Bone and Soft Tissue Pathology Practice Questions

Q: Multiple dentigerous cysts are found in which of the following conditions?

Cleidocranial dysplasia. **Explanation:** **Cleidocranial Dysplasia (CCD)** is the correct answer because it is characterized by a triad of clinical features: aplastic or hypoplastic clavicles, delayed closure of cranial sutures (fontanelles), and significant dental anomalies. The dental hallmark of CCD is the presence of **multiple supernumerary teeth** that fail to erupt. These impacted teeth often lead to the formation of **multiple dentigerous cysts** (follicular cysts) within the jaw. **Analysis of Incorrect Options:** * **Gardner’s Syndrome:** While this syndrome involves dental anomalies, it is specifically associated with **multiple osteomas** of the jaw, odontomas, and impacted teeth, rather than multiple dentigerous cysts. It is primarily known for intestinal polyposis. * **Gorlin-Goltz Syndrome (Nevoid Basal Cell Carcinoma Syndrome):** This is a classic "distractor." It is associated with **multiple Odontogenic Keratocysts (OKCs)**, not dentigerous cysts [1]. This is a high-yield distinction for exams. * **Down’s Syndrome:** Patients often exhibit delayed eruption, microdontia, and missing teeth (hypodontia), but multiple dentigerous cysts are not a characteristic feature. **High-Yield Clinical Pearls for NEET-PG:** * **Cleidocranial Dysplasia:** Caused by a mutation in the **RUNX2** gene. Look for the "ability to touch shoulders in the midline" in clinical vignettes. * **Dentigerous Cyst:** The most common developmental odontogenic cyst; it attaches to the **cementoenamel junction (CEJ)** and encloses the crown of an unerupted tooth. * **Differential for Multiple Jaw Cysts:** Always distinguish between OKCs (Gorlin-Goltz) and Dentigerous cysts (Cleidocranial dysplasia). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, pp. 1157-1158.

Q: What is the characteristic translocation seen in Ewing's sarcoma?

t(11;22). ### Explanation **Correct Option: B. t(11;22)** Ewing’s sarcoma is a highly aggressive, small round blue cell tumor of the bone and soft tissue. The hallmark of this condition is a specific chromosomal translocation, **t(11;22)(q24;q12)**, which is present in approximately 90-95% of cases. This translocation results in the fusion of the **EWS gene** (on chromosome 22) with the **FLI1 gene** (on chromosome 11), a member of the ETS family of transcription factors. The resulting **EWS-FLI1 fusion protein** acts as a potent oncogenic transcription factor that drives uncontrolled cell proliferation and survival. **Analysis of Incorrect Options:** * **A. t(2;8):** This is a variant translocation associated with **Burkitt Lymphoma** (involving c-MYC and the Ig kappa light chain). The classic translocation is t(8;14) [1]. * **C. t(x;18):** This is the characteristic translocation for **Synovial Sarcoma**, resulting in the *SYT-SSX* fusion gene [2]. * **D. t(14;18):** This is the hallmark of **Follicular Lymphoma**, leading to the overexpression of the *BCL-2* anti-apoptotic protein. **High-Yield Clinical Pearls for NEET-PG:** * **Radiology:** Classically presents with an **"Onion-skin"** periosteal reaction. * **Morphology:** Characterized by sheets of **small round blue cells**; PAS-positive (due to cytoplasmic glycogen) and **Homer-Wright rosettes** (seen in 25% of cases). * **Immunohistochemistry (IHC):** Strong membranous expression of **CD99 (MIC2)** is a highly sensitive marker. * **Demographics:** Most common in the second decade of life; typically affects the diaphysis of long bones (e.g., Femur). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 324-325. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1225-1226.

Q: Which of the following is NOT a possible effect of a dentigerous cyst on surrounding tissue?

Resorption of cortex. ### Explanation A **dentigerous cyst** (follicular cyst) is the most common developmental odontogenic cyst, arising from the separation of the follicle from around the crown of an unerupted tooth. **Why Option A is the Correct Answer:** While dentigerous cysts are known for their slow, expansive growth, they typically cause **thinning and expansion** of the cortical plates rather than frank **resorption (destruction)** of the cortex. In pathology, "resorption" of the cortex usually implies an aggressive, infiltrative, or malignant process (like Squamous Cell Carcinoma or certain aggressive Ameloblastomas). A dentigerous cyst pushes the bone boundaries outward due to osmotic pressure, maintaining a thin shell of bone around it. **Analysis of Incorrect Options:** * **B. Resorption of adjacent teeth:** Although the cyst originates from one unerupted tooth (usually the mandibular 3rd molar), the pressure exerted by the expanding cystic fluid can lead to the root resorption of neighboring erupted teeth. * **C. Displacement of the floor of the maxillary antrum:** Large cysts in the maxilla frequently expand superiorly, displacing the floor of the maxillary sinus (antrum) as they grow. * **D. Expansion of the outer cortical boundary:** This is a hallmark radiographic feature. The cyst causes a painless, slow-growing bony expansion that "balloons" the cortex outward. **Clinical Pearls for NEET-PG:** * **Radiographic Appearance:** Well-circumscribed, unilocular radiolucency attached to the **cemento-enamel junction (CEJ)** of an unerupted tooth. * **Most Common Site:** Mandibular third molars, followed by maxillary canines. * **Histopathology:** Lined by thin, non-keratinized stratified squamous epithelium (2–3 layers thick). * **Potential Complication:** If left untreated, the lining can undergo neoplastic transformation into **Ameloblastoma**, Squamous Cell Carcinoma, or Mucoepidermoid Carcinoma.

Q: The term 'ragged red fibers' is applied to describe the skeletal muscle fibers in which of the following conditions?

Mitochondrial myopathy. **Explanation:** **Mitochondrial Myopathy (Correct Answer)** The term **'Ragged Red Fibers' (RRF)** is a hallmark histological finding in mitochondrial myopathies (e.g., MERRF, MELAS) [1]. These fibers represent a compensatory proliferation of abnormal mitochondria in the subsarcolemmal and intermyofibrillar spaces of skeletal muscle. On **Gomori Trichrome stain**, these mitochondrial aggregates appear as irregular, reddish-purple granular deposits at the periphery of the muscle fiber, giving it a "ragged" appearance. **Analysis of Incorrect Options:** * **Myotonic Dystrophy:** Characterized by **ring fibers**, sarcoplasmic masses, and an increase in internal nuclei. It is an autosomal dominant disorder caused by CTG repeat expansions. * **Nemaline Myopathy:** Defined by the presence of **'Nemaline rods'** (Z-band material) within the sarcoplasm, visible on Gomori Trichrome stain as small blue-dark purple rods. * **Spinal Muscular Atrophy (SMA):** A neurogenic atrophy characterized by **groups of small, rounded atrophic fibers** (group atrophy) interspersed with hypertrophied fibers, resulting from the loss of lower motor neurons in the anterior horn of the spinal cord. **High-Yield Pearls for NEET-PG:** * **Stain of Choice:** Modified Gomori Trichrome is essential to visualize RRFs. * **Biochemical marker:** These fibers are often **SDH (Succinate Dehydrogenase) positive** (as SDH is nuclear-encoded) but **COX (Cytochrome c Oxidase) negative** (if the mutation affects mtDNA-encoded COX subunits). * **Clinical Triad:** Mitochondrial diseases often present with the triad of ophthalmoplegia, proximal muscle weakness, and lactic acidosis. * **MERRF:** Myoclonic Epilepsy with Ragged Red Fibers is the classic syndrome associated with this finding [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1305-1306.

Q: Which of the following statements about Becker muscular dystrophy is FALSE?

The gene involved is for myosin.. **Explanation:** The correct answer is **C** because Becker Muscular Dystrophy (BMD) is caused by a mutation in the **dystrophin gene** (located on the short arm of the X chromosome, Xp21), not the myosin gene [1]. Dystrophin is a vital structural protein that links the intracellular cytoskeleton (actin) to the extracellular matrix, stabilizing the sarcolemma during muscle contraction. * **Option A is true:** BMD follows an **X-linked recessive** inheritance pattern, primarily affecting males while females are typically asymptomatic carriers [2]. * **Option B is true:** BMD is characterized by **slowly progressive** proximal muscle weakness. Unlike Duchenne Muscular Dystrophy (DMD), patients with BMD often remain ambulatory well into their 20s or later. * **Option D is true:** DMD is more severe because it results from **frameshift mutations** leading to a near-total absence of dystrophin [1]. In contrast, BMD results from **non-frameshift (in-frame) mutations**, leading to the production of a truncated but partially functional dystrophin protein [1]. **NEET-PG High-Yield Pearls:** * **Genetic Locus:** The dystrophin gene is the largest known human gene, making it highly susceptible to spontaneous mutations. * **Clinical Sign:** Both DMD and BMD may present with **pseudohypertrophy of the calves** (fatty replacement of muscle). * **Diagnosis:** Gold standard is genetic testing; muscle biopsy shows diminished (not absent) dystrophin staining in BMD. * **Cardiac Involvement:** Dilated cardiomyopathy is a common cause of mortality in both conditions. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Peripheral Nerves and Skeletal Muscles, pp. 1244-1246. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, p. 151.

Question 1

Subperiosteal resorption and increased thickness of the skull is seen in which condition?

Accepted Answer

Hyperparathyroidism

Answer

Rickets

Answer

Osteomalacia

Answer

Thalassemia

Question 2

Multiple dentigerous cysts are found in which of the following conditions?

Accepted Answer

Cleidocranial dysplasia

Answer

Gardner's syndrome

Answer

Gorlin-Goltz syndrome

Answer

Down's syndrome

Question 3

What is the characteristic translocation seen in Ewing's sarcoma?

Accepted Answer

t(11;22)

Answer

t(2;8)

Answer

t(x;18)

Answer

t(14;18)

Question 4

Which of the following is NOT a possible effect of a dentigerous cyst on surrounding tissue?

Accepted Answer

Resorption of cortex

Answer

Resorption of adjacent teeth

Answer

Displacement of the floor of the maxillary antrum

Answer

Expansion of the outer cortical boundary of the involved jaw

Question 5

A 75-year-old man complains of lower back pain for years. As part of an investigation for persistently elevated lymphocytosis, a right posterior iliac crest biopsy was performed. Hematopoiesis is normal, but the bone spicules are thickened with irregular cement lines forming a mosaic appearance with both increased osteoblastic and osteoclastic activity. Which of the following conditions is most likely to occur in conjunction with this disease process?

Accepted Answer

Congestive Cardiac Failure

Answer

Dementia

Answer

Myelofibrosis

Answer

Hepatic cirrhosis

Question 6

A 60-year-old man, treated for lung cancer, presents with a rash on his chest and pain in his upper arms and calves. He has difficulty raising his arms and climbing stairs. Muscle biopsy reveals perivascular infiltrates of lymphocytes and plasma cells extending between muscle fibers. Immunofluorescence shows immune complexes in the walls of intramuscular blood vessels. What is the most likely diagnosis?

Accepted Answer

Dermatomyositis

Answer

Becker muscular dystrophy

Answer

Lambert-Eaton myasthenic syndrome

Answer

Myasthenia gravis

Question 7

Which is the most aggressive variant of ameloblastoma?

Accepted Answer

Granular cell type

Answer

Follicular type

Answer

Plexiform type

Answer

Acanthomatous type

Question 8

A 2-year-old child has a history of multiple bone fractures with minor trauma. On examination, he has hepatosplenomegaly and palsies involving cranial nerves II, VII, and VIII. Laboratory studies show pancytopenia. Radiographs reveal diffusely and symmetrically sclerotic bones with poorly formed metaphyses. Molecular analysis of his bone reveals a defect in the production of carbonic anhydrase to solubilize hydroxyapatite crystal. He is treated with hematopoietic stem cell transplantation. Which of the following cells in his bones was most likely functionally deficient and replaced following transplantation?

Accepted Answer

Osteoclast

Answer

Chondroblast

Answer

Chondrocyte

Answer

Osteoblast

Question 9

The term 'ragged red fibers' is applied to describe the skeletal muscle fibers in which of the following conditions?

Accepted Answer

Mitochondrial myopathy

Answer

Myotonic dystrophy

Answer

Nemaline myopathy

Answer

Spinal muscular atrophy

Question 10

Which of the following statements about Becker muscular dystrophy is FALSE?

Accepted Answer

The gene involved is for myosin.

Answer

It is an X-linked recessive inherited disorder.

Answer

It is characterized by slowly progressive muscle weakness of the legs and pelvis.

Answer

Duchenne muscular dystrophy is much more severe than Becker muscular dystrophy.

Bone and Soft Tissue Pathology — MCQs

Bone and Soft Tissue Pathology — MCQs

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