Bone and Soft Tissue Pathology Practice Questions

Q: Which of the following immunohistochemical markers would be expected to be positive in biopsies of Ewing's Sarcoma?

S-100. **Explanation:** **Ewing’s Sarcoma** is a highly malignant small round blue cell tumor (SRBCT) typically arising in the marrow cavity of long bones in children and young adults [2]. It is characterized by the translocation **t(11;22)(q24;q12)**, resulting in the *EWS-FLI1* fusion gene. **Why S-100 is the correct answer:** While the most sensitive and specific marker for Ewing’s Sarcoma is **CD99 (MIC2)**, approximately **10-15% of cases** can show focal positivity for **S-100**. This occurs because Ewing’s Sarcoma and Primitive Neuroectodermal Tumor (PNET) exist on a clinicopathological spectrum; S-100 positivity indicates neural differentiation within the tumor. In the context of the provided options, S-100 is the only marker associated with this lineage. **Analysis of Incorrect Options:** * **A. CD3:** A definitive marker for **T-cells**. It is used to diagnose T-cell lymphomas, not bone tumors. * **B. CD21:** A marker for **Follicular Dendritic Cells**. It is used in the diagnosis of Follicular Dendritic Cell Sarcoma. * **C. Myogenin:** A highly specific nuclear marker for **skeletal muscle differentiation**. It is the gold standard for diagnosing Rhabdomyosarcoma (another SRBCT), but it is negative in Ewing’s Sarcoma [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Most Specific Marker:** CD99 (Membranous staining). * **Genetic Hallmark:** t(11;22) involving the *EWSR1* gene. * **Radiology:** "Onion-skin" periosteal reaction. * **Histology:** Small round blue cells with scanty cytoplasm (PAS positive due to glycogen) and Homer-Wright rosettes (in PNET variants). **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] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Osteoarticular And Connective Tissue Disease, pp. 671-672.

Q: Mosaic pattern of lamellar bone histology is found in which of the following conditions?

Osteitis deformans. **Explanation:** **Osteitis deformans**, also known as **Paget’s disease of bone**, is characterized by a "mosaic pattern" of lamellar bone [1]. This pathognomonic finding occurs due to a disordered cycle of excessive bone resorption followed by disorganized bone formation [1]. The "jigsaw puzzle" appearance is created by **prominent cement lines** that join haphazardly oriented segments of lamellar bone [1]. This process results from the exhaustion of osteoblastic activity following an initial osteoclastic frenzy, leading to bone that is structurally weak despite being thick. **Analysis of Incorrect Options:** * **A. Osteopetrosis:** Characterized by "marble bone disease" where osteoclasts fail to resorb bone. Histology shows persistence of **primary spongiosa** (calcified cartilage cores) within the bone, rather than a mosaic pattern. * **B. Osteoid osteoma:** A benign bone-forming tumor characterized by a **nidus** (a central core of interlacing woven bone and osteoid) surrounded by dense sclerotic bone. * **C. Osteomalacia:** Defined by inadequate mineralization of the bone matrix. Histology shows an **increased thickness of osteoid seams** (unmineralized bone) coating the trabeculae. **High-Yield NEET-PG Pearls:** * **Stages of Paget’s:** 1. Osteolytic stage (inc. Osteoclasts) → 2. Mixed stage → 3. Osteosclerotic stage (burnt-out) [1]. * **Markers:** Elevated **Serum Alkaline Phosphatase (ALP)** with normal Calcium and Phosphorus levels. * **Radiology:** Look for "Picture frame vertebrae" or "Cotton wool appearance" of the skull [1]. * **Complication:** Increased risk of **Osteosarcoma** in elderly patients. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1191-1194.

Q: What is the most common lesion that simulates a cementoblastoma?

Periapical cemento-osseous dysplasia. **Explanation:** The **Cementoblastoma** is a true neoplasm of cementoblasts, characterized radiographically by a well-defined radiopaque mass attached to the root of a tooth, typically surrounded by a thin radiolucent halo. **Why Periapical Cemento-osseous Dysplasia (PCOD) is the correct answer:** PCOD is the most common lesion that mimics cementoblastoma because, in its **mature (late) stage**, it presents as a dense radiopaque mass located at the apex of a tooth. While PCOD is a reactive/dysplastic process rather than a neoplasm, its radiographic appearance—a dense opacity often surrounded by a radiolucent rim—closely resembles cementoblastoma. The key clinical differentiator is that in PCOD, the tooth remains **vital**, and the lesion is not physically fused to the root, unlike cementoblastoma. **Analysis of Incorrect Options:** * **Periapical Sclerosing Osteitis (Condensing Osteitis):** This is a reaction to low-grade chronic inflammation (pulpitis). While radiopaque, it lacks the characteristic radiolucent rim seen in cementoblastoma and PCOD. * **Dense Bone Island (Idiopathic Osteosclerosis):** This is a localized growth of compact bone. It is not associated with an inflammatory trigger and typically lacks a radiolucent capsule. * **Hypercementosis:** This is the non-neoplastic deposition of excessive cementum. While it involves the root, it usually results in a smooth, club-shaped enlargement of the root rather than a distinct, large globular mass. **NEET-PG High-Yield Pearls:** * **Cementoblastoma:** Always attached to the root; causes root resorption; usually involves the **mandibular first molar**. * **PCOD:** Most common in **middle-aged African/Asian females**; typically involves **mandibular anterior teeth**; teeth are always **vital**. * **Key Radiographic Sign:** The "radiolucent rim" is a hallmark for both Cementoblastoma and mature PCOD.

Q: Secondaries of which of the following cause osteolytic lesions except?

Prostate. **Explanation:** The majority of bone metastases are **osteolytic**, meaning they destroy bone tissue by stimulating osteoclast activity. However, certain cancers stimulate osteoblasts, leading to **osteoblastic (sclerotic)** lesions. **1. Why Prostate is the Correct Answer:** Carcinoma of the **Prostate** is the classic example of a malignancy that produces **osteoblastic (sclerotic) lesions**. The tumor cells secrete factors like Bone Morphogenetic Proteins (BMPs) and Prostate-Specific Antigen (PSA) that promote bone formation rather than destruction. Therefore, it is the exception to the rule of osteolytic secondaries. **2. Analysis of Incorrect Options (Osteolytic Lesions):** * **Kidney (Renal Cell Carcinoma):** Characteristically produces purely osteolytic, "blow-out" expansile lesions. These are often highly vascular. * **Bronchus (Lung Cancer):** Primarily causes osteolytic destruction. It is a common source of bone secondaries in men. * **Thyroid:** Like the kidney, thyroid secondaries are typically osteolytic and expansile (pulsatile). **High-Yield Clinical Pearls for NEET-PG:** * **Most common source of bone secondaries:** Breast (Women), Prostate (Men). * **Purely Osteoblastic:** Prostate, Carcinoid, Medulloblastoma. * **Mixed (Lytic + Blastic):** Breast (most common mixed), Lung, Cervix. * **Purely Osteolytic:** Kidney, Thyroid, GI tract, Melanoma. * **Pulsatile Secondaries:** Classically seen in **Renal Cell Carcinoma** and **Thyroid Carcinoma**. * **Investigation of choice:** **Bone Scan** (Technetium-99m) is highly sensitive for blastic lesions but may show a "cold spot" in purely lytic lesions like Multiple Myeloma.

Q: A 3-year-old girl presents with recurrent fractures following minor trauma. A detailed family history reveals similar complaints in several other family members, and a pedigree chart has been constructed (as shown below). Which of the following is the most likely mode of inheritance for this disorder?

Autosomal dominant disorder. ***Autosomal dominant disorder*** - **Vertical transmission** through multiple generations with both males and females affected equally indicates autosomal dominant inheritance, consistent with **Osteogenesis Imperfecta Type I**. - Approximately **50% of offspring** are affected in each generation, which is characteristic of autosomal dominant disorders where one affected parent passes the mutation. *Autosomal recessive disorder* - Would require **both parents** to be carriers, typically showing **horizontal transmission** (siblings affected, not parents). - **Consanguinity** would often be present in the family history, and affected individuals would appear in the same generation rather than consecutive generations. *X-linked recessive disorder* - Would predominantly affect **males** with **maternal transmission** pattern (affected grandfather → carrier daughter → affected grandson). - Affected females would be rare and typically have **skewed X-inactivation** or be homozygous, which doesn't match the equal sex distribution described. *X-linked dominant disorder* - Would show **male lethality** in most cases, with primarily affected females and **no male-to-male transmission**. - Affected males would typically have more severe manifestations or die in utero, contradicting the equal gender distribution observed in this pedigree.

Question 1

Which anatomical region of the jaw bones is most likely to harbor metastatic tumors?

Accepted Answer

Posterior molar region

Answer

Mandibular condyle

Answer

Anterior maxilla

Answer

Maxillary tuberosity

Question 2

Punctuated lesions and floating teeth are seen in which of the following conditions?

Accepted Answer

Osteitis fibrosa

Answer

Metastasis

Answer

Histiocytosis

Answer

Asbestosis

Question 3

Which of the following immunohistochemical markers would be expected to be positive in biopsies of Ewing's Sarcoma?

Accepted Answer

S-100

Answer

CD3

Answer

CD21

Answer

Myogenin

Question 4

Which condition is characterized by the absence of dystrophin?

Accepted Answer

Duchenne Muscular Dystrophy (DMD)

Answer

Myotonic Dystrophy

Answer

Becker Muscular Dystrophy

Answer

Myasthenia Gravis

Question 5

Mosaic pattern of lamellar bone histology is found in which of the following conditions?

Accepted Answer

Osteitis deformans

Answer

Osteopetrosis

Answer

Osteoid osteoma

Answer

Osteomalacia

Question 6

Adamantinoma usually arises from?

Accepted Answer

Odontogenic epithelium

Answer

Dental lamina

Answer

Endodermal tissue

Answer

Periapical tissue

Question 7

What is the most common lesion that simulates a cementoblastoma?

Accepted Answer

Periapical cemento-osseous dysplasia

Answer

Periapical sclerosing osteitis

Answer

Dense bone island

Answer

Hypercementosis

Question 8

Secondaries of which of the following cause osteolytic lesions except?

Accepted Answer

Prostate

Answer

Kidney

Answer

Bronchus

Answer

Thyroid

Question 9

A 3-year-old girl presents with recurrent fractures following minor trauma. A detailed family history reveals similar complaints in several other family members, and a pedigree chart has been constructed (as shown below). Which of the following is the most likely mode of inheritance for this disorder?

Accepted Answer

Autosomal dominant disorder

Answer

Autosomal recessive disorder

Answer

X-linked recessive disorder

Answer

X-linked dominant disorder

Question 10

In bone infarcts, all are true except?

Accepted Answer

Bone infarcts occur in thalassaemia major.

Answer

Dysbaric osteonecrosis is commonly juxta-articular.

Answer

Bone infarcts occur in Gaucher's disease.

Answer

Bone infarcts are often diaphyseal in sickle cell disease.

Bone and Soft Tissue Pathology — MCQs

Bone and Soft Tissue Pathology — MCQs

On this page

Practice by Chapter

Want unlimited practice?