Bone and Soft Tissue Pathology Practice Questions

Q: What is the most common cause of osteoblastic bone metastasis in females?

Breast cancer. **Explanation:** **1. Why Breast Cancer is Correct:** In females, **breast cancer** is the most common primary malignancy to metastasize to the bone [1]. While breast cancer often produces mixed (osteolytic and osteoblastic) lesions, it is the **most frequent cause of osteoblastic (sclerotic) metastases in women**. This occurs because tumor cells secrete factors like Bone Morphogenetic Proteins (BMPs) and TGF-β, which stimulate osteoblast proliferation and new bone formation. **2. Why Other Options are Incorrect:** * **Cervical Cancer:** While it can spread to pelvic bones, it is a much less common cause of bone metastasis compared to breast cancer and typically presents as osteolytic lesions. * **Thyroid Cancer:** Follicular thyroid carcinoma frequently metastasizes to bone [1], but these lesions are characteristically **purely osteolytic** and often "pulsatile" in nature. * **Osteosarcoma:** This is a primary bone tumor, not a metastatic process from another organ [2]. While it produces osteoid (bone), it does not fit the category of "metastasis" in this context. **3. High-Yield NEET-PG Pearls:** * **Most common cause of osteoblastic metastasis (Overall & Males):** Prostate Cancer (presents with elevated Serum Acid Phosphatase and PSA) [1]. * **Most common cause of osteolytic metastasis (Adults):** Lung Cancer and Multiple Myeloma [1]. * **Most common site for bone metastasis:** Spine (Vertebrae), followed by the femur and pelvis. * **Imaging Gold Standard:** Bone scan (Technetium-99m) is highly sensitive for osteoblastic activity, whereas PET scans or MRI are better for purely lytic lesions like Myeloma. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Osteoarticular And Connective Tissue Disease, pp. 671-674. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Osteoarticular And Connective Tissue Disease, pp. 673-674.

Q: The gene responsible for folic acid transport is situated on which chromosome?

Chromosome 21. ### Explanation **Correct Answer: D. Chromosome 21** The gene responsible for the transport of folic acid into cells is the **SLC19A1 gene** (Solute Carrier Family 19 Member 1), which encodes the **Reduced Folate Carrier (RFC-1)**. This gene is located on the long arm of **Chromosome 21 (21q22.3)**. The clinical significance of this location is particularly relevant in **Down Syndrome (Trisomy 21)**. Because patients with Down Syndrome have three copies of Chromosome 21, they have increased expression of the RFC-1 transporter. This leads to higher intracellular accumulation of methotrexate (a folate antagonist) in leukemic blasts, explaining why children with Down Syndrome and Acute Lymphoblastic Leukemia (ALL) are more sensitive to methotrexate and prone to its toxicity. **Analysis of Incorrect Options:** * **Chromosome 10:** Associated with the *PTEN* gene (Cowden syndrome) and *RET* proto-oncogene (MEN 2). It is not involved in primary folate transport. * **Chromosome 5:** Home to the *APC* gene (Familial Adenomatous Polyposis). While 5q deletions are seen in Myelodysplastic Syndrome, it does not house the primary folate transporter gene. * **X Chromosome:** Associated with conditions like Hemophilia and Duchenne Muscular Dystrophy. Folate transport deficiency (Hereditary Folate Malabsorption) is typically autosomal recessive, not X-linked. **High-Yield Clinical Pearls for NEET-PG:** * **SLC19A1/RFC-1:** Located on Chromosome 21; primary transporter for reduced folates and methotrexate. * **Down Syndrome & ALL:** Increased RFC-1 expression leads to methotrexate sensitivity. * **CBS Gene:** The Cystathionine Beta-Synthase gene is also on Chromosome 21. Its overexpression in Down Syndrome leads to decreased homocysteine levels (the opposite of homocystinuria). * **Hereditary Folate Malabsorption:** Caused by mutations in the *SLC46A1* gene (Proton-coupled folate transporter) on Chromosome 17.

Q: Peripheral giant cell granuloma occurs most commonly on which of the following locations?

Gingiva. **Explanation:** **Peripheral Giant Cell Granuloma (PGCG)** is a common reactive exophytic lesion of the oral cavity, representing a local response to chronic irritation or trauma. 1. **Why Gingiva is Correct:** The PGCG originates specifically from the **periosteum or the periodontal ligament**. Because these tissues are anatomically associated with the tooth-bearing areas, the lesion occurs exclusively on the **gingiva** (usually the interdental papilla) or the edentulous **alveolar ridge**. Between the two, the gingiva is the most frequent site of involvement. 2. **Why Other Options are Incorrect:** * **Alveolar Ridge:** While PGCG can occur here in edentulous patients, it is statistically less common than the gingival presentation in dentate individuals. * **Palate and Floor of the Mouth:** These sites lack the periodontal ligament and the specific periosteal environment required for PGCG formation. Lesions found here are more likely to be Pyogenic Granulomas or Irritation Fibromas. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Appearance:** It typically presents as a firm, reddish-blue or "liver-colored" nodule. The dark color is due to prominent vascularity and hemorrhage. * **Histopathology:** Characterized by a non-encapsulated proliferation of **multinucleated giant cells** in a background of ovoid to spindle-shaped mesenchymal cells, with prominent **hemosiderin deposits**. * **Radiology:** While "peripheral" (soft tissue), it may cause "cupping" or superficial resorption of the underlying alveolar bone. * **Differential Diagnosis:** Must be distinguished from **Central Giant Cell Granuloma (CGCG)**, which is an intraosseous lesion, and the "Brown Tumor" of hyperparathyroidism (biochemical correlation with Serum Calcium/PTH is essential).

Q: What is a common complication seen in a patient with osteopetrosis during tooth extraction?

Both jaw fracture and osteomyelitis. **Explanation:** **Osteopetrosis** (Marble Bone Disease) is a genetic disorder characterized by defective **osteoclast-mediated bone resorption**. This leads to an overgrowth of dense, sclerotic bone that is paradoxically weak and prone to complications. **Why Option C is correct:** 1. **Jaw Fracture:** Although the bones appear dense on X-ray, they lack the normal trabecular architecture and organic matrix flexibility [1]. This makes the bone extremely **brittle**. The mechanical force required for tooth extraction often exceeds the bone's threshold, leading to iatrogenic fractures. 2. **Osteomyelitis:** The excessive bone deposition encroaches upon the medullary cavity, significantly reducing the vascular supply (**avascularity**) [1]. In the jaw, where the oral cavity provides a constant source of bacteria, the lack of adequate blood flow prevents an effective immune response and healing, leading to refractory osteomyelitis following dental procedures. **Analysis of other options:** * **Option A & B:** While both are individual complications, they frequently occur concurrently or as a sequence of events in osteopetrosis patients. **High-Yield NEET-PG Pearls:** * **Pathogenesis:** Mutation in the **TCIRG1 gene** (vacuolar ATPase proton pump) or **CLCN7** (chloride channel) prevents the acidification required for bone resorption. * **Radiology:** Classic "Erlenmeyer flask deformity" of long bones and "Rugger-jersey spine" [1]. * **Hematology:** Encroachment on the marrow space leads to **pancytopenia** and extramedullary hematopoiesis (hepatosplenomegaly) [1]. * **Neurology:** Narrowing of cranial foramina can cause cranial nerve palsies (e.g., blindness or deafness) [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. 1188-1189.

Question 1

Which one of the following soft tissue sarcomas frequently metastasizes to lymph nodes?

Accepted Answer

Embryonal rhabdomyosarcoma

Answer

Fibrosarcoma

Answer

Osteosarcoma

Answer

Alveolar soft part sarcoma

Question 2

Ewing's sarcoma is associated with which marker?

Accepted Answer

CD-56

Answer

CD-38

Answer

CD-117

Answer

CD-139

Question 3

Which of the following statements is NOT TRUE about synovial sarcoma?

Accepted Answer

It is seen in individuals over 50 years of age.

Answer

It does not arise from synovium.

Answer

It occurs more commonly at extra-articular sites.

Answer

Knee and foot are common sites involved.

Question 4

What is the most common cause of osteoblastic bone metastasis in females?

Accepted Answer

Breast cancer

Answer

Cervical cancer

Answer

Thyroid cancer

Answer

Osteosarcoma

Question 5

The gene responsible for folic acid transport is situated on which chromosome?

Accepted Answer

Chromosome 21

Answer

Chromosome 10

Answer

Chromosome 5

Answer

X Chromosome

Question 6

Storiform growth pattern is seen in which of the following tumors?

Accepted Answer

All of the above

Answer

Malignant fibrous histiocytoma

Answer

Solitary fibrous tumor

Answer

Dermatofibrosarcoma protuberans

Question 7

Synovial sarcomas typically spread by which route?

Accepted Answer

Lymphatic route

Answer

Hematogenous route

Answer

Drop metastasis

Answer

It does not metastasize; it is a locally invasive tumor

Question 8

Peripheral giant cell granuloma occurs most commonly on which of the following locations?

Accepted Answer

Gingiva

Answer

Alveolar ridge

Answer

Palate

Answer

Floor of the mouth

Question 9

Narrow, high arched palate, prolonged retention of deciduous teeth, and failure in the eruption of permanent teeth are characteristic of which condition?

Accepted Answer

Cleidocranial dysplasia

Answer

Cherubism

Answer

Paget's disease

Answer

Marfan syndrome

Question 10

What is a common complication seen in a patient with osteopetrosis during tooth extraction?

Accepted Answer

Both jaw fracture and osteomyelitis

Answer

Jaw fracture

Answer

Osteomyelitis

Answer

None of the above

Bone and Soft Tissue Pathology — MCQs

Bone and Soft Tissue Pathology — MCQs

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