Bone and Soft Tissue Pathology Practice Questions

Q: Which of the following is a spindle cell tumor?

Alveolar soft tissue sarcoma. **Explanation:** The question asks to identify which tumor is **not** a spindle cell tumor (implied by the selection of Alveolar Soft Part Sarcoma as the correct answer, as the others are classic spindle cell neoplasms). **1. Why Alveolar Soft Part Sarcoma (ASPS) is the correct answer:** ASPS is characterized by a **nested (organoid) or pseudoalveolar growth pattern**, not a spindle cell morphology. The cells are large, polygonal, and have abundant eosinophilic granular cytoplasm. A high-yield feature is the presence of **PAS-positive, diastase-resistant rhomboid-shaped crystals** in the cytoplasm. It is associated with the **t(X;17)** translocation involving the *ASPSCR1-TFE3* gene fusion. **2. Why the other options are incorrect:** * **Leiomyoma:** A benign smooth muscle tumor composed of fascicles of **spindle cells** with "cigar-shaped" nuclei and blunt ends. * **Schwannoma:** A peripheral nerve sheath tumor consisting of **spindle cells** arranged in dense (Antoni A) and loose (Antoni B) areas [1]. Verocay bodies (palisading nuclei) are a hallmark [1]. * **Fibrous Histiocytoma:** Typically presents as a "storiform" (mat-like) arrangement of **spindle-shaped fibroblasts** and myofibroblasts. **NEET-PG High-Yield Pearls:** * **Spindle Cell Tumors Mnemonic:** "S-L-I-F-E" (Schwannoma, Leiomyoma/sarcoma, Infantile fibrosarcoma, Fibrosarcoma, Ewing’s - though Ewing's is usually small round blue cell, it can occasionally mimic spindles). * **ASPS Clinical Fact:** Despite being slow-growing, it has a high propensity for early **hematogenous metastasis**, particularly to the **lungs and brain**. * **IHC for ASPS:** Strong nuclear expression of **TFE3** is the most sensitive and specific marker. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Peripheral Nerves and Skeletal Muscles, pp. 1248-1250.

Q: Needle-shaped crystals that are negatively birefringent on polarized microscopy are characteristic of which crystal-associated arthropathy?

Gout. ### Explanation The correct answer is **Gout**. **1. Why Gout is Correct:** Gout is a crystal-induced arthropathy caused by the deposition of **Monosodium Urate (MSU)** crystals in the joints. Under polarized light microscopy, these crystals exhibit two pathognomonic features: * **Morphology:** They are thin, **needle-shaped**. * **Birefringence:** they show **strong negative birefringence**. This means they appear **yellow** when aligned parallel to the slow axis of the compensator and blue when perpendicular. **2. Why Other Options are Incorrect:** * **CPPD (Pseudogout):** These crystals are **rhomboid or brick-shaped** and exhibit **weak positive birefringence** (appearing blue when parallel to the compensator). * **Neuropathic Arthropathy (Charcot Joint):** This is a progressive joint destruction due to loss of pain and proprioception (commonly in Diabetes). It is characterized by the "6 Ds" (Destruction, Debris, Disorganization, etc.) rather than specific crystals. * **Hemophilic Arthropathy:** This results from recurrent intra-articular bleeding (hemarthrosis). Diagnosis is based on clinical history and synovial thickening/hemosiderin deposition on MRI, not crystals. **3. NEET-PG High-Yield Pearls:** * **Gold Standard Diagnosis:** Synovial fluid analysis under polarized microscopy is the definitive test for Gout. * **Radiology:** Look for "Punched-out" erosions with overhanging edges (**Martel’s sign**). * **Acute Management:** NSAIDs (first-line), Colchicine, or Corticosteroids. * **Chronic Management:** Xanthine oxidase inhibitors like **Allopurinol** (do not start during an acute attack as it may worsen symptoms). * **Mnemonic:** **N**eedle **N**egative (**N-N**) for Gout.

Q: What is the most common soft tissue tumor in adults?

Liposarcoma. **Explanation:** **Liposarcoma** is currently recognized as the most common soft tissue sarcoma (STS) in adults, accounting for approximately 20–25% of all adult sarcomas. These tumors typically arise from adipocytes and are most frequently found in the retroperitoneum and the lower extremities (thigh). Histologically, the presence of **lipoblasts** is a characteristic feature. **Analysis of Options:** * **Liposarcoma (Correct):** It has overtaken Malignant Fibrous Histiocytoma (MFH) in recent classifications as the most frequent subtype. The most common histological variant is the well-differentiated liposarcoma. * **Embryonal Rhabdomyosarcoma (Incorrect):** This is the most common soft tissue sarcoma in **children** (0–14 years), typically occurring in the head, neck, and genitourinary tract. * **Synovial Sarcoma (Incorrect):** This is a common sarcoma in young adults (15–40 years), often occurring near joints (though not arising from the synovium itself). It is characterized by the **t(X;18)** translocation. * **Malignant Fibrous Histiocytoma (Incorrect):** Formerly considered the most common, this diagnosis is now largely obsolete. Most tumors previously labeled as MFH are now reclassified as **Pleomorphic Undifferentiated Sarcoma (PUS)** or specific subtypes of liposarcoma/leiomyosarcoma. **High-Yield NEET-PG Pearls:** * **Most common STS in Children:** Rhabdomyosarcoma. * **Most common STS in Adults:** Liposarcoma. * **Most common site for STS:** Lower extremity (Thigh). * **Route of spread:** Most sarcomas spread **hematogenously** (primarily to lungs), except for "SCARE" (Synovial, Clear cell, Angiosarcoma, Rhabdomyosarcoma, Epithelioid), which frequently spread via lymphatics. * **Investigation of Choice:** MRI is preferred for extremities; CT is preferred for retroperitoneal tumors. Diagnosis is confirmed via **Core Needle Biopsy**.

Question 1

Which of the following is a spindle cell tumor?

Accepted Answer

Alveolar soft tissue sarcoma

Answer

Leiomyoma

Answer

Schwannoma

Answer

Fibrous histiocytoma

Question 2

A 25-year-old male patient presents with a bony expansile swelling of the right body of the mandible and mild paresthesia of the right inferior alveolar nerve. An OPG shows a multilocular radiolucency without root resorption. A dirty white aspirate with a protein estimation of < 4 gm% is suggestive of which of the following conditions?

Accepted Answer

Odontogenic keratocyst

Answer

Ossifying fibroma

Answer

Dentigerous cyst

Answer

Mucoepidermoid carcinoma

Question 3

Needle-shaped crystals that are negatively birefringent on polarized microscopy are characteristic of which crystal-associated arthropathy?

Accepted Answer

Gout

Answer

CPPD (Calcium Pyrophosphate Dihydrate deposition disease)

Answer

Neuropathic arthropathy

Answer

Hemophilic arthropathy

Question 4

An 88-year-old woman with a history of osteoporosis presents after a fall with pain and deformity in her left wrist, lower back tenderness, and a left lower extremity that is shortened and externally rotated. Radiographs reveal a distal radius fracture, a T12 vertebral compression fracture, and a left femur fracture. What is the basic abnormality affecting this patient's bones?

Accepted Answer

Reduction in bone mass with normal bone mineralization

Answer

Abnormal collagen synthesis and failure of crosslinking

Answer

Abnormal collagen synthesis with normal crosslinking

Answer

Reduction in bone formation with defective bone mineralization

Question 5

What is the most common soft tissue tumor in adults?

Accepted Answer

Liposarcoma

Answer

Embryonal rhabdomyosarcoma

Answer

Synovial sarcoma

Answer

Malignant fibrous histiocytoma

Question 6

All are seen in Klinefelter syndrome, except?

Accepted Answer

Low FSH level

Answer

Mental retardation

Answer

Male phenotype

Answer

Azoospermia

Question 7

Dental anomaly of teeth associated with defective bone formation is seen in which of the following conditions?

Accepted Answer

Dentinogenesis imperfecta

Answer

Amelogenesis imperfecta

Answer

Odontodysplasia

Answer

Osteitis deformans

Question 8

Which are the three most common cancers that metastasize to bone?

Accepted Answer

Breast, Prostate, Lung

Answer

Kidney, Thyroid, Breast

Answer

Thyroid, Prostate, Lung

Answer

Kidney, Prostate, Lung

Question 9

A 55-year-old man, who is on dialysis due to end-stage renal disease, complains of pain in his jaw and left arm for 6 months. An X-ray of the left arm reveals multiple, small bone cysts and pathologic fractures. What is the appropriate diagnosis for this patient's bone lesions?

Accepted Answer

Osteitis fibrosa cystica

Answer

Chronic osteomyelitis

Answer

Marble bone disease

Answer

Osteoid osteoma

Question 10

Which of the following is a disorder associated with the calcium channel ryanodine receptor?

Accepted Answer

Malignant hyperthermia

Answer

Duchene Muscular Dystrophy

Answer

Tibial muscular dystrophy

Answer

Limb girdle muscle dystrophy

Bone and Soft Tissue Pathology — MCQs

Bone and Soft Tissue Pathology — MCQs

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