamellated pattern. * **Osteogenic Sarcoma (Osteosarcoma):** While "Sunburst" and "Codman’s triangle" are more common, Osteosarcoma is a highly aggressive tumor that can occasionally present with a lamellated (onion peel) appearance depending on the rate of tumor growth. **Clinical Pearls for NEET-PG:** * **Onion Peel Appearance:** Seen in Ewing’s sarcoma, Garre’s osteomyelitis, Osteosarcoma, and sometimes Langerhans Cell Histiocytosis (LCH). * **Ground Glass Appearance:** Pathognomonic for Fibrous Dysplasia. * **Sunburst/Sunray Appearance:** Highly suggestive of Osteosarcoma. * **Codman’s Triangle:** Indicates an aggressive process (malignancy or subperiosteal abscess) lifting the periosteum rapidly.

Question 3: Chemotherapy of Ewing's sarcoma includes all except?

A. Doxorubicin
B. Dactinomycin
C. Topotecan
D. 5-Fluorouracil (Correct Answer)

Explanation: **Explanation:** Ewing’s Sarcoma is a highly malignant, small round blue cell tumor that is exquisitely sensitive to chemotherapy. The standard of care involves a multimodal approach (Chemotherapy + Surgery/Radiotherapy). **Why 5-Fluorouracil (5-FU) is the correct answer:** 5-Fluorouracil is an antimetabolite primarily used in the treatment of epithelial malignancies (GI tract, breast, and head/neck cancers). It has **no established role** in the management of Ewing’s Sarcoma. **Analysis of other options (The VAC-IE Regimen):** The current standard chemotherapy for Ewing's Sarcoma follows the **VAC-IE** protocol, which includes: * **Vincristine** * **Actinomycin D (Dactinomycin):** An antitumor antibiotic that inhibits RNA synthesis (Option B). * **Cyclophosphamide** * **Ifosfamide** * **Etoposide** * **Doxorubicin (Adriamycin):** An anthracycline that is a cornerstone in treating both Ewing’s and Osteosarcoma (Option A). * **Topotecan:** A Topoisomerase I inhibitor often used in second-line or salvage therapy for recurrent/refractory Ewing’s Sarcoma (Option C). **High-Yield Clinical Pearls for NEET-PG:** * **Genetics:** Characterized by the **t(11;22)** translocation, leading to the **EWS-FLI1** fusion gene. * **Radiology:** Classic **"Onion-peel"** periosteal reaction. * **Histology:** Small round blue cells that are **PAS positive** (due to cytoplasmic glycogen) and express **CD99 (MIC-2).** * **Site:** Most common in the diaphysis of long bones (Femur is most common). * **Prognosis:** The most important prognostic factor is the presence of metastasis at the time of diagnosis (Lungs and Bone marrow are common sites).

Question 4: Codman's triangle is seen in which of the following conditions?

A. Chondroblastoma
B. Osteosarcoma (Correct Answer)
C. Chondrosarcoma
D. Giant Cell Tumor

Explanation: ### Explanation **Codman’s Triangle** is a classic radiological sign representing an aggressive **periosteal reaction**. It occurs when a rapidly growing lesion (usually a tumor) lifts the periosteum away from the bone, leaving a triangular area of new subperiosteal bone at the margin where the periosteum is still attached. #### Why Osteosarcoma is Correct: **Osteosarcoma** is the most common primary malignant bone tumor in adolescents. Because it is highly aggressive and grows rapidly, it frequently breaches the cortex and elevates the periosteum. This results in characteristic periosteal reactions: **Codman’s Triangle** and the **Sunburst (Spiculated) appearance**. #### Why Other Options are Incorrect: * **Chondroblastoma:** A benign, epiphyseal tumor typically seen in young patients. It usually presents as a well-defined lytic lesion with a "fluffy" or "popcorn" calcification, but lacks aggressive periosteal reactions. * **Chondrosarcoma:** While malignant, it often presents in older adults with "endosteal scalloping" and "ring-and-arc" calcifications. While it can show periosteal changes, it is less classically associated with Codman’s Triangle than Osteosarcoma. * **Giant Cell Tumor (GCT):** A "benign but locally aggressive" tumor located in the epiphysis (extending to the subchondral bone). It typically shows a **"Soap-bubble appearance"** and lacks a periosteal reaction because it expands the bone rather than lifting the periosteum abruptly. #### NEET-PG High-Yield Pearls: * **Codman’s Triangle** is not pathognomonic for Osteosarcoma; it can also be seen in **Ewing’s Sarcoma**, subacute osteomyelitis, and active hematomas. * **Ewing’s Sarcoma** is more classically associated with an **"Onion-skin"** (lamellated) periosteal reaction. * **Osteosarcoma** most commonly occurs around the knee (distal femur/proximal tibia) and is associated with a rise in **Serum Alkaline Phosphatase**.

Question 5: A child 10 yrs of age presents with a mass on his left thigh. The mass seems to be arising from the diaphysis of the femur and involving the soft tissue of the thigh. The child is having fever also. Give your most probable diagnosis -

A. Osteosarcoma
B. Chondrosarcoma
C. Ewing's sarcoma (Correct Answer)
D. Malignant fibrous histiocytoma

Explanation: ***Ewing's sarcoma*** - **Ewing's sarcoma** commonly presents in children and adolescents, often involving the **diaphysis of long bones** like the femur. - The presence of a **soft tissue mass** and **fever** are characteristic systemic symptoms due to its aggressive nature and rapid growth. *Osteosarcoma* - While it is a common pediatric bone tumor, **osteosarcoma** typically arises in the **metaphysis** of long bones, not the diaphysis. - Systemic symptoms like fever are less common at presentation compared to Ewing's sarcoma unless there's significant metastatic disease. *Chondrosarcoma* - **Chondrosarcoma** is a malignant tumor of cartilage that usually affects older adults and rarely occurs in children. - It typically affects the **pelvis, shoulder, or long bones**, but a fever and involvement of the soft tissue with a diaphyseal origin are less classic presentation. *Malignant fibrous histiocytoma* - **Malignant fibrous histiocytoma** (now often termed undifferentiated pleomorphic sarcoma) is a tumor of adulthood, primarily affecting individuals over 40 years of age. - While it can involve deep soft tissues and bone, it is an extremely rare diagnosis in a 10-year-old child.

Question 6: A 20-year old male patient presents with pain on movement. X-ray of knee joint shows lytic lesion on the upper end of tibia. What is the likely diagnosis?

A. Simple bone cyst
B. Osteoclastoma (Correct Answer)
C. Multiple myeloma
D. Adamantinoma

Explanation: **Osteoclastoma** - An **osteoclastoma**, also known as a **giant cell tumor of bone**, typically presents in young adults (20-40 years old) and is characterized by a **lytic lesion** often located in the **epiphysis or metaphysis** of long bones, particularly around the knee joint (distal femur or proximal tibia). - These tumors are locally aggressive and can cause pain and swelling. *Simple bone cyst* - A **simple bone cyst (unicameral bone cyst)** is usually found in younger individuals (under 20) and is a **fluid-filled lesion** that often appears as a **central, expansile lytic lesion** in the **metaphysis** of long bones, commonly the proximal humerus or femur, not typically the epiphysis. - These are often painless and discovered incidentally or due to a pathological fracture. *Multiple myeloma* - **Multiple myeloma** is a plasma cell malignancy primarily affecting older adults (typically >50 years old) and presents with **multiple "punched-out" lytic lesions** in various bones (skull, spine, ribs, pelvis), rather than a solitary lytic lesion in a young adult. - It is associated with systemic symptoms such as anemia, hypercalcemia, renal failure, and abnormal immunoglobulins. *Adamantinoma* - An **adamantinoma** is a rare, malignant bone tumor that almost exclusively occurs in the **tibia**, but it typically presents as a **lytic, often eccentric lesion with sclerotic margins** and occasionally a "soap bubble" appearance, and while it occurs in young adults, it is a very rare diagnosis compared to osteoclastoma for a knee lytic lesion. - It often has a characteristic histological appearance resembling epithelial tissue.

Question 7: A young girl presented with swelling of right thigh, with history of trauma 2 months back. Now she presents with swelling at mid-shaft of femur & low grade fever. ESR is mildly raised. X-ray shows a laminated periosteal reaction. Next line of investigation would be:

A. MRI (Correct Answer)
B. Bone scan
C. Blood count & CRP
D. Biopsy

Explanation: ***MRI*** - An **MRI** is the most appropriate next step as it provides excellent detailed imaging of soft tissues and bone marrow, allowing better characterization of the **periosteal reaction**, identifying abscesses, and assessing the extent of bone involvement, crucial for differentiating between infection and tumor. - The presence of a **laminated periosteal reaction** (like an "onion peel") on X-ray, in conjunction with localized swelling and low-grade fever, is highly suggestive of subacute osteomyelitis or even some bone tumors like Ewing sarcoma, for which MRI is superior for defining the extent. *Bone scan* - A **bone scan** (technetium-99m) is sensitive for detecting increased bone turnover, which occurs in infections and tumors, but it is **non-specific**, meaning it cannot differentiate between these conditions. - While it could show increased uptake in the affected area, it would not provide the anatomical detail needed to characterize the lesion or guide further management as effectively as an MRI. *Blood count & CRP* - A **blood count and CRP** would provide information on systemic inflammation (e.g., leukocytosis, elevated CRP for infection), but these are **non-specific**. - While ESR is already mildly raised, these blood tests would confirm generalized inflammation but **cannot localize or characterize the lesion** in the bone, offering little diagnostic value for the specific problem at this stage without imaging. *Biopsy* - A **biopsy** is an invasive procedure and is typically performed after initial imaging studies like X-ray and MRI have characterized the lesion to guide the biopsy site and help determine the nature of the condition (e.g., infection vs. tumor). - Performing a biopsy as the immediate next step without detailed imaging to assess the extent and nature of the lesion would be premature and potentially less effective in diagnosis.

Question 8: An 8 yr old child is having fever with pain and swelling in mid thigh. On Xray lamellated appearance and Codman's triangle is present. Histopathologic examination shows small round cells positive for MIC-2. What is the most likely diagnosis?

A. Chondrosarcoma
B. Chondroblastoma
C. Ewings sarcoma (Correct Answer)
D. Osteosarcoma

Explanation: ***Ewings sarcoma*** - The combination of **fever with pain and swelling** in a child, **lamellated (onion-skin) periosteal reaction**, **Codman's triangle** on X-ray, and **small round cells positive for MIC-2 (CD99)** on histopathology is classic for Ewing's sarcoma. - This highly aggressive bone tumor primarily affects children and young adults, often presenting with systemic symptoms and a diaphyseal or metadiaphyseal location in long bones. *Chondrosarcoma* - This tumor is characterized by the production of **cartilage matrix** and typically affects older adults (40-70 years old), not children. - Radiographically, it often shows **calcifications with rings and arcs** within a lucent lesion, and histopathology reveals chondrocytes, not small round cells positive for MIC-2. *Chondroblastoma* - Chondroblastoma is a rare, **benign cartilage tumor** that typically occurs in the **epiphysis of long bones** in adolescents and young adults. - It usually presents as a well-defined lytic lesion and does not typically show lamellated periosteal reactions or positive MIC-2 staining, nor does it commonly present with fever. *Osteosarcoma* - While osteosarcoma is also an aggressive bone tumor affecting children and adolescents, it is characterized by the production of **osteoid (immature bone)**. - Radiographically, it often presents with a **"sunburst" pattern** due to spiculated periosteal reaction and a **Codman's triangle**, but histopathology shows malignant osteoblasts, not small round cells positive for MIC-2.

Question 9: A patient with metastatic breast cancer presents with pathological fracture of femur. What is the best fixation method?

A. Long Intramedullary Nail (Correct Answer)
B. External Fixator
C. Dynamic Hip Screw
D. Plate and Screws

Explanation: ***Long Intramedullary Nail*** - Provides **strong internal fixation** that can bear weight immediately, crucial for patients with a limited life expectancy due to metastatic disease. - Stabilizes the entire bone, preventing further **pathological fractures** in the diaphysis and allowing earlier mobilization and pain relief. *External Fixator* - Primarily used for **temporary stabilization** in severe open fractures or polytrauma, and not for definitive fixation of pathological fractures. - High risk of **pin tract infections** and patient discomfort, making it unsuitable for long-term management in cancer patients. *Dynamic Hip Screw* - Primarily used for **intertrochanteric hip fractures**, which are typically proximal femur fractures. - Less effective for **diaphyseal fractures** or for stabilizing bone weakened by metastatic disease along its entire length. *Plate and Screws* - While effective for some fractures, plates may not provide sufficient **load-bearing capacity** for extensively lytic or weakened bone in metastatic disease without extensive bone grafting. - Risk of **stress shielding** and subsequent re-fracture proximal or distal to the plate, especially when the intramedullary canal is compromised by tumor.

Question 10: Elderly female present with pain and swelling in the thigh. Xray shows multiple lytic lesions in distal femur with no periosteal reaction. Aspirate from the swelling shows homogenous serosanguinous fluid with RBCs. Which investigation can confirm the diagnosis?

A. S. PTH levels
B. S. Calcium levels
C. CD1a IHC
D. Biopsy (Correct Answer)

Explanation: ***Biopsy*** - A biopsy is the **definitive diagnostic tool** for establishing the presence of malignant cells that would cause lytic lesions and serosanguinous fluid in an elderly patient. - The findings of **multiple lytic lesions** in an elderly patient, coupled with serosanguinous fluid, strongly suggest a primary bone tumor or metastatic disease, which can only be confirmed histologically. *S. PTH levels* - **Elevated PTH** levels are indicative of **hyperparathyroidism**, which can cause bone resorption and lytic lesions (osteitis fibrosa cystica). - However, in this case, the fluid aspirate points towards a more localized, possibly neoplastic process rather than a systemic metabolic bone disorder as the primary concern. *S. Calcium levels* - **Hypercalcemia** can be associated with lytic bone lesions, particularly in cases of malignancy (e.g., **multiple myeloma** or **metastatic cancer**). - While supportive, calcium levels alone are insufficient to **confirm the specific diagnosis** of the underlying cause of the lytic lesions. *CD1a IHC* - **CD1a immunohistochemistry** is primarily used to diagnose **Langerhans cell histiocytosis**, a condition typically seen in children and young adults. - Given the patient's age and the imaging findings of multiple lytic lesions, Langerhans cell histiocytosis is an unlikely diagnosis, making CD1a IHC not the primary or confirming investigation.

Question 11: Which is the commonest true benign bone neoplasm?

A. Hemangioma
B. Osteoid osteoma (Correct Answer)
C. Osteochondroma
D. Enchondroma

Explanation: ***Osteoid osteoma*** - This is one of the most frequently encountered **true benign bone neoplasms**, characterized radiographically by a **nidus** surrounded by sclerotic bone. - It commonly presents with **nocturnal pain** relieved by NSAIDs, often affecting long bones and the posterior elements of the spine. *Hemangioma* - While relatively common, particularly in the **vertebral bodies** and skull, hemangiomas are vascular malformations rather than true primary bone-forming tumors. - They are often asymptomatic and discovered incidentally, appearing as a **"corduroy cloth" pattern** on imaging in the spine. *Osteochondroma* - This is the **most common benign bone tumor overall**, but it is a **cartilage-capped bony exostosis** arising from the external surface of a bone, not a true neoplasm originating within the bone matrix itself. - It is typically found near **growth plates** and can be solitary or multiple (hereditary multiple exostoses). *Enchondroma* - Enchondromas are common **cartilaginous neoplasms** found intramedullary, primarily in the small bones of the hands and feet or in long bones. - While frequent, they are not classified as true bone-forming tumors like osteoid osteoma and can be associated with syndromes like **Ollier's disease** or **Maffucci's syndrome**.

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Principles of Musculoskeletal Oncology

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Staging Systems

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Bone Sarcomas

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Benign Bone Tumors

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Benign Soft Tissue Tumors

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Tumor-Like Conditions

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Surgical Reconstruction After Tumor Resection

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Adjuvant Therapies

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Surveillance Protocols

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