Bone and Soft Tissue Pathology Practice Questions

Q: Lipoma most commonly becomes malignant at which site?

Retroperitoneal. The correct answer is **Retroperitoneal**. **1. Why Retroperitoneal is correct:** While lipomas are the most common mesenchymal tumors, they are almost always benign [1]. However, the risk of malignancy (transformation into or being misdiagnosed as **Liposarcoma**) is significantly higher in deep-seated locations. Retroperitoneal "lipomatous" masses are notoriously aggressive [1]. In fact, most experts suggest that any large, deep-seated lipomatous tumor in the retroperitoneum should be considered a **Well-Differentiated Liposarcoma (WDL)** [1]. These tumors often harbor MDM2 gene amplifications, which are absent in benign subcutaneous lipomas [1]. **2. Why the other options are incorrect:** * **Subcutaneous (Option A):** This is the most common site for lipomas (e.g., on the back, neck, or proximal extremities) [1]. These are almost universally benign and have a negligible risk of malignant transformation. * **Subaponeurotic (Option B) & Intermuscular (Option C):** These are types of "Deep Lipomas." While they are deeper than subcutaneous ones, they are still predominantly benign. **3. Clinical Pearls for NEET-PG:** * **Most common soft tissue tumor in adults:** Lipoma [1]. * **Most common soft tissue sarcoma in adults:** Liposarcoma. * **Cytogenetics:** Liposarcomas (WDL/ALT) are associated with **MDM2 and CDK4 amplification** on chromosome 12q13-15 [1]. * **Histology:** The presence of **lipoblasts** (cells with indented nuclei by lipid vacuoles) is a hallmark of liposarcoma, though not always required for the diagnosis of the well-differentiated subtype [1]. * **Rule of Thumb:** A lipomatous mass >10 cm in the retroperitoneum is a Liposarcoma until proven otherwise. **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.

Q: Articular cartilage is made up of-

Type II collagen. **Explanation:** Articular cartilage is a specialized form of **hyaline cartilage** that covers the ends of bones in synovial joints [1]. Its primary function is to provide a smooth, lubricated surface for low-friction articulation and to facilitate the transmission of loads to the underlying bone. **Why Type II Collagen is Correct:** The extracellular matrix of hyaline cartilage is unique. Approximately 90-95% of the collagen found in articular cartilage is **Type II collagen** [1]. These fibers form a dense, cross-linked network that provides tensile strength and anchors the proteoglycan aggregates (like aggrecan), which are essential for the cartilage's shock-absorbing properties. **Analysis of Incorrect Options:** * **Type I Collagen:** Found in "tough" tissues like **bone**, skin, tendons, and ligaments. It is also the primary collagen in **fibrocartilage** (e.g., intervertebral discs, pubic symphysis). * **Type III Collagen:** Known as **reticulin** fibers. It is prevalent in distensible organs like blood vessels, the uterus, and during the early stages of wound healing (granulation tissue). * **Type IV Collagen:** A non-fibrillar collagen that forms the structural framework of the **basement membrane**. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic:** "Type **Two** is for Car-ti-lage" (Two syllables for Type II). * **Osteoarthritis:** Characterized by the degradation of Type II collagen and proteoglycans, leading to joint space narrowing [1]. * **Relapsing Polychondritis:** An autoimmune condition where antibodies are directed specifically against Type II collagen. * **Water Content:** Articular cartilage is composed of nearly 70-80% water, which is vital for its load-bearing capacity [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. 1209-1210.

Question 1

A 30-year-old man presents with a radiolucent lesion. Imaging reveals a hollow cavity without epithelial lining. What is the most probable diagnosis?

Accepted Answer

Hemorrhagic bone cyst

Answer

Aneurysmal bone cyst

Answer

Static bone cavity

Answer

Ameloblastoma

Question 2

Lipoma most commonly becomes malignant at which site?

Accepted Answer

Retroperitoneal

Answer

Subcutaneous

Answer

Subaponeurotic

Answer

Intermuscular

Question 3

Tennis racquet cells are characteristic of which of the following tumors?

Accepted Answer

Rhabdomyosarcoma

Answer

Rhabdomyoma

Answer

Histiocytoma

Answer

Eosinophilic granuloma

Question 4

A 40-year-old woman has severe, disabling rheumatoid arthritis. Rheumatoid factor is positive. What would a biopsy of the synovium of her knee most likely reveal?

Accepted Answer

A proliferative synovitis with many lymphocytes, macrophages, and plasma cells

Answer

A nearly normal synovium with scattered inflammatory cells

Answer

A non-proliferative synovitis with abscess formation

Answer

A non-proliferative synovitis with many neutrophils

Question 5

The prognosis of rhabdomyosarcoma is likely to be poor if the site of the tumour is:

Accepted Answer

Extremity

Answer

Orbit

Answer

Paratesticular

Answer

Urinary bladder

Question 6

Which of the following is an example of X-linked muscular dystrophy?

Accepted Answer

Duchenne muscular dystrophy

Answer

Myotonic dystrophy

Answer

Spinal muscular atrophy

Answer

Neurogenic muscular atrophy

Question 7

Which of the following has a propensity to metastasize through lymph nodes?

Accepted Answer

Alveolar rhabdomyosarcoma

Answer

Osteosarcoma

Answer

Both

Answer

None

Question 8

Which of the following is a complication of rheumatoid arthritis of the mandibular condyle?

Accepted Answer

Fibrous ankylosis

Answer

Subluxation

Answer

Dislocation

Answer

None of the above

Question 9

In Osteomalacia, which of the following is defective?

Accepted Answer

Mineralization of bone

Answer

Osteoid formation

Answer

Both osteoid formation and mineralization of bone

Answer

None of the above

Question 10

Articular cartilage is made up of-

Accepted Answer

Type II collagen

Answer

Type I collagen

Answer

Type III collagen

Answer

Type IV collagen

Bone and Soft Tissue Pathology — MCQs

Bone and Soft Tissue Pathology — MCQs

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