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.

Question 1

Which cancer most commonly metastasizes to the jaw bone?

Accepted Answer

Breast

Answer

Prostatic

Answer

Lung

Answer

Kidney

Question 2

Classical 'Rain drop' lesions are seen in which of the following conditions?

Accepted Answer

Multiple myeloma

Answer

Burkitt's lymphoma

Answer

Hodgkin's lymphoma

Answer

Haemophilia

Question 3

Which of the following is NOT true about ARDS?

Accepted Answer

Pulmonary artery wedge pressure > 18 mmHg

Answer

Acute onset

Answer

PaO2/FiO2 ratio < 200 mmHg

Answer

Treatment of choice is mechanical ventilation

Question 4

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 5

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

Accepted Answer

Osteitis fibrosa

Answer

Metastasis

Answer

Histiocytosis

Answer

Asbestosis

Question 6

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 7

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 8

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 9

Adamantinoma usually arises from?

Accepted Answer

Odontogenic epithelium

Answer

Dental lamina

Answer

Endodermal tissue

Answer

Periapical tissue

Question 10

Serum alkaline phosphatase levels are increased in which of the following conditions?

Accepted Answer

Paget's disease

Answer

Osteoarthritis

Answer

Dentinogenesis imperfecta

Answer

Rheumatoid arthritis

Bone and Soft Tissue Pathology — MCQs

Bone and Soft Tissue Pathology — MCQs

On this page

Practice by Chapter

Want unlimited practice?