Bone and Soft Tissue Pathology — MCQs

Bone and Soft Tissue Pathology Indian Medical PG Practice Questions and MCQs

Question 231: Which of the following are characteristic features of cherubism?

A. Premature exfoliation of primary teeth
B. Hypoplastic defects
C. Progressive painless symmetric swelling of cheek bones
D. Both premature exfoliation of primary teeth and progressive painless symmetric swelling of cheek bones (Correct Answer)

Explanation: **Explanation:** **Cherubism** is a rare, autosomal dominant fibro-osseous disorder caused by mutations in the **SH3BP2 gene** (Chromosome 4p16). It is characterized by the replacement of normal bone with fibrous tissue and giant cell-rich lesions, primarily affecting the mandible and maxilla. **Why the correct answer is D:** * **Progressive painless symmetric swelling (Option C):** This is the hallmark clinical feature. The bilateral involvement of the posterior mandible and maxilla creates a "chubby-cheeked" appearance. If the orbital floor is involved, the eyes appear to look upward ("eyes toward heaven"), mimicking a Renaissance cherub. * **Premature exfoliation of primary teeth (Option D):** The expanding fibro-osseous lesions within the alveolar bone interfere with tooth development. This leads to the early loss (exfoliation) of primary teeth and the failure of permanent teeth to erupt (impaction). **Why other options are incorrect:** * **Option B (Hypoplastic defects):** While dental anomalies like displacement and agenesis are common, generalized enamel hypoplasia is not a defining characteristic of cherubism; the primary issue is the mechanical disruption of the dentition by the bony lesions. **NEET-PG High-Yield Pearls:** * **Genetics:** Autosomal Dominant; **SH3BP2 gene** mutation. * **Radiology:** Characterized by **bilateral, multilocular radiolucencies** (soap-bubble appearance) at the angles of the mandible. * **Histology:** Indistinguishable from **Giant Cell Granuloma** (contains multinucleated giant cells in a fibrous stroma), but distinguished clinically by its bilateral symmetry. * **Prognosis:** The condition typically manifests in early childhood (2–5 years), progresses until puberty, and then undergoes **spontaneous regression** or stabilization. Surgery is usually deferred until after puberty.

Question 232: Malignant tumour of skeletal muscle is

A. Rhabdomyoma
B. Rhabdomyosarcoma (Correct Answer)
C. Leiomyoma
D. Leiomyosarcoma

Explanation: ### Explanation **1. Why Rhabdomyosarcoma is correct:** In medical terminology, the prefix **"Rhabdomyo-"** refers to striated (skeletal) muscle, while the suffix **"-sarcoma"** denotes a malignant tumor of mesenchymal origin [1]. Therefore, **Rhabdomyosarcoma** is the malignant neoplasm arising from skeletal muscle lineage [2]. It is the most common soft tissue sarcoma in children and adolescents. **2. Why the other options are incorrect:** * **Rhabdomyoma (Option A):** This is a **benign** tumor of skeletal muscle [2]. While rare, it most commonly occurs in the heart (associated with Tuberous Sclerosis) or the head and neck region [2]. * **Leiomyoma (Option C):** The prefix **"Leio-"** means smooth. A leiomyoma is a **benign** tumor of smooth muscle (most commonly found in the uterus, known as "fibroids"). * **Leiomyosarcoma (Option D):** This is the **malignant** counterpart of smooth muscle (not skeletal muscle). It typically occurs in the uterus, gastrointestinal tract, or retroperitoneum in adults. **3. High-Yield Clinical Pearls for NEET-PG:** * **Subtypes of Rhabdomyosarcoma:** * **Embryonal:** Most common type (60%); often found in the head/neck or genitourinary tract of young children [1]. * **Alveolar:** Associated with specific translocations: **t(2;13)** or **t(1;13)** involving the *PAX3* or *PAX7* and *FOXO1* genes [2]. * **Pleomorphic:** Seen primarily in adults; carries a poor prognosis [1]. * **Diagnostic Marker:** The most specific immunohistochemical (IHC) markers for skeletal muscle differentiation are **Desmin, Myogenin, and MyoD1** [1]. * **Sarcoma Botryoides:** A variant of embryonal rhabdomyosarcoma that presents as a "grape-like" mass protruding from the vagina or bladder in infants [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. 1224-1225. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, p. 1222.

Question 233: Which of the following is characterized by large intracytoplasmic glycogen storage?

A. Fibrous dysplasia
B. Adamantinoma
C. Ewing's sarcoma (Correct Answer)
D. Osteoclastoma

Explanation: **Explanation:** **Ewing’s Sarcoma** is the correct answer because it is a "Small Round Blue Cell Tumor" characterized by cells with scant cytoplasm that contains abundant **glycogen**. This glycogen can be histologically demonstrated using a **Periodic Acid-Schiff (PAS) stain**, which appears positive, and is sensitive to diastase digestion. This is a crucial diagnostic feature used to differentiate it from other small round cell tumors like neuroblastoma or lymphoma. **Analysis of Incorrect Options:** * **Fibrous Dysplasia:** Characterized by a "Chinese letter" pattern of trabeculae of woven bone without osteoblastic rimming, set in a fibroblastic stroma. It does not show significant glycogen storage. * **Adamantinoma:** A rare, slow-growing tumor typically found in the tibia. It shows epithelial differentiation (nests of cells) resembling ameloblastoma of the jaw, rather than glycogen-rich round cells. * **Osteoclastoma (Giant Cell Tumor):** Characterized by a "double cell population" consisting of mononuclear stromal cells (the neoplastic component) and numerous multinucleated giant cells (osteoclast-like). **NEET-PG High-Yield Pearls:** * **Genetics:** Associated with **t(11;22)(q24;q12)** translocation, resulting in the **EWS-FLI1** fusion gene. * **Radiology:** Classically presents with an **"onion-skin"** periosteal reaction. * **Marker:** **CD99 (MIC2)** is a highly sensitive membrane marker for Ewing’s sarcoma. * **Origin:** It is believed to arise from primitive neuroectodermal cells (mesenchymal origin).

Question 234: What is the most common site of rhabdomyosarcoma?

A. Orbit (Correct Answer)
B. Nasopharynx
C. Extremities
D. Hypopharynx

Explanation: **Explanation:** **Rhabdomyosarcoma (RMS)** is the most common soft tissue sarcoma in children and adolescents. While it can arise anywhere in the body, the **Head and Neck region** is the most frequent overall site (accounting for approximately 40% of cases). Within the head and neck, the **Orbit** is the most common specific primary site. * **Why Orbit is Correct:** The orbit is the classic location for the **Embryonal** subtype of RMS. It typically presents as a rapidly progressing, painless proptosis in a child. Because it occurs in a confined space, it is often detected early, leading to a better prognosis compared to deep-seated tumors. [2] * **Why Other Options are Incorrect:** * **Nasopharynx/Hypopharynx:** These are "parameningeal" sites. While common in the head and neck, they occur less frequently than orbital involvement and carry a worse prognosis due to the risk of intracranial extension. * **Extremities:** This is the second most common general region (approx. 20%). However, it is the primary site for the **Alveolar** subtype, which is more aggressive and typically seen in older children/adolescents. [2] **High-Yield Clinical Pearls for NEET-PG:** * **Most common subtype:** Embryonal RMS (60%), often showing a "spindle cell" or "botryoid" (grape-like) appearance. * **Sarcoma Botryoides:** A variant of embryonal RMS found in hollow organs like the vagina (infants) or bladder. [1] * **Genetics:** Alveolar RMS is associated with **t(2;13)** or **t(1;13)** involving the *PAX3* or *PAX7* and *FOXO1* genes. * **Diagnostic Marker:** Positive for **Desmin, Myogenin, and MyoD1** (most specific). [2] * **Histology:** Look for "Rhabdomyoblasts" (tadpole or strap cells) with cross-striations. [2] **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Female Genital Tract, pp. 1004-1005. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1222, 1224-1225.

Question 235: Mutation in the GNAS1 gene is associated with which of the following conditions?

A. Fibrous dysplasia (Correct Answer)
B. Ossifying fibroma
C. Focal cementoosseous dysplasia
D. Periapical cementoosseous dysplasia

Explanation: **Explanation:** **Fibrous Dysplasia (FD)** is the correct answer [2]. It is a non-neoplastic bone lesion where normal bone is replaced by fibrous tissue and immature "woven" bone [2]. The underlying molecular defect is a **somatic gain-of-function mutation** in the **GNAS1 gene** (specifically on chromosome 20q13) [1], [2]. This mutation leads to the constitutive activation of the **Gsα protein**, resulting in an overproduction of intracellular cAMP [1]. This excess cAMP prevents the normal differentiation of osteoblasts, leading to the formation of disorganized, weak bone [2]. **Analysis of Incorrect Options:** * **Ossifying Fibroma:** Unlike FD, this is a true neoplasm. It is clinically and radiographically distinct, often showing a well-circumscribed border, and is not associated with GNAS1 mutations. * **Focal and Periapical Cemento-Osseous Dysplasia:** These are reactive fibro-osseous lesions related to the teeth (periapical region). They are generally considered idiopathic or related to local factors rather than systemic genetic mutations like GNAS1. **High-Yield Clinical Pearls for NEET-PG:** * **Histology:** Characterized by "Chinese letter" or "C-shaped" trabeculae of woven bone without osteoblastic rimming. * **Radiology:** Classically described as having a **"Ground-glass appearance"** with ill-defined borders. * **Clinical Variants:** [2] 1. **Monostotic:** Involves a single bone (70% of cases). 2. **Polyostotic:** Involves multiple bones. 3. **McCune-Albright Syndrome:** Polyostotic FD + Café-au-lait spots (Coast of Maine) + Precocious puberty (Endocrinopathy) [1], [2]. 4. **Mazabraud Syndrome:** Polyostotic FD + Soft tissue myxomas [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Endocrine System, pp. 1126-1127. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, p. 1208.

Question 236: Which of the following radiographic findings is associated with Paget’s disease?

A. Fibrous dysplasia
B. Paget’s disease (Correct Answer)
C. Hyperparathyroidism
D. Osteoma

Explanation: **Explanation:** **Paget’s Disease (Osteitis Deformans)** is a localized disorder of bone remodeling caused by increased osteoclastic activity followed by compensatory, disorganized osteoblastic activity [1]. This results in bone that is structurally weak, thickened, and highly vascular [1]. **Why the correct answer is right:** Radiographically, Paget’s disease presents in three phases: 1. **Lytic Phase:** Characterized by "Osteoporosis circumscripta" (well-defined radiolucent areas, typically in the skull). 2. **Mixed Phase:** Shows cortical thickening and coarsening of trabeculae. 3. **Sclerotic Phase:** Features "Ivory vertebrae" or a "Cotton wool appearance" of the skull due to dense, disorganized bone formation. The hallmark histological finding is the **Mosaic pattern** (Jigsaw puzzle appearance) of lamellar bone with prominent cement lines. **Analysis of Incorrect Options:** * **Fibrous Dysplasia:** Characterized by a **"Ground-glass appearance"** on X-ray [3]. Histologically, it shows "Chinese letter" patterns of woven bone without osteoblastic rimming [3]. * **Hyperparathyroidism:** Classically associated with **"Salt and pepper skull"** and **Brown tumors** (osteitis fibrosa cystica) due to excessive bone resorption [2]. * **Osteoma:** Presents as a dense, radiopaque, sessile mass, most commonly found in the paranasal sinuses or skull. It is associated with **Gardner Syndrome**. **NEET-PG High-Yield Pearls:** * **Marker of choice:** Serum **Alkaline Phosphatase (ALP)** is significantly elevated, while Calcium and Phosphate levels remain normal. * **Complications:** The most feared late complication is **Osteosarcoma** (seen in <1% of cases). * **Clinical Sign:** Increase in hat size or hearing loss (due to nerve compression in the skull) [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. 1192-1194. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, p. 1194. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, p. 1208.

Question 237: Carcinoma with predilection for metastasis to bones of hands and feet?

A. Prostate
B. Bronchus (Correct Answer)
C. Pelvis
D. Breast

Explanation: **Explanation:** The correct answer is **Bronchus (Lung Carcinoma)**. Metastasis to the small bones of the hands and feet (distal to the elbows and knees) is known as **acrometastasis**. While bone is a common site for secondary deposits from various cancers [2], acrometastasis is rare, accounting for only about 0.1% of all bone metastases. Among these, **Bronchogenic carcinoma** is the most common primary malignancy to metastasize to the hands (specifically the phalanges), followed by renal and colorectal cancers [1]. The proposed mechanism involves the hematogenous spread of tumor cells through the systemic circulation, bypassing the pulmonary filtration system [3]. **Analysis of Options:** * **Prostate (Option A):** While prostate cancer is the most common cause of **osteoblastic** (sclerotic) bone metastases [2], it typically involves the axial skeleton (pelvis, lumbar spine) via the Batson venous plexus. * **Pelvis (Option C):** This is a common *site* of metastasis, not a primary cancer type in this context. * **Breast (Option D):** Breast cancer frequently metastasizes to the bone (usually osteolytic or mixed) [2], but it favors the proximal skeleton, such as the ribs, spine, and femur, rather than the distal extremities. **NEET-PG High-Yield Pearls:** * **Most common primary for Acrometastasis:** Lung (Bronchus). * **Most common bone for metastasis:** Vertebrae (due to high vascularity). * **Osteoblastic Metastasis:** Prostate cancer, Carcinoid, Small cell lung cancer. * **Osteolytic Metastasis:** Kidney (RCC), Thyroid, Lung (NSCLC), Multiple Myeloma. * **Blow-out Metastasis:** Characteristically seen in Renal Cell Carcinoma and Thyroid Carcinoma. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Respiratory Tract Disease, pp. 337-338. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Osteoarticular And Connective Tissue Disease, pp. 671-672. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 724-725.

Question 238: Glomus tumors are most commonly seen in which of the following locations?

A. Liver
B. Adrenals
C. Pituitary
D. Finger (Correct Answer)

Explanation: **Explanation:** **Glomus tumors** (glomangiomas) are benign, exquisitely painful tumors arising from the modified smooth muscle cells of the **glomus body**. The glomus body is a specialized arteriovenous anastomosis involved in thermoregulation. 1. **Why the Finger is Correct:** Glomus bodies are most densely concentrated in the distal portions of the digits, particularly in the **subungual (under the nail) region** of the fingers. These tumors typically present as a small, firm, blue-red nodule. Clinically, they are characterized by a classic triad: **paroxysmal pain, localized tenderness, and sensitivity to cold.** 2. **Why Other Options are Incorrect:** * **Liver, Adrenals, and Pituitary:** These organs do not contain glomus bodies. While vascular tumors can occur in these sites (e.g., hepatic hemangiomas), glomus tumors are specifically cutaneous or subcutaneous lesions of the extremities. **High-Yield Clinical Pearls for NEET-PG:** * **Origin:** Derived from **Sucquet-Hoyer canals** (the arterial segment of the glomus body). * **Histology:** Characterized by nests of uniform, round "glomus cells" surrounding thin-walled vascular spaces. * **Immunohistochemistry (IHC):** Glomus cells are positive for **Alpha-Smooth Muscle Actin (α-SMA)** and Vimentin, reflecting their smooth muscle origin. They are negative for endothelial markers like CD31 (except in the vessel lining). * **Treatment:** Simple surgical excision is curative and provides immediate pain relief. * **Differential Diagnosis:** Must be distinguished from other painful skin tumors (mnemonic **LEND AN ARM**: Leiomyoma, Eccrine spiradenoma, Neuroma, Dermatofibroma, Angiolipoma, Neurilemmoma, **Glomus tumor**).

Question 239: Perifasicular atrophy of muscle fibres is seen in which condition?

A. Dermatomyositis (Correct Answer)
B. Steroid myopathy
C. Inclusion body myositis
D. Viral myositis

Explanation: **Explanation:** **Dermatomyositis (Correct Answer):** Perifascicular atrophy is the **pathognomonic** histological hallmark of Dermatomyositis [1]. The underlying mechanism is a **complement-mediated microangiopathy** (humoral immunity). Deposition of the membrane attack complex (C5b-9) in endomysial capillaries leads to capillary destruction and ischemia [1]. Because the muscle fibers at the periphery of the fascicle are furthest from the blood supply, they undergo atrophy and degeneration first, resulting in several rows of small, shrunken fibers at the fascicular edge [1]. **Analysis of Incorrect Options:** * **Steroid Myopathy:** Typically presents with **Type II muscle fiber atrophy**. It does not show inflammatory infiltrates or perifascicular patterns. * **Inclusion Body Myositis (IBM):** Characterized by **rimmed vacuoles** (containing amyloid-beta and tau protein) and endomysial inflammation [2]. It typically affects the distal muscles and is resistant to steroids. * **Viral Myositis:** Usually presents with acute muscle necrosis and nonspecific inflammatory changes rather than a specific fascicular pattern. **High-Yield NEET-PG Pearls:** * **Dermatomyositis:** Associated with **Gottron papules** (over knuckles), **Heliotrope rash** (periorbital), and an increased risk of **visceral malignancies** (e.g., ovarian, lung, gastric). * **Antibody Association:** **Anti-Mi-2** (highly specific for dermatomyositis) and **Anti-Jo-1** (associated with interstitial lung disease and "mechanic's hands") [1]. * **Polymyositis vs. Dermatomyositis:** Polymyositis involves **CD8+ T-cell** injury (cell-mediated) and shows **endomysial** inflammation [2], whereas Dermatomyositis involves **CD4+ T-cells/B-cells** and shows **perivascular/perifascicular** inflammation [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Peripheral Nerves and Skeletal Muscles, pp. 1240-1241. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Peripheral Nerves and Skeletal Muscles, pp. 1241-1242.

Question 240: Which lesion displays an ill-defined border?

A. Periapical cyst
B. Sclerosing osteitis (Correct Answer)
C. Soft tissue capsule
D. Multiple myeloma

Explanation: **Explanation:** In bone pathology, the definition of a lesion’s border is a critical diagnostic feature. An **ill-defined border** typically indicates an inflammatory process or an aggressive malignancy where the bone does not have sufficient time to form a reactive cortical rim. **1. Why Sclerosing Osteitis is correct:** Sclerosing osteitis (also known as Condensing Osteitis) is a periapical inflammatory reaction to low-grade pulpitis. It results in a localized increase in bone density (sclerosis). Because it is a reactive, inflammatory process rather than a true neoplasm, the transition between the sclerotic bone and the normal surrounding trabecular bone is gradual and diffuse, leading to an **ill-defined, non-corticated border.** [1] **2. Why the other options are incorrect:** * **Periapical Cyst:** These are typically well-defined, radiolucent lesions with a distinct, often corticated (white line) border, as they grow slowly and allow the bone to remodel. * **Soft Tissue Capsule:** By definition, a capsule provides a clear, sharp anatomical boundary between a lesion and the surrounding tissue, making it well-defined. * **Multiple Myeloma:** Classically presents as **"punched-out"** lytic lesions. These have very sharp, well-defined borders with no reactive sclerosis, making them appear as if a hole was cleanly punched through the bone. **NEET-PG High-Yield Pearls:** * **Well-defined borders:** Suggest slow-growing, benign lesions (e.g., Ameloblastoma, Odontogenic Keratocyst). * **Ill-defined/Permeative borders:** Suggest aggressive processes like Osteosarcoma, Ewing’s Sarcoma, or acute Osteomyelitis. [1] * **Sclerosing Osteitis** is most commonly associated with the mandibular first molar in young adults. Unlike an Enostosis (Idiopathic Osteosclerosis), it is always associated with a non-vital or pulpally involved tooth. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1197-1198.

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Bone Development and Growth

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Fracture Healing

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Osteomyelitis and Infectious Diseases

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Metabolic Bone Diseases

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Bone Tumors and Tumor-like Lesions

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Joints and Rheumatologic Diseases

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Soft Tissue Tumors

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Muscular Dystrophies and Myopathies

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Diseases of Tendons and Fascia

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Pathology of Orthopedic Implants

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