Bone and Soft Tissue Pathology Practice Questions

Q: Curvilinear trabeculae mimicking a Chinese character pattern are seen in which of the following conditions?

Fibrous Dysplasia. **Explanation:** **Fibrous Dysplasia** is a benign bone condition where normal bone and marrow are replaced by fibrous tissue and haphazardly arranged bony trabeculae. The characteristic histopathological hallmark is the presence of **curvilinear trabeculae** of immature (woven) bone that lack osteoblastic rimming. These shapes resemble **"Chinese characters"** or "alphabet soup." This occurs due to a mutation in the *GNAS1* gene, leading to the failure of bone-forming cells to mature. **Analysis of Incorrect Options:** * **Fibrous Cortical Defect (FCD) & Non-ossifying Fibroma (NOF):** These are histologically identical lesions characterized by a "storiform" or **whirlpool pattern** of spindle cells and hemosiderin-laden macrophages. They do not show the Chinese character trabeculae. FCD is 2cm. * **Ossifying Fibroma:** Unlike Fibrous Dysplasia, this lesion typically shows **prominent osteoblastic rimming** around the bony trabeculae and is usually localized to the craniofacial bones (mandible). **NEET-PG High-Yield Pearls:** * **Radiology:** Classic **"Ground-glass appearance"** on X-ray. * **McCune-Albright Syndrome:** Triad of Polyostotic fibrous dysplasia, Café-au-lait spots (Coast of Maine borders), and precocious puberty. * **Mazabraud Syndrome:** Fibrous dysplasia associated with soft tissue myxomas. * **Shepherd’s Crook Deformity:** A classic radiological feature involving the proximal femur.

Q: Marked reduction in the amount of dentin, widening of predentin layer, and presence of large areas of interglobular dentin are characteristic features of which condition?

Regional odontodysplasia. **Explanation:** **Regional Odontodysplasia (ROD)**, also known as **"Ghost Teeth,"** is a rare, non-hereditary developmental anomaly affecting the ectodermal and mesodermal tooth components. The characteristic histopathological features described—marked reduction in dentin volume, a widened predentin layer, and extensive areas of **interglobular dentin** (unfused calcification foci)—result from defective mineralization of the organic matrix. Radiographically, these teeth show thin enamel and dentin with enlarged pulp chambers, giving them a faint, "ghost-like" appearance. **Analysis of Incorrect Options:** * **Dentinogenesis Imperfecta:** This is a hereditary defect of dentin. While it shows thin dentin, the hallmark is the **obliteration of pulp chambers** due to continuous deposition of abnormal dentin, and it lacks the specific "ghostly" radiographic appearance of ROD. * **Amelogenesis Imperfecta:** This condition primarily affects the **enamel** (ectodermal origin). The dentin and pulp remain histologically and radiographically normal. * **Osteogenesis Imperfecta:** This is a systemic connective tissue disorder caused by Type I collagen mutations. While it is frequently associated with Dentinogenesis Imperfecta (Type I), it does not present with the localized, "regional" interglobular dentin patterns seen in ROD. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Presentation:** ROD usually affects a localized quadrant (unilateral) and often involves both primary and permanent dentition. * **Radiographic Sign:** The "Ghost Teeth" appearance is the classic buzzword. * **Etiology:** Unlike the other options, ROD is **idiopathic and non-hereditary**, often attributed to local vascular or traumatic factors during tooth development.

Q: Which bone tumor classically forms osteoid or immature bone (matrix)?

Osteosarcoma. **Explanation:** The defining characteristic of **Osteosarcoma** is the direct production of **osteoid (immature bone matrix)** by malignant mesenchymal cells. In pathology, the presence of this lace-like, eosinophilic osteoid is the "gold standard" for diagnosis. While Osteosarcoma can contain cartilage or fibrous tissue, the hallmark that distinguishes it from other bone tumors is this specific ability of the tumor cells to form bone. **Analysis of Incorrect Options:** * **B. Chondrosarcoma:** This is a malignant tumor where the cells produce a **cartilaginous matrix** (chondroid), not osteoid. It typically affects older adults and involves the axial skeleton. * **C. Fibrosarcoma:** This tumor is characterized by malignant fibroblasts producing a **collagenous/fibrous matrix**, often arranged in a "herringbone pattern." It lacks primary bone or cartilage formation. * **D. Ewing’s Sarcoma:** This is a small round blue cell tumor. It is **non-matrix producing**; it does not form bone or cartilage. It is associated with the t(11;22) translocation. **High-Yield Clinical Pearls for NEET-PG:** * **Age/Site:** Most common primary malignant bone tumor in children/adolescents; typically occurs in the **metaphysis** of long bones (distal femur > proximal tibia). * **Radiology:** Look for the **"Sunburst appearance"** (spicules of calcified bone) and **"Codman’s triangle"** (subperiosteal reactive bone formation). * **Metastasis:** Spreads primarily via the bloodstream, most commonly to the **lungs** (skip lesions may also occur). * **Associated Conditions:** Paget’s disease of bone, Li-Fraumeni syndrome (p53 mutation), and hereditary Retinoblastoma (RB1 mutation).

Q: All of the following are true about chordoma, except?

Endothelial origin. **Explanation:** **Chordoma** is a rare, slow-growing, but locally aggressive malignant bone tumor. The correct answer is **Option A** because chordomas are of **notochordal origin**, not endothelial origin. They arise from persistent remnants of the fetal notochord. * **Why Option A is the Exception:** Chordomas are ectodermal/neuroectodermal derivatives. Histologically, they are characterized by **physaliphorous cells** (large cells with bubbly, vacuolated cytoplasm) embedded in a myxoid stroma. They express epithelial markers like **Cytokeratin** and **EMA**, as well as the specific transcription factor **Brachyury**, which is a highly sensitive and specific diagnostic marker. * **Option B (More common in males):** This is a true statement. Chordomas show a slight male predilection, typically occurring in the 40–60 age group. * **Option C (Sacrococcygeal region):** This is true. The most common site is the **sacrococcygeal region (50%)**, followed by the spheno-occipital (clivus) region (35%) and the mobile spine (15%). * **Option D (Expansile lytic lesion):** This is true. Radiologically, they appear as destructive, expansile lytic lesions often associated with a large soft-tissue mass and irregular calcifications. **High-Yield Pearls for NEET-PG:** 1. **Brachyury:** The most specific diagnostic marker for chordoma. 2. **Physaliphorous cells:** The classic "soap bubble" appearance on histology. 3. **Location:** It is the most common primary malignant tumor of the sacrum. 4. **Prognosis:** Though slow-growing, they have a high rate of local recurrence after surgical excision.

Question 1

A 25-year-old man presents with right knee pain, described as "popping and catching," for the past 2 years. Examination reveals a reduced range of motion in the right knee without tenderness or swelling. MRI shows a 3-cm mass in the anterior joint space. Arthroscopic partial synovectomy is performed, and a nodular, encapsulated mass is removed. Microscopic examination of the mass reveals synoviocyte-like tumor cells in a hyalinized stroma containing osteoclast-like giant cells and hemosiderin. An antagonist to which of the following growth factors is most useful in treating this lesion?

Accepted Answer

Macrophage Colony-Stimulating Factor (M-CSF)

Answer

Epidermal Growth Factor (EGF)

Answer

Fibroblast Growth Factor (FGF)

Answer

Platelet-Derived Growth Factor (PDGF)

Question 2

Curvilinear trabeculae mimicking a Chinese character pattern are seen in which of the following conditions?

Accepted Answer

Fibrous Dysplasia

Answer

Fibrous Cortical Defect

Answer

Non-ossifying Fibroma

Answer

Ossifying Fibroma

Question 3

A patient with multiple impacted supernumerary teeth, and inability to bring his shoulders together, is suffering from which of the following conditions?

Accepted Answer

Cleidocranial dysostosis

Answer

Klinefelter's syndrome

Answer

Trisomy 21

Answer

Down's syndrome

Question 4

Marked reduction in the amount of dentin, widening of predentin layer, and presence of large areas of interglobular dentin are characteristic features of which condition?

Accepted Answer

Regional odontodysplasia

Answer

Dentinogenesis imperfecta

Answer

Amelogenesis imperfecta

Answer

Osteogenesis imperfecta

Question 5

A 50-year-old patient presents with enlarged knuckles and large subcutaneous nodules near her elbows. Her proximal interphalangeal (PIP) joints are hyperextended, and her distal interphalangeal (DIP) joints are flexed. If the nodules were biopsied, which of the following would best describe their likely histological appearance?

Accepted Answer

Fibrinoid necrosis surrounded by palisading epithelioid cells

Answer

Amorphous crystalline mass surrounded by macrophages

Answer

Cystic space caused by myxoid degeneration of connective tissue

Answer

Darkly pigmented synovium with an exuberant, villous growth

Question 6

Which bone tumor classically forms osteoid or immature bone (matrix)?

Accepted Answer

Osteosarcoma

Answer

Chondrosarcoma

Answer

Fibrosarcoma

Answer

Ewing's sarcoma

Question 7

All of the following are true about chordoma, except?

Accepted Answer

Endothelial origin

Answer

More common in males

Answer

Occurs in the sacrococcygeal region

Answer

Expansile lytic lesion

Question 8

Fish hook pattern of capillaries is seen in which of the following?

Accepted Answer

Hemangiopericytoma

Answer

Capillary hemangioma

Answer

Cavernous hemangioma

Answer

Angiosarcoma

Question 9

Which of the following are synovial sarcoma cellular markers?

Accepted Answer

Cytokeratin

Answer

S-100

Answer

Vimentin

Answer

Calretinin

Question 10

Marble bone disease, characterized by increased bone density, is due to a mutation in the gene encoding which of the following enzymes?

Accepted Answer

Carbonic anhydrase II

Answer

Carbonic anhydrase I

Answer

Carbonic anhydrase III

Answer

Carbonic anhydrase IV

Bone and Soft Tissue Pathology — MCQs

Bone and Soft Tissue Pathology — MCQs

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