Bone and Soft Tissue Pathology Practice Questions

Q: Which of the following statements is FALSE regarding ossifying fibroma?

Maxilla is affected more frequently than the mandible. **Explanation:** Ossifying fibroma is a benign fibro-osseous neoplasm of the jaw characterized by the replacement of normal bone with fibrous tissue containing mineralized products. **Why Option B is the Correct (False) Statement:** In ossifying fibroma, the **mandible is affected much more frequently than the maxilla** (ratio of approximately 2:1 or higher). The molar and premolar regions of the mandible are the most common sites of involvement. Therefore, the statement that the maxilla is affected more frequently is incorrect. **Analysis of Other Options:** * **Option A:** It typically affects adults in their **third and fourth decades** of life, with a significant predilection for females. * **Option C:** Radiographically, it appears as a well-demarcated, **circumscribed lesion**. Depending on the degree of calcification, it can range from radiolucent to a mixed "ground-glass" **radiopacity**. Its well-defined borders help differentiate it from fibrous dysplasia [1]. * **Option D:** Unlike fibrous dysplasia (which often stabilizes after puberty) [1], ossifying fibroma is a true neoplasm that **exhibits continuous, slow growth**, potentially causing significant bone expansion and facial asymmetry if left untreated. **NEET-PG High-Yield Pearls:** * **Differential Diagnosis:** The most important distinction is from **Fibrous Dysplasia**. Ossifying fibroma is well-circumscribed (easy to "shell out" surgically), whereas fibrous dysplasia blends into the surrounding bone (orange-peel appearance) [1]. * **Histology:** Features a cellular fibrous stroma with varying amounts of bony trabeculae or cementum-like spherules. * **Treatment:** Surgical enucleation or curettage is the treatment of choice due to its well-defined margins. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, p. 1208.

Q: What is the origin of the Pindborg tumour?

Stratum intermedium. **Explanation:** The **Pindborg tumor**, medically known as **Calcifying Epithelial Odontogenic Tumor (CEOT)**, is a rare, benign but locally aggressive odontogenic neoplasm. **Why Option B is correct:** The tumor cells in CEOT histologically resemble the cells of the **stratum intermedium** of the enamel organ. This is supported by the presence of high alkaline phosphatase activity and the characteristic polyhedral epithelial cells with prominent intercellular bridges (desmosomes) seen on histopathology. **Analysis of Incorrect Options:** * **Option A (Reduced Enamel Epithelium):** This is the origin of the **Dentigerous cyst** and is also associated with the Adenomatoid Odontogenic Tumor (AOT), but not CEOT. * **Option C (Dental Lamina):** Remnants of the dental lamina (Rests of Serres) are typically the origin of the **Odontogenic Keratocyst (OKC)** and Ameloblastoma [1]. * **Option D:** Since the origin is specifically linked to the stratum intermedium, "All of the above" is incorrect. **NEET-PG High-Yield Pearls for Pindborg Tumor:** 1. **Radiology:** Classically presents as a unilocular or multilocular radiolucency with a **"Driven Snow" appearance** (radiopaque foci due to calcification). 2. **Histopathology:** Characterized by **Liesegang rings** (concentric calcifications) and **Liesegang-like amyloid-containing areas** that stain with Congo Red and show **apple-green birefringence** under polarized light. 3. **Location:** Most commonly occurs in the **posterior mandible** (molar-ramus area) and is often associated with an impacted tooth. 4. **Nature:** It is a slow-growing, painless swelling but has a recurrence rate of about 14%. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Head and Neck, pp. 741-742.

Q: On a routine radiographic exam, a well-defined radiolucent lesion was seen in the body of the mandible of a 17-year-old boy. At the time of operation, it proved to be an empty cavity. This is a(an) ____?

Traumatic bone cyst. ### Explanation The correct answer is **Traumatic Bone Cyst (TBC)**, also known as a Simple Bone Cyst or Solitary Bone Cyst. **1. Why Traumatic Bone Cyst is Correct:** The hallmark of a Traumatic Bone Cyst is that it is a **"pseudocyst"** (lacking an epithelial lining) which, upon surgical exploration, is found to be an **empty, air-filled cavity** or contains only a small amount of serosanguinous fluid. Radiographically, it appears as a well-defined radiolucency, typically in the mandible of young patients (second decade). A classic diagnostic feature is its **scalloped border** extending between the roots of the teeth without causing root resorption or tooth displacement. **2. Why the Other Options are Incorrect:** * **A. Osteoporotic bone marrow:** This refers to focal areas of hematopoietic marrow that appear radiolucent but contain fatty or cellular marrow, not an empty cavity. * **B. Aneurysmal bone cyst (ABC):** Unlike TBC, an ABC is a reactive lesion filled with **blood-filled sinusoidal spaces**. It typically causes significant cortical expansion and "blow-out" appearances, which are absent here. * **C. Odontogenic keratocyst (OKC):** An OKC is a true cyst with a distinct **keratinized epithelial lining**. It is filled with thick, "cheesy" keratin debris, not empty space, and often shows aggressive growth. **3. High-Yield Clinical Pearls for NEET-PG:** * **Age/Site:** Most common in the 10–20 age group; predominantly involves the posterior mandible. * **Pathogenesis:** Though the exact cause is unknown, the "Hemorrhage-clot-trauma theory" suggests it results from intramedullary hemorrhage that fails to organize and instead liquefies. * **Radiology:** Look for the **"scalloping"** effect between teeth. * **Vitality:** Teeth associated with a TBC are almost always **vital**. * **Treatment:** Surgical "curettage" of the bony walls induces bleeding, which leads to clot formation and subsequent bone healing.

Q: MIC-2 is a marker of?

Ewing sarcoma. **Explanation:** **MIC-2** (also known as **CD99**) is a cell surface glycoprotein that is highly characteristic of the **Ewing Sarcoma/Primitive Neuroectodermal Tumor (PNET)** family. It is encoded by the *MIC2* gene located on the pseudoautosomal region of the X and Y chromosomes. 1. **Why Ewing Sarcoma is Correct:** In Ewing Sarcoma, MIC-2/CD99 shows a distinctive **strong, diffuse, membranous staining** pattern on immunohistochemistry (IHC). While not 100% specific, it is a highly sensitive marker used to differentiate Ewing sarcoma from other "small round blue cell tumors" of childhood. 2. **Why Other Options are Incorrect:** * **Chronic Lymphocytic Leukemia (CLL):** The hallmark markers for CLL are **CD5, CD19, CD20, and CD23**. MIC-2 is not used for its diagnosis. * **Mantle Cell Lymphoma (MCL):** MCL is characterized by the overexpression of **Cyclin D1** (due to t(11;14)) and markers like **CD5** and **SOX11** [1]. 3. **High-Yield Clinical Pearls for NEET-PG:** * **Genetics:** Ewing Sarcoma is most commonly associated with **t(11;22)(q24;q12)**, leading to the **EWS-FLI1** fusion gene. * **Radiology:** Classically presents with an **"onion-skin"** periosteal reaction. * **Morphology:** Small round blue cells with scant cytoplasm; **Homer-Wright rosettes** may be seen (indicating neural differentiation). * **Differential Diagnosis:** Other CD99-positive tumors include lymphoblastic lymphoma and synovial sarcoma, but in the context of bone tumors, it strongly points to Ewing's. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, pp. 610-612.

Q: Which of the following is described as a unicentric, non-functional, anatomically benign, and clinically persistent tumor?

Ameloblastoma. **Explanation:** The question describes the classic definition of **Ameloblastoma** as proposed by Robinson. 1. **Why Ameloblastoma is correct:** Ameloblastoma is a true neoplasm of odontogenic epithelium. It is characterized as: * **Unicentric:** It originates from a single center (though it can be multicentric in rare cases). * **Non-functional:** It does not produce hard tooth structures (enamel or dentin). * **Anatomically Benign:** Histologically, it lacks features of malignancy (like anaplasia or rapid metastasis). * **Clinically Persistent:** It is locally invasive, has a high recurrence rate, and can cause significant bone destruction, making it "locally malignant" in behavior. 2. **Analysis of Incorrect Options:** * **CEOT (Pindborg Tumor):** While it is a neoplasm, it is characterized by the production of amyloid-like material and calcifications (Liesegang rings), which differentiates its "functional" nature from Ameloblastoma. * **Enameloma (Enamel Pearl):** This is a developmental anomaly (ectopic enamel), not a true persistent neoplasm. * **Odontoma:** These are considered **hamartomas** rather than true neoplasms. They are "functional" as they produce mature enamel, dentin, and cementum. **High-Yield Clinical Pearls for NEET-PG:** * **Most common site:** Mandible (80%), specifically the molar-ramus area. * **Radiological appearance:** Classically described as a **"Soap bubble"** or **"Honeycombed"** multilocular radiolucency. * **Histopathology:** Shows "Vickers-Gorlin" features—palisading basal cells with **reverse polarity** and subnuclear vacuolization. * **Most common variant:** Follicular type. * **Unicystic Ameloblastoma:** Often associated with an impacted third molar, mimicking a dentigerous cyst.

Q: If both parents have Achondroplasia, what are their chances of having a child without Achondroplasia?

25%. **Explanation:** **1. Understanding the Correct Answer (B - 25%):** Achondroplasia is an **Autosomal Dominant (AD)** disorder caused by a gain-of-function mutation in the **FGFR3 gene** [1]. In clinical practice, almost all surviving individuals with Achondroplasia are **heterozygous (Aa)**. This is because the homozygous state (AA) is **lethal** in utero or the early neonatal period. When two heterozygous parents (Aa x Aa) conceive, the Mendelian inheritance pattern is: * **25% AA:** Homozygous dominant (Lethal/Stillborn) * **50% Aa:** Heterozygous (Affected with Achondroplasia) * **25% aa:** Homozygous recessive (**Normal stature/Without Achondroplasia**) Therefore, there is a 1 in 4 (25%) chance of having a child with a normal phenotype. **2. Why Other Options are Incorrect:** * **A (0%):** Incorrect because the parents are heterozygous; they both carry the recessive "normal" allele (a). * **C (50%):** This is the probability of having a surviving child with Achondroplasia (Aa). * **D (100%):** This would only occur if both parents were homozygous recessive (aa), which is not the case here. **3. NEET-PG High-Yield Clinical Pearls:** * **Most Common Cause:** Mutation in **FGFR3** (Fibroblast Growth Factor Receptor 3) on Chromosome 4p [1]. * **Inheritance:** 80% of cases are due to **de novo mutations**, strongly associated with **advanced paternal age** [1]. * **Key Feature:** It is the most common cause of disproportionate short stature (rhizomelic shortening) [1]. * **Radiology:** Look for "trident hand," narrowed interpedicular distance in the lumbar spine, and a "champagne glass" pelvis. * **Lethality:** Always remember that **homozygous Achondroplasia is a lethal skeletal dysplasia**, characterized by severe pulmonary hypoplasia.

Q: Which of the following carcinomas metastasizes to bone EXCEPT:

Liver. **Explanation:** The skeleton is the third most common site for metastatic disease, following the lung and liver. While many tumors can spread to bone, certain "select" carcinomas are notorious for their predilection for skeletal metastasis. **Why Liver is the Correct Answer:** Primary **Hepatocellular Carcinoma (HCC)** rarely metastasizes to the bone. It primarily spreads via intrahepatic routes or to the lungs and abdominal lymph nodes. While bone metastasis can occur in advanced stages, it is significantly less common compared to the other organs listed. Therefore, in the context of standard NEET-PG "except" questions regarding common bone-seeking tumors, the liver is the outlier. **Analysis of Incorrect Options:** * **Thyroid:** Thyroid carcinoma (especially Follicular type) is a classic "bone-seeking" tumor. These metastases are typically **osteolytic** and highly vascular (pulsatile). * **Prostate:** This is the most common cause of bone metastasis in elderly males. It is unique because it characteristically produces **osteoblastic** (sclerotic) lesions. * **Breast:** The most common cause of bone metastasis in females. These lesions are usually **mixed** (both osteolytic and osteoblastic) or purely lytic. **High-Yield NEET-PG Pearls:** * **Mnemonic for Bone Metastasis:** "**PB-KTL**" (Lead Kettle) – **P**rostate, **B**reast, **K**idney, **T**hyroid, **L**ung. * **Most common site of bone metastasis:** Spine (specifically the thoracic spine). * **Osteoblastic lesions:** Prostate (most common), Carcinoid, Small cell lung cancer. * **Osteolytic lesions:** Kidney (RCC), Thyroid, Lung (NSCLC). * **Pulsatile secondarys:** RCC and Follicular Thyroid Carcinoma.

Q: Which tumor shows a biphasic pattern on histology?

Synovial sarcoma. **Explanation:** **Synovial Sarcoma** is the classic example of a **biphasic tumor** in soft tissue pathology [1]. The term "biphasic" refers to the presence of two distinct cell populations: 1. **Epithelial cells:** Cuboidal to columnar cells that often form gland-like structures or nests. 2. **Spindle cells:** Uniform, small cells arranged in dense, cellular fascicles. *Note: Some synovial sarcomas are "monophasic," consisting only of spindle cells, but the biphasic pattern is pathognomonic [1].* **Analysis of Incorrect Options:** * **A. Rhabdomyosarcoma:** Characterized by **rhabdomyoblasts** (eccentric nuclei and eosinophilic cytoplasm) and "tadpole" or "strap" cells. It does not show an epithelial component. * **C. Osteosarcoma:** Defined by the production of **osteoid** (unmineralized bone) by malignant mesenchymal cells. It is a monophasic mesenchymal tumor. * **D. Neurofibroma:** A benign nerve sheath tumor composed of a mixture of Schwann cells, fibroblasts, and perineural cells in a **myxoid stroma** (shredded-carrot appearance), lacking a biphasic epithelial-spindle arrangement. **High-Yield Clinical Pearls for NEET-PG:** * **Cytogenetics:** Synovial sarcoma is strongly associated with the **t(X;18) (p11;q11)** translocation, resulting in the **SS18-SSX** fusion gene [1]. * **Location:** Despite the name, it rarely arises from the intra-articular synovial membrane; it typically occurs in the deep soft tissues near large joints (especially the knee) in young adults [1]. * **IHC Markers:** Positive for **Cytokeratin (CK)** and **EMA** (in the epithelial component) and **TLE1** (highly sensitive and specific marker). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1225-1226.

Question 1

Which of the following statements is FALSE regarding ossifying fibroma?

Accepted Answer

Maxilla is affected more frequently than the mandible

Answer

Affects individuals in the third to fourth decade of life

Answer

Presents as a circumscribed radiopacity

Answer

Exhibits continuous growth

Question 2

What is the origin of the Pindborg tumour?

Accepted Answer

Stratum intermedium

Answer

Reduced enamel epithelium

Answer

Dental lamina

Answer

All of the above

Question 3

On a routine radiographic exam, a well-defined radiolucent lesion was seen in the body of the mandible of a 17-year-old boy. At the time of operation, it proved to be an empty cavity. This is a(an) ____?

Accepted Answer

Traumatic bone cyst

Answer

Osteoporotic bone marrow

Answer

Aneurysmal bone cyst

Answer

Odontogenic keratocyst

Question 4

MIC-2 is a marker of?

Accepted Answer

Ewing sarcoma

Answer

Chronic lymphocytic leukemia

Answer

Mantle cell lymphoma

Answer

All of these

Question 5

Which of the following is described as a unicentric, non-functional, anatomically benign, and clinically persistent tumor?

Accepted Answer

Ameloblastoma

Answer

CEOT

Answer

Enameloma

Answer

Odontorna

Question 6

If both parents have Achondroplasia, what are their chances of having a child without Achondroplasia?

Accepted Answer

25%

Answer

0%

Answer

50%

Answer

100%

Question 7

Which of the following carcinomas metastasizes to bone EXCEPT:

Accepted Answer

Liver

Answer

Thyroid

Answer

Prostate

Answer

Breast

Question 8

Osteoclastic giant cells are seen in all conditions except?

Accepted Answer

Aneurysmal bone cyst

Answer

Osteoclastoma

Answer

Osteoblastoma

Answer

Chondroblastoma

Question 9

Duchenne Muscular Dystrophy is a disease of which component?

Accepted Answer

Sarcolemmal proteins

Answer

Neuromuscular junction

Answer

Muscle contractile proteins

Answer

Disuse atrophy due to muscle weakness

Question 10

Which tumor shows a biphasic pattern on histology?

Accepted Answer

Synovial sarcoma

Answer

Rhabdomyosarcoma

Answer

Osteosarcoma

Answer

Neurofibroma

Bone and Soft Tissue Pathology — MCQs

Bone and Soft Tissue Pathology — MCQs

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