Bone and Soft Tissue Pathology Practice Questions

Q: Which of the following genetic abnormalities is associated with Ewing's sarcoma?

t(11;22). ### Explanation **Correct Option: D. t(11;22)** Ewing’s sarcoma is a highly aggressive, small round blue cell tumor. The hallmark genetic abnormality, present in approximately 90–95% of cases, is the **t(11;22)(q24;q12)** translocation. This results in the fusion of the **EWS gene** (on chromosome 22) with the **FLI1 gene** (on chromosome 11). The resulting EWS-FLI1 fusion protein acts as an aberrant transcription factor that drives oncogenesis. **Analysis of Incorrect Options:** * **A. Defective gene at 11p13:** This refers to the **WT1 gene**, associated with **Wilms tumor** (often part of the WAGR syndrome). * **B. Defective gene at 13q14:** This refers to the **RB1 gene**, associated with **Retinoblastoma** and Osteosarcoma [1]. * **C. t(X;18):** This is the characteristic translocation for **Synovial Sarcoma** [2], resulting in the *SYT-SSX* fusion gene. **High-Yield Clinical Pearls for NEET-PG:** * **Origin:** Derived from neuroectodermal cells (PAS positive due to cytoplasmic glycogen). * **Radiology:** Classic **"onion-skin"** periosteal reaction. It typically affects the diaphysis of long bones (Femur is the most common site). * **Immunohistochemistry (IHC):** Strong membranous expression of **CD99 (MIC2)** is a highly sensitive marker. * **Differential Diagnosis:** Must be differentiated from other "Small Round Blue Cell Tumors" like Lymphoma (CD45+), Rhabdomyosarcoma (Desmin+), and Neuroblastoma (NSE+). * **Other Translocations:** A less common variant is t(21;22), involving the *ERG* gene. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1200-1202. [2] 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: What is the most common epicenter of a radicular cyst?

Apex of tooth involved. ### Explanation **1. Why "Apex of tooth involved" is correct:** A radicular cyst (also known as a periapical cyst) is the most common inflammatory odontogenic cyst [1]. Its pathogenesis begins with **pulpal necrosis** (usually due to dental caries or trauma). The necrotic pulp releases inflammatory mediators and toxins into the periapical tissues through the **apical foramen**. This chronic inflammation stimulates the **Rests of Malassez** (epithelial remnants of Hertwig’s epithelial root sheath in the periodontal ligament) to proliferate. As the epithelial mass grows, the central cells undergo ischemic necrosis, forming a fluid-filled cavity centered at the **root apex**. **2. Why other options are incorrect:** * **Distal and Mesial surfaces:** While a "lateral radicular cyst" can occur if an accessory canal exits the side of the root, this is statistically rare. The primary exit for necrotic debris is the apical foramen. * **Deep periodontal pocket:** This is the typical site for a **lateral periodontal cyst** (developmental) or a **periodontal abscess** (inflammatory), but not the classic radicular cyst. **3. High-Yield Facts for NEET-PG:** * **Most common odontogenic cyst:** Radicular cyst (~65-70% of all odontogenic cysts) [1]. * **Histopathology:** Characterized by a lining of non-keratinized stratified squamous epithelium. Look for **Rushton bodies** (eosinophilic, linear/curved calcifications) and **cholesterol clefts** with giant cells in the cyst wall. * **Radiology:** Appears as a well-defined, unilocular radiolucency at the apex of a **non-vital tooth**. * **Residual Cyst:** If the tooth is extracted but the cyst is left behind, it is termed a residual cyst. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Head and Neck, p. 741.

Q: Which of the following is the most common retroperitoneal sarcoma?

Liposarcoma. **Explanation:** **Liposarcoma** is the most common primary retroperitoneal sarcoma, accounting for approximately 30–50% of all retroperitoneal sarcomas [1]. These tumors often remain asymptomatic for long periods, growing to massive sizes before clinical detection. The most frequent histological subtypes found in the retroperitoneum are **well-differentiated** and **dedifferentiated** liposarcomas [1]. **Analysis of Options:** * **Option A (Liposarcoma):** Correct. It is the most common soft tissue sarcoma of the retroperitoneum [1]. It typically presents in the 5th to 7th decades of life. * **Option B (Leiomyosarcoma):** This is the second most common retroperitoneal sarcoma. It often arises from the walls of large veins (like the Inferior Vena Cava) or small vessels. * **Option C (Fibrosarcoma):** Once commonly diagnosed, it is now a rare diagnosis due to better immunohistochemical classification. It is more common in the deep tissues of the extremities. * **Option D (Neural sheath sarcoma):** Malignant Peripheral Nerve Sheath Tumors (MPNST) are rare in the retroperitoneum and are often associated with Neurofibromatosis Type 1 (NF1). **High-Yield NEET-PG Pearls:** * **Most common soft tissue sarcoma in adults (overall):** Liposarcoma (specifically the well-differentiated/atypical lipomatous tumor type). * **Most common soft tissue sarcoma in children:** Rhabdomyosarcoma. * **Cytogenetics:** Well-differentiated liposarcomas are characterized by the amplification of the **MDM2** gene on chromosome 12q15 [1]. * **Myxoid Liposarcoma:** Characterized by the **t(12;16)** translocation involving the *FUS-CHOP* genes [1]. * **Clinical Sign:** Retroperitoneal tumors often present with an increase in abdominal girth or a palpable mass rather than early pain. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1222-1223.

Question 1

Arnold head is a feature of which of the following conditions?

Accepted Answer

Cleidocranial dysplasia.

Answer

Fibrous dysplasia.

Answer

Paget's disease.

Answer

Cherubim.

Question 2

Which of the following genetic abnormalities is associated with Ewing's sarcoma?

Accepted Answer

t(11;22)

Answer

Defective gene at 11p13

Answer

Defective gene at 13q14

Answer

t(X;18)

Question 3

Which of the following conditions is NOT X-linked?

Accepted Answer

Facioscapulohumeral muscular dystrophy

Answer

Duchenne muscular dystrophy

Answer

Emery-Dreifuss muscular dystrophy

Answer

Becker muscular dystrophy

Question 4

Multiple osteomas, multiple polyposis, and supernumerary teeth are found in which syndrome?

Accepted Answer

Gardner's

Answer

Reiter's

Answer

Peutz-Jeghers

Answer

Behcet's

Question 5

Which of the following is the most accepted theory?

Accepted Answer

Chemioparasitic theory.

Answer

Proteolytic theory.

Answer

Proteolytic chelation theory.

Answer

Dissolution theory.

Question 6

Regarding Burkitt's lymphoma, which of the following statements is true?

Accepted Answer

CD34 negative and Surface Ig positive

Answer

CD34 positive and Surface Ig positive

Answer

CD34 positive and Surface Ig negative

Answer

CD34 negative and Surface Ig negative

Question 7

What is the most common epicenter of a radicular cyst?

Accepted Answer

Apex of tooth involved

Answer

Distal surface of tooth

Answer

Mesial surface of tooth

Answer

Deep periodontal pocket

Question 8

Which of the following statements is NOT true regarding embryonal rhabdomyosarcoma?

Accepted Answer

It is associated with prenatal exposure to Diethylstilbestrol (DES).

Answer

It is commonly seen in infants and children.

Answer

It can present as grape-like clusters, a form known as sarcoma botryoides.

Answer

Tumor cells may exhibit a tennis racket-like appearance.

Question 9

Which type of bone disease is most likely to be associated with a defect in the mineralization of adult bone secondary to abnormalities in vitamin D metabolism?

Accepted Answer

Osteomalacia

Answer

Osteogenesis imperfecta

Answer

Osteopetrosis

Answer

Osteitis fibrosa cystica

Question 10

Which of the following is the most common retroperitoneal sarcoma?

Accepted Answer

Liposarcoma

Answer

Leiomyosarcoma

Answer

Fibrosarcoma

Answer

Neural sheath sarcoma

Bone and Soft Tissue Pathology — MCQs

Bone and Soft Tissue Pathology — MCQs

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