Bone and Soft Tissue Pathology — MCQs

Bone and Soft Tissue Pathology Indian Medical PG Practice Questions and MCQs

Question 21: Which one of the following soft tissue sarcomas frequently metastasizes to lymph nodes?

A. Fibrosarcoma
B. Osteosarcoma
C. Embryonal rhabdomyosarcoma (Correct Answer)
D. Alveolar soft part sarcoma

Explanation: **Explanation:** In general, soft tissue sarcomas are notorious for spreading via the **hematogenous route** (to the lungs) rather than the lymphatic system [1]. However, a specific subset of sarcomas deviates from this rule by frequently metastasizing to **lymph nodes**. **1. Why Embryonal Rhabdomyosarcoma is Correct:** Rhabdomyosarcoma (especially the **Embryonal** and **Alveolar** subtypes) is one of the most common soft tissue sarcomas in children and is well-known for its propensity for lymphatic spread [2]. Approximately 15-25% of patients present with lymph node involvement at the time of diagnosis. This characteristic is a critical factor in surgical staging and treatment planning. **2. Analysis of Incorrect Options:** * **Fibrosarcoma:** This is a classic spindle cell sarcoma that primarily spreads via the bloodstream to the lungs. Lymph node involvement is extremely rare (less than 5%). * **Osteosarcoma:** Although a bone tumor rather than soft tissue, it follows the same rule: it spreads almost exclusively via the hematogenous route, typically presenting with "skip metastases" or pulmonary nodules. * **Alveolar Soft Part Sarcoma:** While this tumor has a very high rate of metastasis, it is famous for spreading to the **brain and lungs** via the blood, often years after the primary tumor is treated. **3. NEET-PG High-Yield Pearls:** To remember the sarcomas that spread to lymph nodes, use the mnemonic **"SCARE"**: * **S:** **S**ynovial sarcoma [2] * **C:** **C**lear cell sarcoma * **A:** **A**ngiosarcoma * **R:** **R**habdomyosarcoma (Embryonal/Alveolar) [2] * **E:** **E**pithelioid sarcoma (The most common to spread to nodes in some series) **Key Concept:** If a question asks for the "most common" sarcoma to spread to lymph nodes in children, think **Rhabdomyosarcoma**; in young adults, think **Epithelioid sarcoma** or **Synovial sarcoma**. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, p. 282. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1222-1226.

Question 22: Ewing's sarcoma is associated with which marker?

A. CD-56 (Correct Answer)
B. CD-38
C. CD-117
D. CD-139

Explanation: **Explanation:** **Ewing’s Sarcoma** is a highly malignant, small round blue cell tumor (SRBCT) primarily affecting children and young adults [1]. It is characterized by the translocation **t(11;22)(q24;q12)**, resulting in the *EWS-FLI1* fusion gene. **Why CD-56 is correct:** While **CD99 (MIC2)** is the most sensitive and classic marker for Ewing’s Sarcoma (showing a characteristic diffuse membranous staining), **CD-56 (Neural Cell Adhesion Molecule - NCAM)** is also frequently expressed. Its presence reflects the neuroectodermal differentiation of the tumor, which was historically categorized under the PNET (Primitive Neuroectodermal Tumor) spectrum. **Analysis of Incorrect Options:** * **CD-38:** This is a marker primarily used for **Plasma Cell Dyscrasias** (e.g., Multiple Myeloma). * **CD-117 (c-KIT):** This is the hallmark marker for **Gastrointestinal Stromal Tumors (GIST)** and is also seen in Mastocytosis and Seminomas [3]. * **CD-138 (Syndecan-1):** (Often confused with CD-139 in distractors) This is another classic marker for **Plasma cells**. **High-Yield Clinical Pearls for NEET-PG:** * **Radiology:** Characterized by an **"Onion-skin"** periosteal reaction. * **Morphology:** Small round blue cells with scanty cytoplasm; **Homer-Wright rosettes** may be seen (indicating neural differentiation). * **PAS Positivity:** The cytoplasm often contains glycogen, making it **PAS positive** and diastase sensitive. * **Genetics:** Over 90% of cases involve **t(11;22)**. * **Differential Diagnosis:** Must be distinguished from other SRBCTs like Lymphoma (CD45+), Rhabdomyosarcoma (Desmin+) [2], and Neuroblastoma (NSE+, Synaptophysin+) [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, pp. 483-484. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1224-1225. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lower Urinary Tract and Male Genital System, pp. 980-982.

Question 23: Which of the following statements is NOT TRUE about synovial sarcoma?

A. It does not arise from synovium.
B. It occurs more commonly at extra-articular sites.
C. It is seen in individuals over 50 years of age. (Correct Answer)
D. Knee and foot are common sites involved.

Explanation: ### Explanation **Synovial Sarcoma** is a misnomer; despite its name, it does not arise from the synovial lining [1]. It is a mesenchymal tumor that accounts for approximately 10% of all soft tissue sarcomas [1]. **1. Why Option C is the correct answer (The False Statement):** Synovial sarcoma characteristically affects **young adults**, typically between the ages of **20 and 40 years** [1]. It is rare in individuals over 50. In the context of NEET-PG, age distribution is a high-yield differentiator for bone and soft tissue tumors. **2. Analysis of other options:** * **Option A (True):** It originates from multipotent mesenchymal stem cells that differentiate into epithelial-like cells, not from pre-existing synovial cells [1]. * **Option B (True):** Only about 10% of these tumors are intra-articular. Most occur in the deep soft tissues of the extremities, near but **outside** the joint capsule [1]. * **Option D (True):** The lower extremities are most commonly involved, with the **knee and thigh** being the most frequent sites, followed by the foot. **3. High-Yield Clinical Pearls for NEET-PG:** * **Genetics:** The hallmark is the **t(X;18)(p11;q11)** translocation, resulting in the **SS18-SSX** fusion gene [1]. This is present in >90% of cases. * **Morphology:** It can be **Biphasic** (contains both spindle cells and gland-like epithelial cells) or **Monophasic** (usually spindle cells only) [1]. * **Immunohistochemistry (IHC):** Positive for **Cytokeratin (CK)** and **EMA** (epithelial markers), which helps distinguish it from other spindle cell sarcomas. * **Radiology:** Often shows "speckled" calcifications on X-ray (seen in 30% of cases). * **Metastasis:** Unlike many sarcomas, it has a higher propensity to spread to **lymph nodes** (along with Rhabdomyosarcoma and Clear Cell Sarcoma). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1225-1226.

Question 24: What is the most common cause of osteoblastic bone metastasis in females?

A. Breast cancer (Correct Answer)
B. Cervical cancer
C. Thyroid cancer
D. Osteosarcoma

Explanation: **Explanation:** **1. Why Breast Cancer is Correct:** In females, **breast cancer** is the most common primary malignancy to metastasize to the bone [1]. While breast cancer often produces mixed (osteolytic and osteoblastic) lesions, it is the **most frequent cause of osteoblastic (sclerotic) metastases in women**. This occurs because tumor cells secrete factors like Bone Morphogenetic Proteins (BMPs) and TGF-β, which stimulate osteoblast proliferation and new bone formation. **2. Why Other Options are Incorrect:** * **Cervical Cancer:** While it can spread to pelvic bones, it is a much less common cause of bone metastasis compared to breast cancer and typically presents as osteolytic lesions. * **Thyroid Cancer:** Follicular thyroid carcinoma frequently metastasizes to bone [1], but these lesions are characteristically **purely osteolytic** and often "pulsatile" in nature. * **Osteosarcoma:** This is a primary bone tumor, not a metastatic process from another organ [2]. While it produces osteoid (bone), it does not fit the category of "metastasis" in this context. **3. High-Yield NEET-PG Pearls:** * **Most common cause of osteoblastic metastasis (Overall & Males):** Prostate Cancer (presents with elevated Serum Acid Phosphatase and PSA) [1]. * **Most common cause of osteolytic metastasis (Adults):** Lung Cancer and Multiple Myeloma [1]. * **Most common site for bone metastasis:** Spine (Vertebrae), followed by the femur and pelvis. * **Imaging Gold Standard:** Bone scan (Technetium-99m) is highly sensitive for osteoblastic activity, whereas PET scans or MRI are better for purely lytic lesions like Myeloma. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Osteoarticular And Connective Tissue Disease, pp. 671-674. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Osteoarticular And Connective Tissue Disease, pp. 673-674.

Question 25: The gene responsible for folic acid transport is situated on which chromosome?

A. Chromosome 10
B. Chromosome 5
C. X Chromosome
D. Chromosome 21 (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. Chromosome 21** The gene responsible for the transport of folic acid into cells is the **SLC19A1 gene** (Solute Carrier Family 19 Member 1), which encodes the **Reduced Folate Carrier (RFC-1)**. This gene is located on the long arm of **Chromosome 21 (21q22.3)**. The clinical significance of this location is particularly relevant in **Down Syndrome (Trisomy 21)**. Because patients with Down Syndrome have three copies of Chromosome 21, they have increased expression of the RFC-1 transporter. This leads to higher intracellular accumulation of methotrexate (a folate antagonist) in leukemic blasts, explaining why children with Down Syndrome and Acute Lymphoblastic Leukemia (ALL) are more sensitive to methotrexate and prone to its toxicity. **Analysis of Incorrect Options:** * **Chromosome 10:** Associated with the *PTEN* gene (Cowden syndrome) and *RET* proto-oncogene (MEN 2). It is not involved in primary folate transport. * **Chromosome 5:** Home to the *APC* gene (Familial Adenomatous Polyposis). While 5q deletions are seen in Myelodysplastic Syndrome, it does not house the primary folate transporter gene. * **X Chromosome:** Associated with conditions like Hemophilia and Duchenne Muscular Dystrophy. Folate transport deficiency (Hereditary Folate Malabsorption) is typically autosomal recessive, not X-linked. **High-Yield Clinical Pearls for NEET-PG:** * **SLC19A1/RFC-1:** Located on Chromosome 21; primary transporter for reduced folates and methotrexate. * **Down Syndrome & ALL:** Increased RFC-1 expression leads to methotrexate sensitivity. * **CBS Gene:** The Cystathionine Beta-Synthase gene is also on Chromosome 21. Its overexpression in Down Syndrome leads to decreased homocysteine levels (the opposite of homocystinuria). * **Hereditary Folate Malabsorption:** Caused by mutations in the *SLC46A1* gene (Proton-coupled folate transporter) on Chromosome 17.

Question 26: Storiform growth pattern is seen in which of the following tumors?

A. Malignant fibrous histiocytoma
B. Solitary fibrous tumor
C. Dermatofibrosarcoma protuberans
D. All of the above (Correct Answer)

Explanation: The **storiform pattern** (derived from the Latin word *storea*, meaning straw mat) is a classic histopathological arrangement where spindle cells radiate from a central point, resembling a cartwheel or a woven mat. ### **Explanation of Options** * **Malignant Fibrous Histiocytoma (MFH):** Now more commonly classified as Undifferentiated Pleomorphic Sarcoma (UPS), this tumor is the "classic" example of a storiform-pleomorphic pattern. It features high-grade spindle cells arranged in prominent cartwheel configurations. * **Dermatofibrosarcoma Protuberans (DFSP):** This is a low-to-intermediate grade malignancy of the dermis. It is characterized by a highly uniform, "monomorphous" storiform pattern. The spindle cells are often described as having a "pinwheel" appearance and characteristically infiltrate the subcutaneous fat in a "honeycomb" pattern. * **Solitary Fibrous Tumor (SFT):** While SFT is famous for its "patternless pattern" (haphazardly arranged spindle cells with staghorn vessels), it frequently exhibits focal areas of storiform growth, especially in more cellular variants. Since all three tumors can exhibit this architectural arrangement, **Option D** is the correct answer. ### **High-Yield Clinical Pearls for NEET-PG** * **DFSP Marker:** CD34 positive (very high yield). It is associated with the translocation **t(17;22)** involving the *COL1A1* and *PDGFB* genes. * **SFT Marker:** **STAT6** is the most specific immunohistochemical marker (due to *NAB2-STAT6* fusion). * **Other Storiform Tumors:** Benign Fibrous Histiocytoma (Dermatofibroma) also shows a prominent storiform pattern [1]. * **Differential Diagnosis:** If you see "Herringbone pattern," think **Fibrosarcoma**. If you see "Verocay bodies/Antoni A," think **Schwannoma** [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, pp. 1160-1162. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Peripheral Nerves and Skeletal Muscles, p. 1250.

Question 27: Synovial sarcomas typically spread by which route?

A. Hematogenous route
B. Lymphatic route (Correct Answer)
C. Drop metastasis
D. It does not metastasize; it is a locally invasive tumor

Explanation: **Explanation:** **1. Why Option B is Correct:** In general pathology, a fundamental rule is that **carcinomas** spread via lymphatics and **sarcomas** spread via the hematogenous (blood) route [2]. However, there are specific exceptions to this rule that are high-yield for exams. **Synovial sarcoma** is one of the few sarcomas that shows a high propensity for **lymphatic spread** (seen in up to 20-25% of cases). Other sarcomas following this exception include Rhabdomyosarcoma, Clear cell sarcoma, Epithelioid sarcoma, and Angiosarcoma (Mnemonic: **SREC**A). **2. Why Other Options are Incorrect:** * **Option A (Hematogenous):** While synovial sarcoma can spread to the lungs via the blood [2], the question asks for its *typical* or distinguishing feature among sarcomas. Its tendency for lymphatic involvement is its defining metastatic characteristic in competitive exams. * **Option C (Drop Metastasis):** This refers to seeding via cerebrospinal fluid (CSF), typically seen in CNS tumors like Medulloblastoma or Ependymoma. * **Option D (Locally invasive):** This is incorrect because Synovial Sarcoma is a highly aggressive, high-grade malignant tumor with a high potential for distant metastasis. **3. NEET-PG High-Yield Pearls:** * **Cytogenetics:** Characterized by the translocation **t(x;18)(p11;q11)**, resulting in the *SS18-SSX* fusion gene [1]. * **Histology:** Can be **Biphasic** (spindle cells and epithelial-like glands) or **Monophasic** (spindle cells only) [1]. * **Immunohistochemistry (IHC):** Positive for **Cytokeratin (CK)** and **EMA**, which is unusual for a mesenchymal tumor. * **Location:** Despite the name, it rarely arises *within* the joint cavity; it usually occurs in the soft tissues near large joints (especially the knee) [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1225-1226. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, p. 282.

Question 28: Peripheral giant cell granuloma occurs most commonly on which of the following locations?

A. Gingiva (Correct Answer)
B. Alveolar ridge
C. Palate
D. Floor of the mouth

Explanation: **Explanation:** **Peripheral Giant Cell Granuloma (PGCG)** is a common reactive exophytic lesion of the oral cavity, representing a local response to chronic irritation or trauma. 1. **Why Gingiva is Correct:** The PGCG originates specifically from the **periosteum or the periodontal ligament**. Because these tissues are anatomically associated with the tooth-bearing areas, the lesion occurs exclusively on the **gingiva** (usually the interdental papilla) or the edentulous **alveolar ridge**. Between the two, the gingiva is the most frequent site of involvement. 2. **Why Other Options are Incorrect:** * **Alveolar Ridge:** While PGCG can occur here in edentulous patients, it is statistically less common than the gingival presentation in dentate individuals. * **Palate and Floor of the Mouth:** These sites lack the periodontal ligament and the specific periosteal environment required for PGCG formation. Lesions found here are more likely to be Pyogenic Granulomas or Irritation Fibromas. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Appearance:** It typically presents as a firm, reddish-blue or "liver-colored" nodule. The dark color is due to prominent vascularity and hemorrhage. * **Histopathology:** Characterized by a non-encapsulated proliferation of **multinucleated giant cells** in a background of ovoid to spindle-shaped mesenchymal cells, with prominent **hemosiderin deposits**. * **Radiology:** While "peripheral" (soft tissue), it may cause "cupping" or superficial resorption of the underlying alveolar bone. * **Differential Diagnosis:** Must be distinguished from **Central Giant Cell Granuloma (CGCG)**, which is an intraosseous lesion, and the "Brown Tumor" of hyperparathyroidism (biochemical correlation with Serum Calcium/PTH is essential).

Question 29: Narrow, high arched palate, prolonged retention of deciduous teeth, and failure in the eruption of permanent teeth are characteristic of which condition?

A. Cherubism
B. Cleidocranial dysplasia (Correct Answer)
C. Paget's disease
D. Marfan syndrome

Explanation: ### Explanation **Cleidocranial Dysplasia (CCD)** is an autosomal dominant skeletal disorder caused by a mutation in the **RUNX2 (CBFA1) gene**, which is essential for osteoblast differentiation and bone formation [1]. The condition primarily affects bones formed by intramembranous ossification. **Why Option B is Correct:** The hallmark of CCD is the triad of **clavicular hypoplasia/aplasia** (allowing patients to touch their shoulders in the midline), delayed closure of cranial sutures (leading to frontal bossing), and significant dental anomalies [1]. The dental features specifically mentioned—**narrow, high-arched palate**, **prolonged retention of deciduous teeth**, and **failure of permanent teeth to erupt** (often due to multiple **supernumerary teeth**)—are pathognomonic for this condition [1]. **Why Other Options are Incorrect:** * **Cherubism:** Characterized by bilateral, painless, symmetrical swelling of the jaws (mandible > maxilla) due to giant cell lesions. It does not typically present with a high-arched palate or clavicular issues. * **Paget’s Disease:** A disorder of bone remodeling (excessive resorption and formation) seen in older adults. It causes "cotton wool" skull appearance and enlargement of the maxilla (leontiasis ossea), but not retention of deciduous teeth. * **Marfan Syndrome:** While it features a high-arched palate and skeletal abnormalities (arachnodactyly, pectus excavatum), it is primarily a connective tissue disorder (Fibrillin-1 mutation) and does not cause the specific dental eruption failures seen in CCD. **High-Yield Clinical Pearls for NEET-PG:** * **Gene:** *RUNX2* (Chromosome 6p21) [1]. * **Radiology:** Presence of **Wormian bones** (extra sutural bones in the skull) [1]. * **Dental:** Multiple impacted supernumerary teeth (often a "third dentition") [1]. * **Key Sign:** Ability to approximate shoulders anteriorly due to absent clavicles. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, p. 1186.

Question 30: What is a common complication seen in a patient with osteopetrosis during tooth extraction?

A. Jaw fracture
B. Osteomyelitis
C. Both jaw fracture and osteomyelitis (Correct Answer)
D. None of the above

Explanation: **Explanation:** **Osteopetrosis** (Marble Bone Disease) is a genetic disorder characterized by defective **osteoclast-mediated bone resorption**. This leads to an overgrowth of dense, sclerotic bone that is paradoxically weak and prone to complications. **Why Option C is correct:** 1. **Jaw Fracture:** Although the bones appear dense on X-ray, they lack the normal trabecular architecture and organic matrix flexibility [1]. This makes the bone extremely **brittle**. The mechanical force required for tooth extraction often exceeds the bone's threshold, leading to iatrogenic fractures. 2. **Osteomyelitis:** The excessive bone deposition encroaches upon the medullary cavity, significantly reducing the vascular supply (**avascularity**) [1]. In the jaw, where the oral cavity provides a constant source of bacteria, the lack of adequate blood flow prevents an effective immune response and healing, leading to refractory osteomyelitis following dental procedures. **Analysis of other options:** * **Option A & B:** While both are individual complications, they frequently occur concurrently or as a sequence of events in osteopetrosis patients. **High-Yield NEET-PG Pearls:** * **Pathogenesis:** Mutation in the **TCIRG1 gene** (vacuolar ATPase proton pump) or **CLCN7** (chloride channel) prevents the acidification required for bone resorption. * **Radiology:** Classic "Erlenmeyer flask deformity" of long bones and "Rugger-jersey spine" [1]. * **Hematology:** Encroachment on the marrow space leads to **pancytopenia** and extramedullary hematopoiesis (hepatosplenomegaly) [1]. * **Neurology:** Narrowing of cranial foramina can cause cranial nerve palsies (e.g., blindness or deafness) [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1188-1189.

Practice by Chapter

Bone Development and Growth

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Fracture Healing

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Osteomyelitis and Infectious Diseases

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Metabolic Bone Diseases

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Bone Tumors and Tumor-like Lesions

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Joints and Rheumatologic Diseases

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Soft Tissue Tumors

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Muscular Dystrophies and Myopathies

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Diseases of Tendons and Fascia

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Pathology of Orthopedic Implants

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