Bone and Soft Tissue Pathology Practice Questions

Q: Which of the following is a cyst without a lining?

Hemorrhagic / Traumatic bone cyst. ### Explanation **Correct Answer: D. Hemorrhagic / Traumatic bone cyst** **Underlying Medical Concept:** In pathology, cysts are classified into **True Cysts** (lined by epithelium) and **Pseudocysts** (lacking an epithelial lining). The Hemorrhagic or Traumatic Bone Cyst (TBC) is a classic example of a **pseudocyst**. It is an empty or fluid-filled cavity within the bone that lacks a demonstrable epithelial lining. Pathogenesis is often attributed to the "Traumatic-Hemorrhage Theory," where an intramedullary clot fails to organize and instead undergoes liquefaction, leaving an empty void. **Analysis of Incorrect Options:** * **A. Radicular Cyst:** This is the most common inflammatory odontogenic cyst. It is a **true cyst** lined by non-keratinized stratified squamous epithelium, usually arising from the Rest Cells of Malassez. * **B. Dentigerous Cyst:** A developmental odontogenic cyst that surrounds the crown of an unerupted tooth. It is a **true cyst** lined by reduced enamel epithelium. * **C. Nasopalatine Duct Cyst:** The most common non-odontogenic cyst of the maxilla. It is a **true cyst** lined by a variety of epithelia (squamous, cuboidal, or respiratory/ciliated columnar). **Clinical Pearls for NEET-PG:** * **Radiographic Appearance:** TBC typically presents as a well-defined radiolucency that **scallops** between the roots of teeth without causing root resorption or tooth displacement. * **Common Site:** Most frequently found in the **mandible** (symphysis or body) of young patients (10–20 years). * **Surgical Finding:** Upon surgical exploration, the cavity is often found to be **empty** (containing only air) or containing a small amount of serosanguinous fluid. * **Other Pseudocysts to Remember:** Aneurysmal Bone Cyst (ABC) and Stafne’s Bone Cavity are also pseudocysts (no epithelial lining).

Q: Ewing's sarcoma arises from which type of cells?

Neuroectodermal cells. ### Explanation **Correct Answer: C. Neuroectodermal cells** Ewing’s Sarcoma is a highly malignant primary bone tumor. Historically, its origin was debated, but modern immunohistochemistry and molecular studies have confirmed its **neuroectodermal origin**. It belongs to the **Ewing Family of Tumors (EFT)**, which includes Peripheral Primitive Neuroectodermal Tumors (PNET). These cells are derived from the neural crest. The tumor cells characteristically express **CD99 (MIC2 gene product)** on their surface and often show neural differentiation (e.g., Homer-Wright rosettes). **Why other options are incorrect:** * **A. Totipotent cells:** These are undifferentiated cells (like a zygote) capable of forming any cell type in the body. They are not the specific origin of Ewing’s. * **B. Blastemal cells:** These are primordial cells typically associated with embryonal tumors like Wilms’ tumor (nephroblastoma), not Ewing’s sarcoma. * **D. Mesodermal cells:** While most bone tumors (like Osteosarcoma) arise from mesenchymal/mesodermal lineages, Ewing’s is unique due to its neuroectodermal markers, distinguishing it from classic mesodermal bone cancers. --- ### High-Yield Clinical Pearls for NEET-PG: * **Genetics:** Associated with **t(11;22)** translocation, leading to the **EWS-FLI1** fusion gene (found in >90% of cases). * **Age & Site:** Most common in the first and second decades of life; typically involves the **diaphysis** of long bones (e.g., Femur). * **Radiology:** Characterized by a **"moth-eaten"** lytic appearance and **"onion-peel"** periosteal reaction. * **Histology:** Features **Small Round Blue Cells** that are **PAS positive** (due to cytoplasmic glycogen). * **Clinical Presentation:** Often mimics osteomyelitis (presents with pain, swelling, fever, and elevated ESR).

Q: According to a newer hypothesis, Ewing's sarcoma arises from which part of the bone?

Medullary cavity. **Explanation:** **1. Why Medullary Cavity is Correct:** Traditionally, Ewing’s sarcoma was described as a tumor of the **diaphysis** (shaft) of long bones. However, modern pathological and radiological hypotheses emphasize that the tumor originates within the **medullary cavity** (bone marrow space). It arises from primitive neuroectodermal cells or mesenchymal stem cells located in the marrow. As the tumor grows, it permeates the Haversian canals to reach the subperiosteal space, creating the characteristic "onion-skin" periosteal reaction. **2. Why Other Options are Incorrect:** * **Diaphysis (Option B):** While this is the most common *location* along the longitudinal axis of the bone, it describes the anatomical region rather than the specific tissue of origin. Newer hypotheses focus on the intramedullary start of the lesion. * **Epiphysis (Option A):** This is the site for tumors like Giant Cell Tumor (GCT) or Chondroblastoma. Ewing’s sarcoma rarely involves the epiphysis primarily. * **Cortex (Option D):** Primary cortical tumors are rare (e.g., Osteoid Osteoma). Ewing’s sarcoma involves the cortex secondarily via destruction and permeation from the medulla. **3. Clinical Pearls for NEET-PG:** * **Genetics:** Associated with **t(11;22)** translocation involving the **EWS-FLI1** gene. * **Radiology:** Characterized by a **"moth-eaten"** appearance and **"onion-peel"** periosteal reaction. * **Histology:** Shows **Small Round Blue Cells**; PAS positive (due to glycogen) and **CD99 (MIC2)** positive. * **Clinical Presentation:** Often mimics osteomyelitis (fever, raised ESR, local pain). * **Most common site:** Femur (overall), but it is the most common tumor of the **flat bones** (pelvis) in children.

Q: Which of the following is a true neoplasm of functional cementoblasts?

Benign cementoblastoma. **Explanation:** The correct answer is **Benign Cementoblastoma**. This condition is classified as the only **true neoplasm** of cementoblasts. It is a rare, odontogenic tumor characterized by the proliferation of functional cementoblasts that form a mass of cementum-like tissue attached directly to the root of a tooth. **Why the other options are incorrect:** * **Periapical Cemental Dysplasia (PCD):** This is a **reactive/dysplastic** process, not a neoplasm. It typically occurs at the apex of vital mandibular anterior teeth and progresses through osteolytic, cementoblastic, and mature stages. * **Familial Cemental Dysplasia:** Also known as Gigantiform Cementoma, this is a hereditary **dysplastic** condition involving multiple quadrants of the jaws. While aggressive, it is considered a developmental/dysplastic anomaly rather than a true neoplasm. * **Hypercementosis:** This is a **non-neoplastic** deposition of excessive cementum on the roots of teeth. It is often associated with local factors (inflammation, trauma) or systemic conditions like Paget’s disease of bone. **High-Yield Clinical Pearls for NEET-PG:** * **Radiographic Hallmark:** Benign cementoblastoma appears as a well-defined **radiopaque mass** attached to the tooth root (usually the mandibular first molar), surrounded by a characteristic **radiolucent halo**. * **Clinical Feature:** Unlike many other odontogenic tumors, it is often associated with **localized pain and swelling**. * **Key Association:** The involved tooth remains **vital**, but the tumor is physically attached to the root, often requiring extraction of the tooth along with the lesion.

Q: The histopathology of osteopetrosis shows which of the following?

Endosteal bone formation and lack of normal bone resorption. **Explanation:** **Osteopetrosis** (also known as Marble Bone Disease or Albers-Sch$nberg disease) is a genetic disorder characterized by **defective osteoclast function or differentiation** [1]. 1. **Why Option A is correct:** The fundamental pathology is the **failure of normal bone resorption**. While osteoblasts continue to lay down bone (endosteal bone formation), the osteoclasts fail to remodel it. This results in the persistence of the primary spongiosa (calcified cartilage) within the marrow space [1]. The bone becomes symmetric, stony hard, and thickened, but paradoxically brittle. 2. **Why other options are incorrect:** * **Option B:** The pathology is primarily **endosteal** (internal remodeling) rather than periosteal (outer surface). * **Option C:** Osteopetrosis involves **increased calcification** (hypermineralization), not less. The bones are dense but lack the organized trabecular structure, making them **prone to fractures**, not resistant. * **Option D:** In most forms of osteopetrosis, osteoclasts are actually **increased in number** but are structurally dysfunctional (e.g., lacking a ruffled border) [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Erlenmeyer Flask Deformity:** Characteristic radiological finding where the ends of long bones (distal femur) are flared [1]. * **"Bone-within-bone" appearance:** Seen on X-ray due to failure of remodeling. * **Clinical Complications:** Pancytopenia (due to marrow space obliteration/myelophthisis), cranial nerve palsies (due to narrowing of neural foramina), and hepatosplenomegaly (extramedullary hematopoiesis) [1]. * **Genetic Marker:** Mutations in the **TCIRG1** gene (proton pump) or **CAII** (Carbonic Anhydrase II) are common causes. **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

Bone affection in scurvy is due to which of the following?

Accepted Answer

Defective osteoid matrix formation

Answer

Poor mineralization of the osteoid tissue

Answer

Defective calcification in osteoid

Answer

Increased degradation of osteoid tissue

Question 2

The SS18-SSX gene fusion is associated with which of the following entities?

Accepted Answer

Synovial sarcoma

Answer

Liposarcoma

Answer

Rhabdomyosarcoma

Answer

Ewing sarcoma

Question 3

Which of the following is a cyst without a lining?

Accepted Answer

Hemorrhagic / Traumatic bone cyst

Answer

Radicular cyst

Answer

Dentigerous cyst

Answer

Nasopalatine duct cyst

Question 4

Which histologic variant of rhabdomyosarcoma has the most favorable prognosis?

Accepted Answer

Embryonal

Answer

Alveolar

Answer

Mixed

Answer

Prognosis is equally poor in all variants

Question 5

Ewing's sarcoma arises from which type of cells?

Accepted Answer

Neuroectodermal cells

Answer

Totipotent cells

Answer

Blastemal cells

Answer

Mesodermal cells

Question 6

Elephantiasis neuromatosa is a feature of which of the following conditions?

Accepted Answer

Von Recklinghausen's disease

Answer

Neurilemmoma

Answer

Paraganglioma

Answer

Multiple endocrine neoplasia syndrome

Question 7

According to a newer hypothesis, Ewing's sarcoma arises from which part of the bone?

Accepted Answer

Medullary cavity

Answer

Epiphysis

Answer

Diaphysis

Answer

Cortex

Question 8

Immature bony trabeculae are found in which of the following conditions?

Accepted Answer

Fibrous dysplasia

Answer

Paget's disease

Answer

Rickets

Answer

Cleidocranial Dysplasia

Question 9

Which of the following is a true neoplasm of functional cementoblasts?

Accepted Answer

Benign cementoblastoma

Answer

Periapical cemental dysplasia

Answer

Familial cemental dysplasia

Answer

Hypercementosis

Question 10

The histopathology of osteopetrosis shows which of the following?

Accepted Answer

Endosteal bone formation and lack of normal bone resorption

Answer

Periosteal bone formation and lack of normal bone resorption

Answer

Presence of extra collagen fibers and less calcification resulting in resistance of bones to fracture

Answer

Presence of numerous osteoclasts and a few osteoclasts

Bone and Soft Tissue Pathology — MCQs

Bone and Soft Tissue Pathology — MCQs

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