Bone and Soft Tissue Pathology Practice Questions

Q: Genetic studies of a patient are positive for products of the MIC2 gene. What condition may the patient have?

Ewing's sarcoma. **Explanation:** **1. Why Ewing’s Sarcoma is Correct:** The **MIC2 gene** encodes a cell surface glycoprotein known as **CD99** (also called p30/32mic2). CD99 is a highly sensitive diagnostic marker for the **Ewing Sarcoma Family of Tumors (ESFT)**. In these patients, immunohistochemical staining shows a characteristic diffuse, strong membranous positivity for CD99. Genetically, Ewing’s sarcoma is most commonly associated with the **t(11;22)(q24;q12)** translocation, which results in the **EWS-FLI1** fusion gene. **2. Why the Other Options are Incorrect:** * **Osteosarcoma:** This is the most common primary malignant bone tumor. It is associated with mutations in **RB1** and **TP53** (Li-Fraumeni syndrome) rather than MIC2. Histologically, it is characterized by the production of malignant osteoid. [1] * **Dermatofibrosarcoma Protuberans (DFSP):** This is a soft tissue tumor characterized by a "storiform" growth pattern. Its genetic hallmark is the **t(17;22)** translocation, leading to the **COL1A1-PDGFB** fusion gene. * **Alveolar Soft Part Sarcoma:** This rare tumor is characterized by a **t(X;17)** translocation, resulting in the **ASPSCR1-TFE3** fusion gene. It typically presents in the deep soft tissues of the lower extremities in young adults. **3. High-Yield Clinical Pearls for NEET-PG:** * **Radiology:** Ewing’s sarcoma typically presents with an **"onion-skin"** periosteal reaction on X-ray. * **Morphology:** It is a member of the **"Small Round Blue Cell Tumors"** group. * **Homer-Wright Rosettes:** These may be seen in cases with neuroectodermal differentiation (PNET). * **PAS Positivity:** The tumor cells often contain glycogen, making them **PAS positive** (diastase sensitive). **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Osteoarticular And Connective Tissue Disease, pp. 671-672.

Q: What is the characteristic cytogenetic abnormality found in synovial cell sarcoma?

t(X;18). ### Explanation **Correct Option: A. t(X;18)** Synovial sarcoma is characterized by a highly specific reciprocal translocation, **t(X;18)(p11.2;q11.2)**, which is present in over 90% of cases [1]. This translocation results in the fusion of the *SS18* (formerly *SYT*) gene on chromosome 18 with one of the *SSX* genes (*SSX1*, *SSX2*, or *SSX4*) on the X chromosome [1]. The resulting fusion protein acts as an aberrant transcriptional regulator, driving oncogenesis. Despite its name, synovial sarcoma does not arise from synovial cells but from mesenchymal stem cells [1]. **Analysis of Incorrect Options:** * **B. t(17;9):** This is not a standard translocation for common soft tissue tumors. However, *t(17;22)* is characteristic of Dermatofibrosarcoma Protuberans (DFSP). * **C. t(9;22):** This is the **Philadelphia chromosome**, characteristic of Chronic Myeloid Leukemia (CML). It can also be seen in Extraskeletal Myxoid Chondrosarcoma (specifically *t(9;22)(q22;q12)* involving the *EWSR1* gene). * **D. t(11;14):** This is the hallmark of **Mantle Cell Lymphoma**, leading to the overexpression of Cyclin D1. **High-Yield Clinical Pearls for NEET-PG:** * **Biphasic Pattern:** Synovial sarcoma often shows a classic biphasic morphology consisting of epithelial-like cells (forming glands) and spindle cells [1]. * **Immunohistochemistry (IHC):** It is characteristically positive for **TLE1**, Cytokeratin, and EMA. * **Location:** Most commonly occurs in the deep soft tissues of the lower extremities (near joints) in young adults (15–40 years) [1]. * **Monophasic Variant:** Can consist of spindle cells only, making IHC and cytogenetics crucial for diagnosis [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.

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.

Question 1

Differential diagnosis of hypercementosis includes all of these EXCEPT?

Accepted Answer

Cemental aplasia

Answer

Cemental dysplasia

Answer

Condensing osteitis

Answer

Focal periapical osteopetrosis

Question 2

Which of the following vascular lesions is commonly seen in Turner syndrome?

Accepted Answer

Cavernous lymphangioma

Answer

Nevus flammeus

Answer

Pyogenic granuloma

Answer

Capillary hemangioma

Question 3

Marfan's syndrome is due to a defect of?

Accepted Answer

Fibrillin

Answer

Elastin

Answer

Collagen

Answer

Lamillin

Question 4

Genetic studies of a patient are positive for products of the MIC2 gene. What condition may the patient have?

Accepted Answer

Ewing's sarcoma

Answer

Osteosarcoma

Answer

Dermatofibroma protuberans

Answer

Alveolar cell sarcoma

Question 5

What is the characteristic cytogenetic abnormality found in synovial cell sarcoma?

Accepted Answer

t(X;18)

Answer

t(17;9)

Answer

t(9;22)

Answer

t(11;14)

Question 6

Which of the following is a spindle cell tumor?

Accepted Answer

Alveolar soft tissue sarcoma

Answer

Leiomyoma

Answer

Schwannoma

Answer

Fibrous histiocytoma

Question 7

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 8

Which of the following shows the presence of cholesterol crystals?

Accepted Answer

Keratocyst

Answer

Periodontal cyst

Answer

Aneurysmal cyst

Answer

Hemorrhagic cyst

Question 9

All are seen in Klinefelter syndrome, except?

Accepted Answer

Low FSH level

Answer

Mental retardation

Answer

Male phenotype

Answer

Azoospermia

Question 10

Bifid ribs, multiple radiolucent lesions of the jaws, multiple basal cell nevi, and falx cerebri calcification are found in which condition?

Accepted Answer

Basal cell nevus syndrome

Answer

Sturge Weber syndrome

Answer

Horner syndrome

Answer

Hereditary internal polyposis

Bone and Soft Tissue Pathology — MCQs

Bone and Soft Tissue Pathology — MCQs

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