Bone and Soft Tissue Pathology Practice Questions

Q: Osteomalacia is associated with which of the following?

Increased osteoid maturation time. **Explanation:** Osteomalacia is a metabolic bone disease characterized by **defective mineralization** of the organic bone matrix (osteoid). In a healthy state, osteoblasts secrete osteoid, which undergoes a "maturation" period before being mineralized. **Why the correct answer is right:** In Osteomalacia, the mineralization process is delayed or absent due to deficiencies (commonly Vitamin D, Calcium, or Phosphate). This leads to an **increased osteoid maturation time** (the lag time between osteoid deposition and its subsequent mineralization). Because the matrix is produced but not hardened, there is a characteristic accumulation of unmineralized bone. **Analysis of incorrect options:** * **A & B (Decreased osteoid volume/surface):** These are incorrect because Osteomalacia actually shows **increased** osteoid volume and surface. Since the osteoid is not being mineralized into mature bone, it "piles up," leading to thickened osteoid seams. * **D (Increased mineral apposition rate):** The mineral apposition rate (MAR) refers to the speed at which the mineralization front moves. In Osteomalacia, mineralization is sluggish or halted, resulting in a **decreased** mineral apposition rate. **NEET-PG High-Yield Pearls:** * **Histology Gold Standard:** Presence of widened osteoid seams (increased width and volume) and a decreased calcification rate. * **Radiology:** Look for **Looser’s zones** (Pseudofractures/Milkman’s fractures), which are pathognomonic. They are typically bilateral and symmetrical, found in the femoral neck, axillary border of the scapula, and pubic rami. * **Biochemistry:** Typically shows **low/normal Calcium**, **low Phosphate**, and **elevated Alkaline Phosphatase (ALP)**. * **Rickets vs. Osteomalacia:** Rickets occurs in children (before epiphyseal closure) and affects the growth plate; Osteomalacia occurs in adults (after epiphyseal closure).

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: A 58-year-old man with a 10-year history of gout presents with nodular masses in the periarticular tissue of the proximal and distal interphalangeal joints of his right hand. Which of the following choices best describes the characteristics of these masses?

Pathognomonic lesion of chronic gout. ### Explanation The clinical presentation of nodular masses in the periarticular tissues of a patient with long-standing gout is diagnostic of **Tophaceous Gout**. [1] **1. Why Option A is Correct:** The masses described are **tophi**, which are the hallmark of chronic polyarticular gout. [1] A tophus is a large deposit of monosodium urate (MSU) crystals surrounded by an intense inflammatory granulomatous reaction (macrophages, lymphocytes, and giant cells). The presence of a tophus is considered a **pathognomonic lesion** of chronic gouty arthritis, typically appearing about 10 years or more after the initial acute attack in untreated patients. [1] **2. Why the Other Options are Incorrect:** * **Option B:** Histologically, a tophus is a **foreign-body granuloma** centered around urate crystals. In contrast, a rheumatoid nodule consists of a central area of fibrinoid necrosis surrounded by palisading macrophages. Tophi have a white color, differentiating them from rheumatoid nodules. [1] * **Option C:** MSU crystals in gout are **needle-shaped** and show **strong negative birefringence** under polarized light. [1] Weakly positive birefringence is characteristic of Calcium Pyrophosphate Deposition Disease (CPPD/Pseudogout). [2] * **Option D:** Fibrinoid necrosis is a feature of Rheumatoid nodules and certain vasculitides, not gouty tophi. **Clinical Pearls for NEET-PG:** * **Common Sites for Tophi:** Olecranon bursa, Achilles tendon, and the **helix of the ear** (classic board-style location). [1] * **Radiology:** Look for "punched-out" erosions with overhanging edges (**Martel’s sign** or G-sign). * **Polarized Microscopy:** MSU crystals appear **yellow** when parallel to the slow vibration axis (Negative birefringence). [1] * **Treatment Goal:** In tophaceous gout, the target serum uric acid level is lower than usual (**<5 mg/dL**) to facilitate the dissolution of crystals.

Question 1

Which of the following statements is false?

Accepted Answer

B

Answer

A

Answer

C

Answer

D

Question 2

What is the most likely diagnosis for CD-99 positivity?

Accepted Answer

Ewing's sarcoma

Answer

SLL

Answer

Dermatofibroma protrubens

Answer

Malignant histiocytic fibroma

Question 3

Osteomalacia is associated with which of the following?

Accepted Answer

Increased osteoid maturation time

Answer

Decreased osteoid volume

Answer

Decreased osteoid surface

Answer

Increased mineral apposition rate

Question 4

A strict vegetarian develops osteomalacia due to insufficient vitamin D intake. Which of the following changes characterizes osteomalacia in the bones?

Accepted Answer

Increased osteoid

Answer

Decreased osteoblasts

Answer

Increased osteoclast activity

Answer

Marrow fibrosis

Question 5

A 51-year-old man presents with right hip pain and diminished range of motion of the right hip for the past 3 months. Radiographs reveal a 10 x 13 cm mass involving the right ischium of the pelvis with irregular borders, extensive bony destruction, and scattered calcifications. The mass, resected grossly, has a bluish-white cut surface. Which of the following attributes is most likely to describe this mass?

Accepted Answer

Sometimes seen to arise in benign cartilaginous tumors

Answer

The most frequent primary tumor of bone

Answer

Usually seen in distal skeletal bones

Answer

More common in females

Question 6

Prognosis in a soft tissue tumour is determined by?

Accepted Answer

Grade of tumour

Answer

Bulk of the tumour

Answer

Depth of invasion

Answer

Lymph nodal involvement

Question 7

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 8

Which of the following is the most chemoresistant tumor?

Accepted Answer

Malignant fibrous histiocytoma

Answer

Synovial sarcoma

Answer

Osteosarcoma

Answer

Embryonal rhabdomyosarcoma

Question 9

A 58-year-old man with a 10-year history of gout presents with nodular masses in the periarticular tissue of the proximal and distal interphalangeal joints of his right hand. Which of the following choices best describes the characteristics of these masses?

Accepted Answer

Pathognomonic lesion of chronic gout

Answer

Histologically similar to a rheumatoid nodule

Answer

Contains weakly positively birefringent monosodium urate crystals

Answer

Associated with fibrinoid necrosis

Question 10

A 17-year-old boy fractures his left tibia in a skiing accident. One year later, an X-ray of the leg discloses reactive bone formation in the calf muscle at the site of injury. Which of the following is the most likely diagnosis?

Accepted Answer

Myositis ossificans

Answer

Fibrous dysplasia

Answer

Malignant fibrous histiocytoma

Answer

Nodular fasciitis

Bone and Soft Tissue Pathology — MCQs

Bone and Soft Tissue Pathology — MCQs

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