Bone and Soft Tissue Pathology Practice Questions

Q: A child presents with Ewing sarcoma. Histology shows it as one of the small round blue cell tumors. Which of the following accumulates in the cells of Ewing sarcoma?

Glycogen. **Explanation:** **Ewing Sarcoma** is a highly malignant, small round blue cell tumor (SRBCT) that typically arises in the marrow cavity of long and flat bones in children and adolescents. **1. Why Glycogen is the Correct Answer:** The hallmark histological feature of Ewing sarcoma cells is the presence of **abundant cytoplasmic glycogen**. This is a high-yield diagnostic point because it allows the tumor to be identified using a **Periodic Acid-Schiff (PAS) stain**, which stains the glycogen magenta. Furthermore, if the tissue is treated with **Diastase**, the glycogen is digested, and the PAS positivity disappears (PAS-positive, Diastase-sensitive). This helps differentiate Ewing sarcoma from other SRBCTs like neuroblastoma or lymphoma, which are typically PAS-negative. **2. Why Other Options are Incorrect:** * **Fat:** While some tumors (like liposarcomas) contain lipids, Ewing sarcoma cells are characterized by clear or vacuolated cytoplasm due to glycogen, not fat. * **Proteoglycans & Glycosaminoglycans:** These are components of the extracellular matrix, particularly in cartilaginous tumors (like chondrosarcoma) or myxoid tumors. They do not accumulate intracellularly in Ewing sarcoma. **3. High-Yield Clinical Pearls for NEET-PG:** * **Genetics:** Characterized by the **t(11;22)(q24;q12)** translocation, resulting in the **EWS-FLI1** fusion gene. * **Radiology:** Classic **"Onion-skin"** periosteal reaction. * **Immunohistochemistry (IHC):** Strong membranous expression of **CD99 (MIC2)** is a highly sensitive marker. * **Origin:** Derived from primitive neuroectodermal cells (mesenchymal stem cells). * **Homer-Wright Rosettes:** May be seen in cases with neuroectodermal differentiation (formerly called PNET).

Q: A cyst arising from the dental lamina is which of the following?

Glandular odontogenic cyst. Odontogenic cysts are classified based on their origin: either **developmental** (from remnants of the dental lamina or enamel organ) or **inflammatory** [1]. **1. Why the Correct Answer is Right:** The **Glandular Odontogenic Cyst (GOC)** is a rare, developmental cyst that arises from the **remnants of the dental lamina** (Serres' rests). It is characterized histologically by a lining of stratified squamous epithelium containing mucous cells and intraepithelial glandular structures (microcysts). It is known for its aggressive behavior and high recurrence rate, typically occurring in the anterior mandible. **2. Why the Other Options are Incorrect:** * **Radicular Cyst (Option A):** This is an **inflammatory** cyst, not developmental [1]. It arises from the epithelial rests of Malassez in the periodontal ligament following pulp necrosis and periapical inflammation. * **Paradental Cyst (Option B):** This is also an **inflammatory** cyst, typically associated with the buccal aspect of a partially erupted mandibular third molar with a history of pericoronitis. * **Eruption Cyst (Option C):** This is a developmental cyst, but it arises from the **reduced enamel epithelium** surrounding the crown of a tooth that is erupting through the gingiva. It is essentially a soft tissue analog of a dentigerous cyst. **3. High-Yield NEET-PG Pearls:** * **Most common odontogenic cyst:** Radicular cyst (Inflammatory). * **Most common developmental odontogenic cyst:** Dentigerous cyst (arises from reduced enamel epithelium). * **Odontogenic Keratocyst (OKC):** Also arises from the dental lamina; known for PTCH gene mutations and association with Gorlin-Goltz syndrome. * **GOC Histology Key:** Look for "hobnail cells" and "mucous-secreting cells" within the epithelial lining. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Head and Neck, p. 741.

Question 1

Dental anomaly of teeth associated with defective bone formation is seen in which of the following conditions?

Accepted Answer

Dentinogenesis imperfecta

Answer

Amelogenesis imperfecta

Answer

Odontodysplasia

Answer

Osteitis deformans

Question 2

Wormian bones are seen in which of the following conditions?

Accepted Answer

All the above

Answer

Hypothyroidism

Answer

Down's syndrome

Answer

Osteogenesis imperfecta

Question 3

Which are the three most common cancers that metastasize to bone?

Accepted Answer

Breast, Prostate, Lung

Answer

Kidney, Thyroid, Breast

Answer

Thyroid, Prostate, Lung

Answer

Kidney, Prostate, Lung

Question 4

What is the most common primary site for bony metastases?

Accepted Answer

Prostate

Answer

Kidney

Answer

Liver

Answer

Melanoma

Question 5

A true cyst derived from the stellate reticulum and growing in place of a tooth is known as?

Accepted Answer

Primordial cyst

Answer

Eruption cyst

Answer

Dentigerous cyst

Answer

Radicular cyst

Question 6

Osteogenesis imperfect is a defect in which of the following?

Accepted Answer

Collagen type I

Answer

Elastin

Answer

Collagen type IV

Answer

Basement membrane

Question 7

A child presents with Ewing sarcoma. Histology shows it as one of the small round blue cell tumors. Which of the following accumulates in the cells of Ewing sarcoma?

Accepted Answer

Glycogen

Answer

Fact

Answer

Proteoglycan

Answer

Glycosaminoglycan

Question 8

Which of the following lesions has definite loculations and is multilocular in nature?

Accepted Answer

Giant cell granuloma

Answer

Pindborg tumour

Answer

Chondroblastoma

Answer

Primordial cyst

Question 9

Dentinogenesis imperfecta differs from amelogenesis imperfecta in that, the former is characterized by calcification of pulp chambers and the root canals of the teeth?

Accepted Answer

Characterized by calcification of pulp chambers and the root canals of the teeth

Answer

A hereditary disturbance

Answer

The result of excessive fluoride ingestion

Answer

The result of faulty enamel matrix formation

Question 10

A cyst arising from the dental lamina is which of the following?

Accepted Answer

Glandular odontogenic cyst

Answer

Radicular cyst

Answer

Paradental cyst

Answer

Eruption cyst

Bone and Soft Tissue Pathology — MCQs

Bone and Soft Tissue Pathology — MCQs

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