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10. Pathology and Oncology MCQs

Practice Set 339 of 351

This practice set contains high-yield board review questions covering key concepts in 10. Pathology and Oncology. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 6761

Topic: 10. Pathology and Oncology

A 16-year-old boy with multiple hereditary exostoses (MHE) is being evaluated. Which of the following characteristics is most suggestive of malignant transformation of an osteochondroma in an adult patient?

. Cartilage cap thickness of 1 cm on MRI
. Growth of the lesion after skeletal maturity
. Multiple sessile lesions in the metaphyseal regions
. Pain relieved by NSAIDs
. Stalk pointing away from the joint line

Correct Answer & Explanation

. Growth of the lesion after skeletal maturity

Explanation

Growth of an osteochondroma after skeletal maturity or a cartilage cap thickness greater than 2 cm in an adult is highly suspicious for malignant transformation to secondary chondrosarcoma. Pain and new neurovascular symptoms are also red flags.

Question 6762

Topic: 10. Pathology and Oncology

A 55-year-old male presents with a deep, slow-growing painless mass in his thigh. Biopsy reveals mature adipocytes with focal nuclear atypia and hyperchromatic stromal cells.

Which genetic abnormality is the hallmark of this lesion?

. t(X;18) translocation
. MDM2 and CDK4 gene amplification on ring chromosome 12
. t(12;16) translocation (FUS-DDIT3)
. t(2;13) translocation (PAX3-FOXO1)
. t(11;22) translocation (EWS-FLI1)

Correct Answer & Explanation

. MDM2 and CDK4 gene amplification on ring chromosome 12

Explanation

Atypical lipomatous tumors (well-differentiated liposarcomas) are characterized by amplification of the MDM2 and CDK4 genes, usually on ring or giant rod chromosomes derived from chromosome 12. This distinguishes them from benign lipomas.

Question 6763

Topic: 10. Pathology and Oncology

A 19-year-old male presents with a painless, hard mass about the medial proximal tibia. Radiographs confirm a pedunculated osteochondroma pointing away from the joint.

He complains of occasional snapping over the mass. What is the most common non-malignant complication of an osteochondroma in this location?

. Pathological fracture through the base
. Deep vein thrombosis
. Formation of an overlying reactive bursa (bursitis)
. Pseudoaneurysm of the popliteal artery
. Common peroneal nerve palsy

Correct Answer & Explanation

. Formation of an overlying reactive bursa (bursitis)

Explanation

The most common complication of an osteochondroma is the formation of a symptomatic reactive bursa (exostosis bursitis) over the cartilaginous cap. Vascular and neurologic complications can occur but are less common.

Question 6764

Topic: 10. Pathology and Oncology

Which of the following anatomic locations is most strongly associated with a higher risk of local recurrence and potential for dedifferentiation in atypical lipomatous tumors (ALT/WDLPS)?

. Subcutaneous tissue of the thigh
. Intramuscular space of the deltoid
. Retroperitoneum
. Superficial fascia of the back
. Dermal layer of the scalp

Correct Answer & Explanation

. Retroperitoneum

Explanation

ALTs located in deep anatomical spaces such as the retroperitoneum or mediastinum have a much higher risk of repeated local recurrences. These repeated recurrences significantly increase the risk of dedifferentiation into higher-grade sarcomas.

Question 6765

Topic: 10. Pathology and Oncology

A 25-year-old male with a known distal femoral osteochondroma notes recent enlargement.

An MRI is ordered. Which finding would most strongly indicate a biopsy for suspected malignant transformation?

. Cartilage cap measuring 0.5 cm in thickness
. Edema in the adjacent vastus medialis
. Corticomedullary continuity with the host bone
. Cartilage cap measuring > 2.0 cm with irregular enhancement
. Low signal intensity of the stalk on T1-weighted images

Correct Answer & Explanation

. Cartilage cap measuring > 2.0 cm with irregular enhancement

Explanation

A cartilage cap thickness greater than 2 cm in a skeletally mature adult is highly suspicious for malignant transformation into secondary chondrosarcoma. Irregular contrast enhancement of the cap or a new soft-tissue mass further supports this diagnosis.

Question 6766

Topic: 10. Pathology and Oncology

How can primary synovial chondromatosis be distinguished radiographically and histologically from secondary synovial chondromatosis (such as that caused by severe osteoarthritis)?

. Primary typically has a few, large, irregularly sized bodies
. Primary typically has numerous uniform calcifications and cellular atypia
. Primary exhibits an inflammatory synovial infiltrate without chondrocytes
. Secondary shows high MDM2 amplification
. Primary only affects the axial skeleton

Correct Answer & Explanation

. Primary typically has a few, large, irregularly sized bodies

Explanation

Primary synovial chondromatosis is characterized by numerous, uniform-sized nodules that may exhibit mild, benign cellular atypia. Secondary chondromatosis usually features a few, large, irregularly sized bodies resulting from fragmented osteophytes in the setting of degenerative joint disease.

Question 6767

Topic: 10. Pathology and Oncology

A 16-year-old boy presents with a painless, hard mass around his distal femur. Imaging shows a sessile lesion with cortico-medullary continuity with the host bone.

The pathogenesis of this condition is most commonly associated with a mutation in a gene responsible for the synthesis of which of the following?

. Type I collagen
. Heparan sulfate
. Fibroblast growth factor receptor 3
. Beta-catenin
. Bone morphogenetic protein

Correct Answer & Explanation

. Heparan sulfate

Explanation

Osteochondromas are associated with mutations in the EXT1 or EXT2 genes, which are tumor suppressor genes. These genes encode glycosyltransferases essential for the biosynthesis of heparan sulfate, leading to disordered physeal growth.

Question 6768

Topic: 10. Pathology and Oncology

A 60-year-old woman presents with a slowly enlarging, painless mass deep in her right thigh. Biopsy reveals mature adipocytes with focal cellular atypia and hyperchromatic stromal cells.

Which of the following genetic abnormalities is most characteristic of this tumor?

. t(11;22) EWS-FLI1
. t(X;18) SYT-SSX
. MDM2 and CDK4 amplification
. GNAS1 mutation
. t(12;16) FUS-DDIT3

Correct Answer & Explanation

. MDM2 and CDK4 amplification

Explanation

Atypical lipomatous tumors (ALTs) and well-differentiated liposarcomas are characterized by the amplification of MDM2 and CDK4 genes on chromosome 12q13-15. This molecular finding is diagnostic and differentiates them from benign lipomas.

Question 6769

Topic: 10. Pathology and Oncology

A 40-year-old man presents with chronic knee pain, swelling, and mechanical locking. Radiographs show multiple, uniform, calcified loose bodies within the joint capsule.

What is the underlying pathophysiology of this primary condition?

. Fragmentation of osteophytes secondary to severe osteoarthritis
. Benign nodular cartilaginous metaplasia of synovial tissue
. Deposition of monosodium urate crystals
. Proliferation of hemosiderin-laden macrophages
. Autoimmune destruction of articular cartilage

Correct Answer & Explanation

. Benign nodular cartilaginous metaplasia of synovial tissue

Explanation

Primary synovial chondromatosis involves the benign nodular cartilaginous metaplasia of synovial connective tissue. It is idiopathic and not caused by joint trauma or degenerative changes.

Question 6770

Topic: 10. Pathology and Oncology

A 35-year-old man with a known history of an asymptomatic distal femur osteochondroma presents with new-onset pain and enlargement of the mass. An MRI is obtained. Which of the following findings is most predictive of malignant transformation to a secondary chondrosarcoma?

. Cortical irregularity
. Cartilage cap thickness of 2.5 cm
. Presence of a stalk (pedunculated)
. Location in the metaphysis
. Edema in the adjacent vastus medialis

Correct Answer & Explanation

. Cartilage cap thickness of 2.5 cm

Explanation

In a skeletally mature adult, a cartilage cap thicker than 2 cm on MRI is highly suspicious for malignant transformation to a secondary chondrosarcoma. Benign lesions typically have a cap less than 1 cm thick.

Question 6771

Topic: 10. Pathology and Oncology

Which of the following best explains why an "atypical lipomatous tumor" and a "well-differentiated liposarcoma" are classified differently despite having identical histological features?

. Presence of metastatic potential
. Rate of cellular mitosis
. Anatomical location of the tumor
. Patient age at presentation
. Response to radiation therapy

Correct Answer & Explanation

. Anatomical location of the tumor

Explanation

Atypical lipomatous tumor (ALT) and well-differentiated liposarcoma share identical histology. The terminology differs based on anatomical location; lesions in deep resectable areas (extremities) are ALTs, while those in unresectable areas (retroperitoneum) are called well-differentiated liposarcomas due to higher morbidity and mortality.

Question 6772

Topic: 10. Pathology and Oncology

A 45-year-old patient with known, long-standing primary synovial chondromatosis of the hip returns with rapidly progressive pain. Advanced imaging is ordered. Which of the following MRI findings is the most reliable indicator of malignant transformation to a synovial chondrosarcoma?

. Increase in the number of intra-articular loose bodies
. Erosion of the articular cartilage
. Extensive marrow invasion of the femoral head or acetabulum
. Presence of "ring-and-arc" calcifications
. Joint effusion with synovitis

Correct Answer & Explanation

. Extensive marrow invasion of the femoral head or acetabulum

Explanation

Malignant transformation of synovial chondromatosis to chondrosarcoma is rare (~5%). The most reliable imaging indicator of this transformation is invasion into the adjacent bone marrow, whereas simple erosions or increased loose bodies are typical of benign disease.

Question 6773

Topic: 10. Pathology and Oncology

When evaluating an intramuscular lipomatous tumor of the thigh on MRI, which of the following features is most suggestive of an Atypical Lipomatous Tumor (ALT) rather than a simple benign lipoma?

. Size less than 5 cm
. Homogeneous suppression on STIR sequences
. Thickened, nodular septa (>2 mm) and non-adipose areas
. Subcutaneous location
. Lack of enhancement post-gadolinium

Correct Answer & Explanation

. Thickened, nodular septa (>2 mm) and non-adipose areas

Explanation

MRI features suspicious for an atypical lipomatous tumor (ALT) include a deep/intramuscular location, size >5 cm, thickened/nodular septa (>2 mm), and the presence of non-adipose tissue areas that enhance with contrast.

Question 6774

Topic: 10. Pathology and Oncology

An 18-year-old runner with a known sessile osteochondroma on the proximal medial tibia complains of recent focal pain and swelling directly over the lesion. Imaging reveals a fluid-filled sac overlying the cartilage cap with no increase in cap thickness. What is the most likely diagnosis?

. Secondary chondrosarcoma
. Malignant fibrous histiocytoma
. Exostosis bursa (bursitis)
. Aneurysmal bone cyst
. Pathologic fracture of the stalk

Correct Answer & Explanation

. Exostosis bursa (bursitis)

Explanation

Mechanical irritation of adjacent soft tissues over an osteochondroma can lead to the formation of a bursa (exostosis bursa). Inflammation of this bursa is a common, benign cause of new-onset pain and swelling, mimicking malignant transformation.

Question 6775

Topic: 10. Pathology and Oncology

A 52-year-old man is diagnosed with an atypical lipomatous tumor (ALT) in the anterior compartment of his thigh. There is no evidence of metastasis. What is the most appropriate surgical treatment approach?

. Amputation
. Neoadjuvant chemotherapy followed by wide local excision
. Marginal excision (shelling out) with preservation of adjacent critical structures
. Wide excision with a 5 cm margin including sacrifice of the femoral nerve
. Intralesional curettage and bone grafting

Correct Answer & Explanation

. Marginal excision (shelling out) with preservation of adjacent critical structures

Explanation

ALTs in the extremity do not possess metastatic potential, although they have a risk of local recurrence. Marginal excision is the standard of care to minimize morbidity, reserving wide resection for cases where it does not cause significant functional deficit.

Question 6776

Topic: 10. Pathology and Oncology

A 28-year-old male with multiple hereditary exostoses presents with a newly enlarging mass around his right knee.

MRI shows an osteochondroma with a cartilaginous cap. What cartilage cap thickness on MRI is most highly suggestive of secondary malignant transformation to chondrosarcoma in an adult?

. 0.5 cm
. 0.8 cm
. 1.2 cm
. 2.5 cm
. Cap thickness does not correlate with malignancy

Correct Answer & Explanation

. 2.5 cm

Explanation

In adults, a cartilage cap thickness greater than 1.5 to 2.0 cm on MRI is highly suspicious for malignant transformation to secondary chondrosarcoma. Excisional biopsy or wide resection is typically warranted for these enlarging lesions.

Question 6777

Topic: 10. Pathology and Oncology

Primary synovial chondromatosis of the knee in a 40-year-old male is best described by which of the following histological processes?

. Reactive hyperplasia of subsynovial fibroblasts
. Metaplasia of the synovial membrane
. Dislodgement of intra-articular osteophytic fragments
. Deposition of monosodium urate crystals
. Proliferation of multinucleated giant cells

Correct Answer & Explanation

. Metaplasia of the synovial membrane

Explanation

Primary synovial chondromatosis is a rare, benign condition that occurs via chondroid metaplasia of the synovial membrane. This leads to the formation of multiple cartilaginous nodules that frequently detach to become loose bodies.

Question 6778

Topic: 10. Pathology and Oncology

A 55-year-old female presents with a deep-seated intramuscular thigh mass. Biopsy reveals an atypical lipomatous tumor.

Which of the following genetic alterations is diagnostic for this specific lesion?

. t(11;22) translocation
. t(X;18) translocation
. MDM2 and CDK4 gene amplification
. t(12;16) translocation
. GNAS mutation

Correct Answer & Explanation

. MDM2 and CDK4 gene amplification

Explanation

Atypical lipomatous tumors (ALTs) and well-differentiated liposarcomas are characterized by the amplification of MDM2 and CDK4 genes on chromosome 12q. This molecular signature reliably differentiates them from benign lipomas.

Question 6779

Topic: Bone Tumors

Multiple hereditary exostoses (MHE) is an autosomal dominant condition linked to mutations in EXT1 and EXT2. These genes encode for glycosyltransferases primarily involved in the synthesis of which of the following?

. Chondroitin sulfate
. Heparan sulfate
. Hyaluronic acid
. Keratan sulfate
. Type II collagen

Correct Answer & Explanation

. Heparan sulfate

Explanation

EXT1 and EXT2 encode for glycosyltransferases responsible for the synthesis of heparan sulfate proteoglycans. A deficiency in heparan sulfate disrupts Indian hedgehog (Ihh) signaling at the growth plate, triggering the formation of osteochondromas.

Question 6780

Topic: 10. Pathology and Oncology

A 45-year-old patient with a long-standing history of multiple loose bodies in the hip joint diagnosed as primary synovial chondromatosis presents with sudden onset of severe rest pain and rapid swelling.

What is the most feared complication that must be ruled out?

. Septic arthritis
. Osteonecrosis of the femoral head
. Malignant transformation to chondrosarcoma
. Pathologic fracture of the femoral neck
. Rapidly destructive osteoarthritis

Correct Answer & Explanation

. Malignant transformation to chondrosarcoma

Explanation

Primary synovial chondromatosis carries a documented risk of malignant transformation to secondary chondrosarcoma in approximately 5% of long-standing cases. Sudden exacerbation of symptoms, particularly rest pain, warrants advanced imaging and biopsy.

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