Bone Tumors Practice Questions

Q: A patient presents with a lytic lesion in an X-ray of the upper end of the humerus. What is the most likely diagnosis?

Unicameral bone cyst. ### Explanation **Correct Answer: C. Unicameral Bone Cyst (UBC)** The **Unicameral Bone Cyst (Simple Bone Cyst)** is the most common cause of a well-defined, solitary lytic lesion in the proximal humerus of a skeletally immature patient. * **Pathophysiology:** It is a fluid-filled cavity (not a true neoplasm) typically located in the **metaphysis** of long bones, immediately adjacent to the growth plate. As the child grows, the cyst appears to "migrate" toward the diaphysis. * **Radiological Hallmark:** It presents as a centrally located, geographic lytic lesion with thinning of the cortex. A pathognomonic sign is the **"Fallen Leaf Sign,"** where a cortical fragment settles at the bottom of the cyst following a pathological fracture. **Why the other options are incorrect:** * **A. Osteosarcoma:** This is a malignant bone-forming tumor. Radiologically, it presents with bone destruction, a **"Sunburst appearance,"** and periosteal reactions like **Codman’s triangle**, rather than a simple lytic cyst. * **B. Osteochondroma:** This is the most common benign bone tumor. It presents as a **bony outgrowth (exostosis)** with a cartilage cap, either pedunculated or sessile, pointing away from the joint. It is not a lytic lesion. * **D. Osteoclastoma (Giant Cell Tumor):** While it is a lytic lesion, it typically occurs in **skeletally mature** patients (20–40 years) and is characteristically **epiphyseal** in location with a "Soap bubble appearance." **High-Yield Clinical Pearls for NEET-PG:** * **Most common site for UBC:** Proximal Humerus > Proximal Femur. * **Fallen Leaf Sign:** Diagnostic of UBC after a fracture. * **Treatment:** Observation or aspiration/injection of corticosteroids (Methylprednisolone). Curettage and bone grafting are reserved for large, symptomatic cysts. * **Aneurysmal Bone Cyst (ABC):** Differentiated from UBC by its eccentric location and "fluid-fluid levels" on MRI.

Q: Sun burst appearance is seen in which of the following conditions?

Osteosarcoma. ### Explanation **Correct Answer: A. Osteosarcoma** **Why it is correct:** The "Sunburst appearance" is a classic radiological sign of **Osteosarcoma**, the most common primary malignant bone tumor in children and adolescents. This appearance occurs due to an aggressive **periosteal reaction**. When the tumor grows rapidly, it lifts the periosteum and stretches the Sharpey’s fibers. New bone is deposited along these fibers perpendicular to the bone surface, creating thin, radiating spicules of calcification that resemble the rays of a sun. **Why the other options are incorrect:** * **B. Osteopetrosis:** Characterized by increased bone density due to defective osteoclast function. Typical radiological signs include "Marble bone disease," "Bone-within-bone" appearance, and "Erlenmeyer flask deformity." * **C. Osteomyelitis:** Chronic osteomyelitis typically shows an **Involucrum** (new bone formation around dead bone) and a **Sequestrum** (dead bone). While it can cause periosteal reaction, it is usually laminated or irregular, not sunburst. * **D. Osteoradionecrosis:** This is a complication of radiation therapy (common in the mandible). It presents as bone death with ill-defined lucencies and cortical destruction, but lacks the aggressive perpendicular spicules of a sunburst pattern. **High-Yield Clinical Pearls for NEET-PG:** * **Codman’s Triangle:** Another periosteal reaction seen in Osteosarcoma (and Ewing’s) where the periosteum is lifted at the edge of the tumor. * **Location:** Most common site is the **Metaphysis** of long bones (especially around the knee). * **Ewing’s Sarcoma:** Classically shows an **"Onion-peel"** (laminated) periosteal reaction. * **Osteoid Osteoma:** Characterized by a **Nidus** (radiolucent zone) surrounded by sclerotic bone, with pain relieved by Aspirin.

Q: A 20-year-old boy complains of pain in his leg at a particular site, worst at night and relieved by salicylates. What is the most likely diagnosis?

Osteoid osteoma. ### Explanation The clinical presentation described is a classic textbook case of **Osteoid Osteoma**. **1. Why Osteoid Osteoma is correct:** Osteoid osteoma is a small, benign, bone-forming tumor characterized by a central "nidus" (less than 2 cm) of osteoid tissue. The hallmark symptom is **nocturnal pain** (worse at night). This occurs because the nidus produces high levels of **Prostaglandins (PGE2 and PGI2)**, which cause local vasodilation and nerve stimulation. Since **Salicylates (Aspirin/NSAIDs)** inhibit prostaglandin synthesis, they provide dramatic and characteristic relief, serving as a key diagnostic clue. **2. Why other options are incorrect:** * **Osteosarcoma:** This is a highly malignant tumor. While it causes pain, the pain is usually constant, progressive, and associated with a rapidly enlarging soft tissue mass and systemic symptoms, rather than specific relief with aspirin. * **Osteoclastoma (Giant Cell Tumor):** This typically occurs in a slightly older age group (20–40 years) and is located at the epiphysis. It presents with dull aching pain and swelling, but lacks the prostaglandin-mediated nocturnal pain pattern. **3. High-Yield Clinical Pearls for NEET-PG:** * **Radiology:** The classic finding is a small, radiolucent **nidus** surrounded by a large zone of dense, reactive **sclerotic bone**. * **Common Site:** Femur (proximal) and Tibia (diaphysis) are the most common locations. * **Treatment of Choice:** If medical management (NSAIDs) fails, **Radiofrequency Ablation (RFA)** is the gold standard. * **Differential Diagnosis:** **Osteoblastoma** is similar but larger (>2 cm), usually involves the spine, and the pain is *not* typically relieved by aspirin.

Q: What is the most common site of metastases of osteosarcoma?

Lung. **Explanation:** **1. Why Lung is the Correct Answer:** Osteosarcoma is a highly malignant primary bone tumor characterized by the production of osteoid. Its primary mode of spread is **hematogenous** (via the bloodstream). Because the venous drainage from the limbs (where most osteosarcomas occur) passes directly into the systemic circulation and reaches the pulmonary capillary bed first, the **lungs** are the most common site of distant metastasis. Approximately 80% of patients who develop metastatic disease will have pulmonary involvement. These metastases often appear as "cannonball" lesions on imaging and can undergo ossification. **2. Why Other Options are Incorrect:** * **Liver and Spleen (A & B):** While osteosarcoma can spread to solid abdominal organs, this is rare and typically occurs only in the very late, terminal stages of disseminated disease. * **Lymph Nodes (C):** Unlike carcinomas, sarcomas (including osteosarcoma) rarely spread via the lymphatic system. Only about 3-5% of osteosarcoma cases show regional lymph node involvement. (Note: Exceptions among sarcomas that *do* spread to lymph nodes include Rhabdomyosarcoma, Clear cell sarcoma, and Epithelioid sarcoma). **3. Clinical Pearls for NEET-PG:** * **Skip Metastasis:** This refers to a second smaller lesion within the same bone or across a joint, occurring in the same limb. It indicates a poor prognosis. * **Investigation of Choice:** For the primary lesion, **MRI** is preferred to assess local extent. For detecting lung metastases, a **High-Resolution CT (HRCT) of the Chest** is the gold standard. * **Prognostic Factor:** The presence of lung metastasis at the time of diagnosis is the most significant negative prognostic factor. * **Sunray Appearance/Codman’s Triangle:** Classic radiological signs of osteosarcoma due to periosteal reaction.

Q: Which of the following is NOT true about diaphyseal aclasia?

It is autosomal recessive.. **Explanation:** **Diaphyseal Aclasia**, also known as **Multiple Hereditary Exostoses (MHE)**, is a genetic condition characterized by the growth of multiple osteochondromas. 1. **Why Option B is the correct answer (The False Statement):** Diaphyseal aclasia is an **Autosomal Dominant** condition, not recessive. It is primarily caused by mutations in the **EXT1** (Chromosome 8) or **EXT2** (Chromosome 11) genes, which are involved in the synthesis of heparan sulfate. 2. **Analysis of other options:** * **Option A:** It is synonymous with Multiple Hereditary Exostosis. The term "diaphyseal aclasia" refers to the failure of normal remodeling of the shaft (diaphysis) during growth. * **Option C:** It is frequently associated with **Madelung deformity** (shortening/bowing of the radius with dorsal subluxation of the distal ulna) and other growth disturbances like coxa valga and limb length discrepancy. * **Option D:** Although the name suggests "diaphyseal," the exostoses actually arise from the **metaphysis** near the growth plate. As the bone grows, they appear to migrate toward the diaphysis. **High-Yield Clinical Pearls for NEET-PG:** * **Inheritance:** Autosomal Dominant (Most common skeletal dysplasia). * **Malignant Transformation:** There is a **1–5% risk** of transformation into **Chondrosarcoma** (suspect if there is sudden pain or a cartilage cap thickness >2 cm in adults). * **Direction of Growth:** The exostoses always grow **away from the joint** (the "fleeing from the knee" and "seeking the elbow" rule). * **Histology:** Characterized by a benign cartilaginous cap covering a bony stalk that is continuous with the marrow cavity of the host bone.

Q: Which of the following conditions is least likely to present as an acentric osteolytic lesion?

Simple bone cyst. **Explanation:** The key to solving this question lies in understanding the **location** of the lesion within the transverse plane of the bone. **1. Why Simple Bone Cyst (SBC) is the correct answer:** A Simple Bone Cyst (also known as a Unicameral Bone Cyst) is classically a **centrally located**, symmetric, radiolucent lesion. It typically occurs in the metaphyseal region of long bones (most commonly the proximal humerus and femur). As the bone grows, the cyst may appear to move toward the diaphysis, but it maintains its central orientation. A characteristic radiographic finding is the "Fallen Leaf sign" following a pathological fracture. **2. Analysis of Incorrect Options (Acentric Lesions):** * **Aneurysmal Bone Cyst (ABC):** These are characteristically **eccentric (acentric)**, expansile, "soap-bubble" lesions that often cause cortical thinning and "ballooning" of the bone. * **Giant Cell Tumor (GCT):** GCTs are typically **eccentric** and subarticular (extending to the subchondral plate). They occur in the epiphysis after the physis has closed. * **Fibrous Cortical Defect (FCD):** As the name suggests, these are small, cortical-based lesions. They are located **peripherally/eccentrically** within the metaphyseal cortex and are usually asymptomatic incidental findings in children. **High-Yield Clinical Pearls for NEET-PG:** * **Central Lesions:** Simple Bone Cyst, Enchondroma (usually central in small bones). * **Eccentric Lesions:** ABC, GCT, Osteosarcoma, Fibrous Dysplasia, Non-Ossifying Fibroma (NOF). * **Epiphyseal Lesions:** GCT (after plate closure), Chondroblastoma (before plate closure). * **Diaphyseal Lesions:** Ewing’s Sarcoma, Osteoid Osteoma, Adamantinoma. * **Soap-bubble appearance:** Classically seen in GCT and ABC.

Q: What is the commonest true benign tumor of bone?

Osteoid osteoma. ### Explanation **Correct Answer: C. Osteoid osteoma** **Why it is correct:** Osteoid osteoma is considered the **most common true benign bone tumor**. While Osteochondroma is technically more frequent, it is pathologically classified as a developmental anomaly (physeal dysplasia) rather than a true neoplasm. Osteoid osteoma typically presents in the 2nd decade of life, most commonly in the femur or tibia. It is characterized by a small radiolucent **nidus** (less than 2 cm) surrounded by dense reactive sclerosis. **Why the other options are incorrect:** * **A. Osteoblastoma:** Often called a "giant osteoid osteoma" (nidus >2 cm), it is much rarer. It primarily affects the posterior elements of the spine and lacks the characteristic nocturnal pain relieved by NSAIDs. * **B. Chondroblastoma:** A rare benign cartilaginous tumor. Its distinguishing feature is its **epiphyseal** location in young patients (skeletally immature), but it is far less common than osteoid osteoma. * **C. Giant Cell Tumor (GCT):** While common, GCT is classified as a **locally aggressive** tumor rather than a simple "true benign" tumor. It occurs in the epiphysis of skeletally mature adults (20–40 years) and has a high recurrence rate. **High-Yield Clinical Pearls for NEET-PG:** * **Classic Presentation:** Severe nocturnal pain that is **dramatically relieved by Aspirin or NSAIDs** (due to high prostaglandin levels in the nidus). * **Radiology:** "Nidus" with surrounding sclerosis. On bone scan, it shows the **"Double density sign."** * **Most common site:** Proximal Femur. * **Treatment:** Medical management with NSAIDs is first-line; if refractory, **Radiofrequency Ablation (RFA)** is the gold standard.

Q: Osteochondroma is a disease of which part of the bone?

Metaphysis. **Explanation:** **Osteochondroma** (also known as Exostosis) is the most common benign bone tumor. It is fundamentally a developmental anomaly rather than a true neoplasm. **1. Why Metaphysis is Correct:** Osteochondromas arise from the **metaphysis** of long bones, most commonly around the knee (distal femur and proximal tibia). The pathogenesis involves the displacement of a fragment of the **epiphyseal growth plate** toward the metaphysis. As the bone grows, this displaced cartilage continues to proliferate and ossify, creating a bony outgrowth (stalk) covered by a cartilaginous cap. Because it originates from the growth plate and moves away with longitudinal growth, it is always found in the metaphyseal region. **2. Why Other Options are Incorrect:** * **Diaphysis:** While the tumor may appear to move toward the shaft as the bone grows, its origin is never the primary diaphysis. Common diaphyseal tumors include Ewing’s Sarcoma and Adamantinoma. * **Epiphysis:** Tumors here are rare. The classic epiphyseal tumor is the Giant Cell Tumor (GCT) or Chondroblastoma. * **Periosteum:** Although the tumor is covered by periosteum, it does not originate from it; it is a growth of the underlying bone and cartilage. **3. High-Yield Clinical Pearls for NEET-PG:** * **Radiological Sign:** The pathognomonic feature is **corticomedullary continuity** (the cortex and medulla of the tumor are continuous with the host bone). * **Direction of Growth:** The tumor always grows **away from the joint** (the "pointing away" sign). * **Malignant Transformation:** Occurs in 2 cm** in adults suggests transformation to Chondrosarcoma. * **Genetic Association:** Mutations in **EXT1 and EXT2** genes.

Q: A bone tumor seen in children presents with a characteristic lamellated periosteal reaction and a mottled appearance, with extension into soft tissue. Which of the following is the most likely diagnosis?

Ewing's sarcoma. **Explanation:** **Ewing’s Sarcoma** is the correct diagnosis based on the classic triad of clinical and radiological findings presented: 1. **Age:** It is most common in children and adolescents (typically 5–15 years). 2. **Radiological Appearance:** The "mottled appearance" refers to a permeative, moth-eaten pattern of bone destruction. The characteristic **lamellated periosteal reaction** is famously known as the **"Onion-skin" appearance**, caused by the rapid, rhythmic push of the tumor against the periosteum. 3. **Soft Tissue Involvement:** It frequently presents with a large associated soft tissue mass. **Why other options are incorrect:** * **Osteosarcoma:** While also common in children, it typically shows a **"Sunburst" appearance** or **Codman’s triangle** on X-ray, rather than lamellated layers. It usually involves the metaphysis, whereas Ewing’s often involves the diaphysis. * **Giant Cell Tumor (GCT):** This is a tumor of young adults (20–40 years) and is characterized by an **eccentric, "Soap-bubble" appearance** at the epiphysis. * **Osteoid Osteoma:** This is a small, benign lesion characterized by a **radiolucent nidus** (less than 2 cm) surrounded by dense reactive sclerosis, typically causing nocturnal pain relieved by aspirin. **High-Yield Clinical Pearls for NEET-PG:** * **Origin:** Ewing’s sarcoma arises from primitive neuroectodermal cells (small round blue cell tumor). * **Genetics:** Associated with **t(11;22)** translocation involving the *EWS-FLI1* gene. * **Site:** Most common site is the **diaphysis** of long bones (Femur > Tibia > Humerus). * **Clinical Mimic:** It often presents with fever and elevated ESR, frequently mimicking **Osteomyelitis**.

Q: Which of the following is NOT a malignant bone tumor?

Aneurysmal bone cyst. **Explanation:** The correct answer is **C. Aneurysmal bone cyst (ABC)**. In orthopaedic oncology, tumors are classified based on their biological behavior as benign, locally aggressive, or malignant. **Why Aneurysmal Bone Cyst is the correct answer:** An Aneurysmal Bone Cyst is a **benign, non-neoplastic** reactive bone lesion characterized by blood-filled, cystic spaces separated by connective tissue septa. While it can be locally destructive and "expansile," it does not metastasize and is not a true malignancy. Radiologically, it presents with a "soap bubble" appearance and classic "fluid-fluid levels" on MRI. **Analysis of other options:** * **A. Osteosarcoma:** This is the most common **primary malignant** bone tumor in children and adolescents. It is characterized by the production of osteoid (immature bone) by malignant cells. * **B. Giant Cell Tumor (GCT):** While GCT is often classified as "benign but locally aggressive," it is technically a neoplasm. However, in the context of this question, ABC is a clearly benign cyst, whereas GCT can occasionally metastasize to the lungs (malignant GCT). *Note: If both ABC and GCT are options, ABC is the "more" benign entity.* * **D. Chondrosarcoma:** This is a **malignant** tumor of cartilage-producing cells, typically seen in older adults. **NEET-PG High-Yield Pearls:** * **Fluid-fluid levels:** Pathognomonic for ABC on MRI (though also seen in Telangiectatic Osteosarcoma). * **Location of ABC:** Usually metaphysis of long bones or posterior elements of the spine. * **Treatment of ABC:** Curettage and bone grafting; however, it has a high recurrence rate. * **Sunburst appearance/Codman’s triangle:** Classic radiological signs of Osteosarcoma.

Question 1

A patient presents with a lytic lesion in an X-ray of the upper end of the humerus. What is the most likely diagnosis?

Accepted Answer

Unicameral bone cyst

Answer

Osteosarcoma

Answer

Osteochondroma

Answer

Osteoclastoma

Question 2

Sun burst appearance is seen in which of the following conditions?

Accepted Answer

Osteosarcoma

Answer

Osteopetrosis

Answer

Osteomyelitis

Answer

Osteoradionecrosis

Question 3

A 20-year-old boy complains of pain in his leg at a particular site, worst at night and relieved by salicylates. What is the most likely diagnosis?

Accepted Answer

Osteoid osteoma

Answer

Osteosarcoma

Answer

Osteoclastoma

Answer

None of the above

Question 4

What is the most common site of metastases of osteosarcoma?

Accepted Answer

Lung

Answer

Liver

Answer

Spleen

Answer

Lymph nodes

Question 5

Which of the following is NOT true about diaphyseal aclasia?

Accepted Answer

It is autosomal recessive.

Answer

It is multiple hereditary exostosis.

Answer

It is associated with Madelung deformity.

Answer

The exostoses arise from the metaphysis.

Question 6

Which of the following conditions is least likely to present as an acentric osteolytic lesion?

Accepted Answer

Simple bone cyst

Answer

Aneurysmal bone cyst

Answer

Giant cell tumor

Answer

Fibrous cortical defect

Question 7

What is the commonest true benign tumor of bone?

Accepted Answer

Osteoid osteoma

Answer

Osteoblastoma

Answer

Chondroblastoma

Answer

Giant Cell Tumor (GCT)

Question 8

Osteochondroma is a disease of which part of the bone?

Accepted Answer

Metaphysis

Answer

Diaphysis

Answer

Epiphysis

Answer

Periosteum

Question 9

A bone tumor seen in children presents with a characteristic lamellated periosteal reaction and a mottled appearance, with extension into soft tissue. Which of the following is the most likely diagnosis?

Accepted Answer

Ewing's sarcoma

Answer

Osteosarcoma

Answer

Giant cell tumor

Answer

Osteoid osteoma

Question 10

Which of the following is NOT a malignant bone tumor?

Accepted Answer

Aneurysmal bone cyst

Answer

Osteosarcoma

Answer

Giant cell tumor (Osteoclastoma)

Answer

Chondrosarcoma

Bone Tumors — MCQs

Bone Tumors — MCQs

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