Bone and Soft Tissue Pathology Practice Questions

Q: In Duchenne's muscular dystrophy, what is the state of the calf muscle?

Pseudohypertrophied. **Explanation:** In **Duchenne Muscular Dystrophy (DMD)**, the calf muscles (gastrocnemius and soleus) characteristically appear enlarged, a phenomenon known as **Pseudohypertrophy**. **Why Pseudohypertrophy is the correct answer:** DMD is an X-linked recessive disorder caused by a mutation in the **Dystrophin gene** (the largest known human gene) [1]. The absence of dystrophin leads to progressive myofiber necrosis. As muscle fibers are lost, they are replaced by an extensive proliferation of **fibro-fatty tissue** (fat and connective tissue). This replacement increases the bulk of the muscle, making it look "hypertrophied" to the naked eye, while the actual functional muscle tissue is severely diminished. **Analysis of Incorrect Options:** * **Hypertrophied:** True hypertrophy involves an increase in the size of individual muscle fibers (e.g., in athletes). In DMD, the muscle fibers are actually dying, not growing [1]. * **Atrophied:** While the muscle fibers themselves undergo atrophy and necrosis, the overall clinical appearance of the calf is one of enlargement due to fat deposition, making "atrophied" clinically inaccurate for the calf. * **Pseudoatrophied:** This is not a standard pathological term used to describe the clinical presentation of DMD. **NEET-PG High-Yield Pearls:** * **Gower’s Sign:** Patients use their hands to "climb up" their own legs to stand up due to proximal muscle weakness. * **Biochemical Marker:** Serum **Creatine Kinase (CK)** levels are massively elevated (often 10–100x normal) from birth. * **Becker Muscular Dystrophy:** A milder form where dystrophin is truncated/mutated but present (unlike DMD where it is absent) [1]. * **Cause of Death:** Usually respiratory failure or **Dilated Cardiomyopathy**. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Peripheral Nerves and Skeletal Muscles, pp. 1244-1245.

Q: Calcification of the intervertebral disc is a feature of which condition?

Alkaptonuria. **Explanation:** **Alkaptonuria** is an autosomal recessive metabolic disorder caused by a deficiency of the enzyme **homogentisate 1,2-dioxygenase**. This leads to the accumulation of homogentisic acid (HGA) in the body. HGA binds to collagen in connective tissues, a process known as **Ochronosis**. In the spine, this pigment deposition leads to the degeneration, narrowing, and subsequent **calcification of the intervertebral discs**. On X-ray, this appears as "wafer-like" calcification of multiple discs, which is a classic diagnostic hallmark. **Analysis of Incorrect Options:** * **Ankylosing Spondylitis:** Characterized by "Bamboo spine" due to marginal syndesmophytes and fusion of the sacroiliac joints, but it does not typically feature primary disc calcification. * **Hyperparathyroidism:** Associated with "Rugger-jersey spine" (subperiosteal resorption and sclerosis) and metastatic calcification in soft tissues, but not specifically isolated intervertebral disc calcification. * **Charcot’s Disease (Neuropathic Joint):** Leads to severe joint destruction, disorganized bone formation (debris), and sclerosis due to loss of sensation, but not the systematic calcification of discs. **High-Yield NEET-PG Pearls:** * **Triad of Alkaptonuria:** 1. Homogentisic aciduria (urine turns black on standing/alkalinization), 2. Ochronosis (blue-black pigmentation of cartilage/sclera), 3. Ochronotic arthritis. * **Radiology:** Look for the "wafer-like" calcification of intervertebral discs and narrowing of the joint space. * **Diagnosis:** Confirmed by detecting homogentisic acid in urine using thin-layer chromatography or the Ferric Chloride test (transient green color).

Q: Histology from a bone biopsy of the proximal femur is shown for a 50-year-old patient presenting with bone pain. What is your diagnosis?

Paget’s disease. ***Paget's disease*** - Classic histological features include a **mosaic cement-line pattern** with chaotic **woven bone** architecture replacing normal lamellar bone structure. - Presence of large **multinucleated osteoclasts** and **fibrovascular marrow replacement** are pathognomonic findings in bone biopsies. *Osteomalacia* - Histologically shows **unmineralized osteoid seams** and **delayed mineralization** with widened osteoid borders. - Characterized by **pseudofractures (Looser zones)** and absence of the mosaic pattern seen in Paget's disease. *Osteoporosis* - Shows **thinned trabecular bone** with normal **lamellar architecture** and reduced bone mass without structural abnormalities. - Lacks the **chaotic woven bone pattern** and abnormal osteoclastic activity characteristic of Paget's disease. *Osteosclerosis* - Demonstrates **increased bone density** with **thickened cortical and trabecular bone** but maintains normal lamellar structure. - Does not exhibit the **mosaic cement-line pattern** or **fibrovascular marrow changes** typical of Paget's disease.

Q: All of the following are malignant tumors except?

Fibromatosis. **Explanation:** The core of this question lies in distinguishing between benign, locally aggressive, and frankly malignant neoplasms. **1. Why Fibromatosis is the Correct Answer:** **Fibromatosis** (specifically Desmoid tumors) is classified as a **locally aggressive** fibroblastic proliferation [1]. While it lacks the metastatic potential required to be labeled "malignant," it is clinically significant because it is infiltrative, lacks a capsule, and has a high rate of local recurrence after excision [1]. In the spectrum of tumors, it sits in the "intermediate" category—locally destructive but non-metastasizing. **2. Analysis of Incorrect Options:** * **Chloroma (Granulocytic Sarcoma):** This is a solid collection of leukemic blast cells (usually AML) occurring outside the bone marrow. Despite the name ending in "-oma," it is a **malignant** extramedullary manifestation of leukemia. * **Askin’s Tumor:** This is a primitive neuroectodermal tumor (PNET) of the chest wall. It belongs to the **Ewing sarcoma family** of tumors and is highly **malignant** and aggressive. * **Liposarcoma:** This is a **malignant** tumor of adipocytes (fat cells) [1]. It is one of the most common soft tissue sarcomas in adults, typically occurring in the retroperitoneum or deep soft tissues of the extremities [1]. **High-Yield Clinical Pearls for NEET-PG:** * **The "-oma" Trap:** Not all "-omas" are benign. Classic malignant examples include Lymphoma, Melanoma, Seminoma, Mesothelioma, and Chloroma. * **Gardner Syndrome:** Deep fibromatosis (Desmoid tumors) is strongly associated with Gardner Syndrome (a variant of FAP). * **Askin's Tumor Marker:** Often shows a characteristic **t(11;22)** translocation, similar to Ewing Sarcoma. * **Chloroma Appearance:** It gets its name from the greenish color caused by the presence of the enzyme **myeloperoxidase (MPO)**.

Q: An African-American patient shows a radiolucent area surrounding the apices of mandibular anterior teeth which are vital. What is the most probable diagnosis?

Periapical cemental dysplasia. **Explanation:** The correct diagnosis is **Periapical Cemental Dysplasia (PCD)**, a subtype of Cemento-osseous dysplasia. This condition is a benign, reactive process where normal bone is replaced by fibrous tissue and cementum-like material. **Why it is correct:** 1. **Demographics:** It shows a strong predilection for **African-American females** (typically middle-aged). 2. **Location:** It characteristically involves the **mandibular anterior teeth**. 3. **Tooth Vitality:** Crucially, the involved teeth remain **vital**. This is the most important clinical differentiator from inflammatory periapical lesions. 4. **Radiographic Stages:** In its early (osteolytic) stage, it appears as a circumscribed radiolucency at the apex, mimicking an infection. **Why other options are incorrect:** * **Periapical Abscess & Granuloma:** These are inflammatory responses to pulpal necrosis. Therefore, the associated teeth would be **non-vital** (dead pulp). * **Condensing Osteitis:** This is a radiopaque (white) lesion representing a focal bony reaction to low-grade chronic infection. It is not radiolucent and involves non-vital teeth. **High-Yield Clinical Pearls for NEET-PG:** * **Management:** No treatment is required for PCD; biopsy should be avoided as it may lead to secondary osteomyelitis. * **Progression:** The lesion evolves from **Radiolucent** (Early) → **Mixed** → **Radiopaque** (Mature) with a thin radiolucent rim. * **Florid Cemento-osseous Dysplasia:** A more extensive form involving multiple quadrants of the jaw.

Question 1

In Duchenne muscular dystrophy, the defect is in the gene producing which protein?

Accepted Answer

Dystrophin

Answer

Alpha-actinin

Answer

Nebulin

Answer

Desmin

Question 2

A 47-year-old man presents with a 4-month history of dull, constant pain in the midsection of the right thigh. Physical examination reveals pain on palpation of the anterior right thigh, exacerbated by movement, and a larger circumference of the right thigh compared to the left. Radiography shows no fracture but an ill-defined soft-tissue mass anterior to the femur. MRI reveals a 10x8x7 cm solid mass deep to the quadriceps, without femur involvement. Karyotypic analysis of tumor cells shows t(12;16)(q13;p11) with amplification of the MDM2 gene. What is the most likely diagnosis?

Accepted Answer

Liposarcoma

Answer

Chondrosarcoma

Answer

Metastatic adenocarcinoma

Answer

Nodular fasciitis

Question 3

In Duchenne's muscular dystrophy, what is the state of the calf muscle?

Accepted Answer

Pseudohypertrophied

Answer

Hypertrophied

Answer

Atrophied

Answer

Pseudoatrophied

Question 4

Calcification of the intervertebral disc is a feature of which condition?

Accepted Answer

Alkaptonuria

Answer

Ankylosing spondylitis

Answer

Hyperparathyroidism

Answer

Charcot's disease

Question 5

Which of the following bone diseases characteristically exhibits a single lesion in a single bone?

Accepted Answer

Central giant cell granuloma

Answer

Osteopetrosis

Answer

Paget's disease of the bone

Answer

Polyostotic fibrous dysplasia

Question 6

Which of the following is TRUE about desmoid tumors?

Accepted Answer

Alterations in the Adenomatous Polyposis Coli (APC) / beta-catenin pathway are noted.

Answer

They consist of proliferating malignant-appearing fibroblastic cells with abundant mitoses.

Answer

Primary modality of treatment is radiotherapy.

Answer

They have a strong tendency to metastasize.

Question 7

What is the most common histological type of rhabdomyosarcoma?

Accepted Answer

Embryonal

Answer

Pleomorphic

Answer

Alveolar

Answer

Botryoid

Question 8

Histology from a bone biopsy of the proximal femur is shown for a 50-year-old patient presenting with bone pain. What is your diagnosis?

Accepted Answer

Paget’s disease

Answer

Osteomalacia

Answer

Osteoporosis

Answer

Osteosclerosis

Question 9

All of the following are malignant tumors except?

Accepted Answer

Fibromatosis

Answer

Chloroma

Answer

Askin's tumor

Answer

Liposarcoma

Question 10

An African-American patient shows a radiolucent area surrounding the apices of mandibular anterior teeth which are vital. What is the most probable diagnosis?

Accepted Answer

Periapical cemental dysplasia

Answer

Periapical abscess

Answer

Periapical granuloma

Answer

Condensing osteitis

Bone and Soft Tissue Pathology — MCQs

Bone and Soft Tissue Pathology — MCQs

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