Bone and Soft Tissue Pathology — MCQs

A 13-year-old boy, previously healthy, presents with a 1-month history of right leg pain, without trauma or recent illness. Physical examination reveals warmth, tenderness, and increased circumference of the right thigh compared to the left. His temperature is 39°C. A radiograph shows a 6-cm expansile mass in the diaphyseal region of the right lower femur, extending into soft tissue and covered by reactive bone. Microscopic examination of the mass biopsy reveals sheets of primitive cells with small, uniform nuclei and scant cytoplasm. Karyotypic analysis shows a t(11;22) translocation. What is the most likely diagnosis?

Q356

Ewing's sarcoma arises from which of the following tissues?

Q357

What is the typical chromosomal complement in primary chondrosarcoma cells?

Q358

Which of the following soft tissue sarcomas does not typically have a propensity for lymphatic spread?

Q359

In Ewing's sarcoma, histology shows small round cells that are filled with which of the following?

Q360

Which of the following is not a polyostotic bone lesion?

Bone and Soft Tissue Pathology Indian Medical PG Practice Questions and MCQs

Question 351: Osteosclerosis is a feature of which of the following conditions?

A. Hyperparathyroidism
B. Paget's Disease
C. Rickets
D. Osteopetrosis (Correct Answer)

Explanation: ***Osteopetrosis*** - This condition is characterized by **diffuse, generalized osteosclerosis** due to defective osteoclast function [1]. - Impaired bone resorption results in **uniformly increased bone density** throughout the skeleton, creating "marble bone" appearance [1]. - This is the **classic cause of generalized osteosclerosis** [1]. *Rickets* - Rickets is caused by **vitamin D deficiency** leading to **impaired bone mineralization** in children. - Results in **bone softening (osteomalacia)** and **decreased density**, the opposite of osteosclerosis. *Hyperparathyroidism* - Causes **increased bone resorption** due to elevated parathyroid hormone levels [2]. - Leads to **osteopenia** or **osteoporosis** (decreased bone density), not osteosclerosis [2]. *Paget's Disease* - Characterized by **disorganized bone remodeling** with three phases: lytic, mixed, and sclerotic. - Can show **focal or regional osteosclerosis** in affected bones (especially in late sclerotic phase). - However, unlike osteopetrosis, it causes **localized rather than diffuse** sclerosis, with **disorganized architecture** (cotton wool appearance), not uniform increased density. **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. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, p. 1194.

Question 352: All of the following are diaphyseal tumors except:

A. Histiocytosis
B. Fibrosarcoma
C. Aneurysmal bone cyst (Correct Answer)
D. Ewing's sarcoma

Explanation: ***Aneurysmal bone cyst*** - This is primarily a **metaphyseal lesion**, though it can extend into the diaphysis or epiphysis [1]. - While it can occur in various bones, its predilection for the metaphysis distinguishes it from strictly diaphyseal tumors [1]. *Ewing's sarcoma* - This highly aggressive tumor characteristically arises in the **diaphysis** of long bones, particularly the femur, tibia, and humerus. - It classically presents with an **'onion-skin' appearance** on plain radiographs due to periosteal reaction. *Histiocytosis* - **Langerhans cell histiocytosis** commonly affects the **diaphysis** of long bones and flat bones like the skull. - It can manifest as lytic lesions within the diaphysis, often with surrounding sclerosis. *Fibrosarcoma* - This is a rare malignant tumor that can arise in the **diaphysis** of long bones. - It is characterized by the production of **collagen fibers** by malignant spindle cells. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1206-1208.

Question 353: Which of the following statements is true regarding eosinophilic granuloma?

A. Eosinophilic granuloma primarily affects adults.
B. Eosinophilic granuloma is characterized by a predominant neutrophilic infiltrate.
C. Eosinophilic granuloma is associated with Langerhans cell histiocytosis. (Correct Answer)
D. Eosinophilic granuloma is a benign condition that resolves spontaneously.

Explanation: ***Eosinophilic granuloma is associated with Langerhans cell histiocytosis.*** [1] - **Eosinophilic granuloma** is the most benign and localized form of **Langerhans cell histiocytosis (LCH)**, a clonal proliferative disorder of Langerhans cells. - It involves isolated bone lesions or, less commonly, pulmonary involvement, and is characterized by an infiltrate of Langerhans cells, eosinophils, and other inflammatory cells. [1] *Eosinophilic granuloma primarily affects adults.* - While it can occur in adults, **eosinophilic granuloma** is the most common form of LCH and primarily affects **children and adolescents**. - Its peak incidence is typically in the 5-15 year age range. *Eosinophilic granuloma is characterized by a predominant neutrophilic infiltrate.* - The characteristic histological feature of **eosinophilic granuloma** is an infiltrate consisting of **Langerhans cells** (which are CD1a and S100 positive), **eosinophils**, and often other inflammatory cells like lymphocytes and plasma cells, not neutrophils. [1] - The eosinophils are typically numerous, giving the lesion its name. *Eosinophilic granuloma is a benign condition that resolves spontaneously.* - While **eosinophilic granuloma** is generally considered benign and has a favorable prognosis, it does not always resolve spontaneously and often requires treatment, such as **curettage, steroid injection, or low-dose radiation**, especially for symptomatic lesions. - Spontaneous resolution is possible in some cases, but not universally characteristic. **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. 629-630.

Question 354: Generalized thickening of cortical and cancellous bones is seen in

A. Infantile hyperostosis
B. Paget's disease
C. Osteogenesis imperfecta
D. Osteopetrosis (Correct Answer)

Explanation: ***Infantile hyperostosis*** - Characterized by **generalized thickening of both cortical and cancellous bones**, typically seen in infants. - It involves **increased bone density** and can lead to various complications including pain and deformities. *Paget's disease* - Primarily affects **older adults**, leading to **disorganized bone remodeling** rather than generalized thickening. - It often presents with **localized bone enlargement** and pain, not generalized changes in infants. *Osteopetrosis* - Features **abnormally dense bones**, but typically involves **failure of bone resorption** rather than generalized thickening [1]. - While presenting with increased bone mass, it is associated with **pathological fractures** and related complications. *Osteogenesis imperfecta* - Characterized by **brittle bones** due to defective collagen synthesis rather than thickening of bones. - Patients typically experience **frequent fractures** and **blue sclera**, which are not features of generalized thickening. **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 355: A 13-year-old boy, previously healthy, presents with a 1-month history of right leg pain, without trauma or recent illness. Physical examination reveals warmth, tenderness, and increased circumference of the right thigh compared to the left. His temperature is 39°C. A radiograph shows a 6-cm expansile mass in the diaphyseal region of the right lower femur, extending into soft tissue and covered by reactive bone. Microscopic examination of the mass biopsy reveals sheets of primitive cells with small, uniform nuclei and scant cytoplasm. Karyotypic analysis shows a t(11;22) translocation. What is the most likely diagnosis?

A. Ewing sarcoma (Correct Answer)
B. Chondrosarcoma
C. Giant cell tumor
D. Metastatic carcinoma

Explanation: ***Ewing sarcoma*** - The patient's age (13-year-old), symptoms (bone pain, systemic fever), **diaphyseal location** of the tumor, and especially the characteristic histological finding of **small, uniform cells** (small round blue cell tumor) with **scant cytoplasm** point towards Ewing sarcoma. - The presence of **t(11;22)(q24;q12) translocation** resulting in the **EWSR1-FLI1 fusion gene** is a definitive diagnostic marker for Ewing sarcoma (present in ~85% of cases), distinguishing it from other bone tumors. *Chondrosarcoma* - This tumor typically affects older adults (>40 years) and arises from cartilage, showing cartilaginous matrix on histology. - It lacks the specific t(11;22) translocation seen in this patient. *Giant cell tumor* - Giant cell tumors typically occur in young adults (20-40 years) and are usually found in the **epiphyseal and metaphyseal regions** of long bones. - Histologically, they contain numerous **multinucleated giant cells** interspersed with mononuclear stromal cells, not sheets of primitive cells. *Metastatic carcinoma* - Metastatic carcinoma to bone is rare in children and usually occurs in older adults with a known primary cancer. - The histology of "sheets of primitive cells with small, uniform nuclei and scant cytoplasm" is not typical for metastatic carcinoma.

Question 356: Ewing's sarcoma arises from which of the following tissues?

A. Mesenchymal stem cells (Correct Answer)
B. Endothelial cells
C. Osteocytes
D. Primitive neuroectodermal cells

Explanation: ***Mesenchymal stem cells*** - **Ewing's sarcoma** arises from **mesenchymal stem cells (MSCs)**, which are multipotent stromal cells of mesodermal origin. - The characteristic **t(11;22)(q24;q12) translocation** results in the **EWS-FLI1 fusion gene**, which transforms mesenchymal stem cells into the malignant small round blue cells characteristic of Ewing's sarcoma. - This mesodermal/mesenchymal origin explains its predominant occurrence in **bone and soft tissues**. *Endothelial cells* - Tumors arising from **endothelial cells** are **vascular tumors** such as hemangiomas or angiosarcomas. - These have distinct histological features with vascular channel formation, unlike the solid sheets of small round blue cells seen in Ewing's sarcoma. *Osteocytes* - Tumors derived from **osteocytes** or osteoblastic cells are **bone-forming tumors**, such as osteosarcoma. - **Osteosarcoma** produces osteoid and has a distinct histology and genetic profile from Ewing's sarcoma. *Primitive neuroectodermal cells* - Historically, Ewing's sarcoma was thought to arise from **primitive neuroectodermal cells (PNETs)** due to occasional neural marker expression. - However, modern molecular studies have established that Ewing's sarcoma originates from **mesenchymal stem cells**, not neuroectodermal cells. - The term "PNET" in this context is now considered **outdated**.

Question 357: What is the typical chromosomal complement in primary chondrosarcoma cells?

A. Triploid (69 chromosomes)
B. Haploid (23 chromosomes)
C. Tetraploid (92 chromosomes)
D. Diploid (46 chromosomes) (Correct Answer)

Explanation: ***Diploid (46 chromosomes)*** - Primary **chondrosarcomas** arise from normal cartilage cells and typically maintain a **diploid chromosomal number (46 chromosomes)** [1]. - While primary chondrosarcomas may develop complex karyotypic abnormalities including structural rearrangements, they retain the diploid complement (46,XX in females or 46,XY in males) [1]. - This distinguishes them from germ cell tumors or other neoplasms that might have different ploidy states [2]. *Haploid (23 chromosomes)* - A **haploid state** (23 chromosomes) is characteristic of **germ cells** (sperm and ova), not somatic cells [2]. - Somatic tumors like chondrosarcomas are derived from diploid cells and do not exhibit haploidy. *Triploid (69 chromosomes)* - **Triploidy** involves three complete sets of chromosomes and is typically seen in certain **molar pregnancies** or non-viable embryos. - This is not a feature of chondrosarcomas or other bone tumors. *Tetraploid (92 chromosomes)* - **Tetraploidy** can occur in some cancers as a result of genome doubling events. - While some malignancies may show tetraploid populations, primary chondrosarcomas typically maintain a **diploid** state with structural chromosomal abnormalities rather than whole genome duplication [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1204-1205. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lower Urinary Tract and Male Genital System, pp. 979-980.

Question 358: Which of the following soft tissue sarcomas does not typically have a propensity for lymphatic spread?

A. Rhabdomyosarcoma
B. Synovial sarcoma
C. Malignant Peripheral Nerve Sheath Tumor (MPNST) (Correct Answer)
D. Epithelioid sarcoma

Explanation: ***Malignant Peripheral Nerve Sheath Tumor (MPNST)*** - **MPNSTs**, like most soft tissue sarcomas, primarily metastasize hematogenously to the lungs [3], and **lymphatic spread is rare** [1]. - Their origin from peripheral nerves explains their tendency for local invasion and distant blood-borne metastases rather than lymphatic involvement [1]. *Synovial sarcoma* - **Synovial sarcoma** is one of the soft tissue sarcomas that has a **higher propensity for lymphatic spread** compared to many others [2]. - While hematogenous spread is also common, clinicians should always assess regional lymph nodes when evaluating this type of tumor. *Rhabdomyosarcoma* - **Rhabdomyosarcoma** is a highly aggressive tumor, particularly in children, and frequently shows **lymphatic metastasis**, especially in parameningeal, genitourinary, and extremity sites. - Due to its high metastatic potential, regional lymph node involvement is a crucial prognostic factor. *Epithelioid sarcoma* - **Epithelioid sarcoma** is known for its **propensity for both regional lymphatic spread** and local recurrence. - The pattern of spread often mimics carcinomas, making thorough regional lymph node evaluation essential. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Peripheral Nerves and Skeletal Muscles, pp. 1250-1251. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1225-1226. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, p. 282.

Question 359: In Ewing's sarcoma, histology shows small round cells that are filled with which of the following?

A. Glycogen (Correct Answer)
B. Iron
C. Fat
D. Mucin

Explanation: ***Glycogen*** - Ewing's sarcoma cells are characterized by abundant intracellular **glycogen**, which can be demonstrated by a **PAS (Periodic Acid-Schiff) stain** that is positive and digestable by diastase. - The presence of glycogen is a key diagnostic feature, especially when differentiating it from other small round blue cell tumors. *Iron* - While iron is present in various cells, it is not a characteristic **cytoplasmic inclusion** used for the diagnosis of Ewing's sarcoma. - Iron accumulation is more typical in conditions like **hemochromatosis** or in hemosiderin-laden macrophages. *Fat* - Fat vacuoles are characteristic of **liposarcomas** and other tumors with adipocytic differentiation, not Ewing's sarcoma. - Ewing's sarcoma cells are typically primitive and undifferentiated, lacking significant lipid accumulation. *Mucin* - Mucin production is a hallmark of **adenocarcinomas** and some other epithelial tumors. - Ewing's sarcoma is a mesenchymal tumor and does not produce mucin.

Question 360: Which of the following is not a polyostotic bone lesion?

A. Osteochondroma
B. Fibrous dysplasia
C. Multiple myeloma
D. Aneurysmal bone cyst (Correct Answer)

Explanation: ***Aneurysmal bone cyst*** - An **aneurysmal bone cyst (ABC)** is typically a **solitary**, expansile, osteolytic lesion filled with blood [1]. - While it can be large and aggressive, it is **rarely polyostotic** (affecting multiple bones). *Osteochondroma* - **Multiple osteochondromas** are a common feature of **hereditary multiple exostoses**, an autosomal dominant disorder. - This condition involves the development of **cartilage-capped bony growths** on the external surface of bones. *Fibrous dysplasia* - **Fibrous dysplasia** can be **polyostotic**, especially in syndromes such as **McCune-Albright syndrome** [3], where it is associated with endocrine dysfunction and café-au-lait spots [4]. - It involves the replacement of normal bone with **fibrous tissue** and immature woven bone, leading to deformities and fractures [3]. *Multiple myeloma* - **Multiple myeloma** is a malignant proliferation of plasma cells that often presents with **multifocal lytic bone lesions** throughout the skeleton [2]. - These lesions are a hallmark of the disease and can cause **bone pain, pathological fractures**, and hypercalcemia [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1206-1208. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 617-618. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, p. 1208. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1208-1209.

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