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10. Pathology and Oncology MCQs

Practice Set 342 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 6821

Topic: 10. Pathology and Oncology

A 45-year-old male with advanced Ankylosing Spondylitis develops progressive lower back pain. Radiographs reveal a destructive, radiolucent lesion at the T12-L1 discovertebral junction with sclerotic margins.

What is the most likely diagnosis?

. Pyogenic discitis
. Tuberculous spondylitis
. Anderson lesion
. Metastatic prostate cancer
. Multiple myeloma

Correct Answer & Explanation

. Anderson lesion

Explanation

An Anderson lesion is an inflammatory or traumatic pseudarthrosis that occurs in the ankylosed spine. It often presents as a destructive discovertebral lesion with reactive sclerosis and is managed with surgical stabilization if painful and unstable.

Question 6822

Topic: 10. Pathology and Oncology

A 55-year-old female with a long history of primary synovial chondromatosis of the hip presents with new, rapidly worsening rest pain and progressive joint destruction on radiographs. What is the most likely complication?

. Spontaneous bacterial seeding (Septic arthritis)
. Malignant transformation to secondary chondrosarcoma
. Development of pigmented villonodular synovitis (PVNS)
. Avascular necrosis of the femoral head
. Transformation into an extra-articular osteochondroma

Correct Answer & Explanation

. Malignant transformation to secondary chondrosarcoma

Explanation

Primary synovial chondromatosis has a known, albeit rare, risk of malignant transformation into secondary synovial chondrosarcoma (approximately 5% incidence). Rapid clinical deterioration and bone destruction are hallmark signs.

Question 6823

Topic: 10. Pathology and Oncology

An atypical lipomatous tumor (ALT) and a well-differentiated liposarcoma (WDLS) are histologically identical. The terminology differs based purely on anatomical location. In which location is the term "well-differentiated liposarcoma" utilized due to the high risk of unresectability and mortality from local recurrence?

. Subcutaneous tissue of the anterior thigh
. Intramuscular compartment of the biceps brachii
. Retroperitoneum
. Subfascial posterior calf
. Plantar aspect of the foot

Correct Answer & Explanation

. Retroperitoneum

Explanation

The term well-differentiated liposarcoma (WDLS) is reserved for lesions in the retroperitoneum or mediastinum, where wide excision is frequently impossible, leading to high local recurrence rates and death. In the appendicular skeleton, they are termed atypical lipomatous tumors (ALT).

Question 6824

Topic: Bone Tumors

Which of the following is a strict diagnostic requirement for the radiographic identification of a benign osteochondroma?

. Separation from the host bone medullary canal by a thick sclerotic rim
. Medullary and cortical continuity with the underlying host bone
. Presence of a thick, layered "onion skin" periosteal reaction
. Intralesional popcorn calcification with cortical destruction
. A central nidus measuring less than 1.5 cm with surrounding sclerosis

Correct Answer & Explanation

. Medullary and cortical continuity with the underlying host bone

Explanation

The pathognomonic radiographic hallmark of an osteochondroma is direct continuity of its cortex and medullary cavity with the cortex and medullary cavity of the host bone.

Question 6825

Topic: 10. Pathology and Oncology

Primary synovial chondromatosis typically involves which of the following pathophysiological processes?

. Detachment of marginal osteophytes in advanced degenerative joint disease
. Benign metaplasia of synovial connective tissue into active chondrocytes
. Autoimmune destruction of articular cartilage yielding free fragments
. Urate crystalline deposition within the synovial lining causing necrosis
. Proliferation of multinucleated giant cells and hemosiderin deposition

Correct Answer & Explanation

. Benign metaplasia of synovial connective tissue into active chondrocytes

Explanation

Primary synovial chondromatosis is a benign neoplastic process involving spontaneous chondroid metaplasia of the synovial membrane, producing cartilaginous nodules that may detach and ossify.

Question 6826

Topic: Soft Tissue Tumors & Metastasis

A 40-year-old male notes a slowly enlarging mass in his trapezius muscle. MRI reveals a well-defined mass with signal intensity identical to subcutaneous fat, interspersed with distinct, thick striations of skeletal muscle fibers. What is the most likely diagnosis?

. Atypical lipomatous tumor
. Intramuscular lipoma
. Spindle cell lipoma
. Myxoid liposarcoma
. Hibernoma

Correct Answer & Explanation

. Intramuscular lipoma

Explanation

An intramuscular lipoma characteristically infiltrates between skeletal muscle bundles. On MRI, this appears as a predominately fatty mass with traversing linear striations representing entrapped muscle fibers, distinct from the thick septations seen in liposarcomas.

Question 6827

Topic: 10. Pathology and Oncology

A 55-year-old male presents with a large, deep intramuscular mass in his right thigh. Biopsy reveals mature adipocytes with focal areas of hyperchromatic, atypical stromal cells.

Which of the following molecular or genetic findings is diagnostic for distinguishing this lesion from a benign lipoma?

. t(X;18) translocation
. MDM2 and CDK4 gene amplification
. t(11;22) translocation
. FUS-CHOP gene fusion
. Beta-catenin mutation

Correct Answer & Explanation

. MDM2 and CDK4 gene amplification

Explanation

Atypical lipomatous tumors (well-differentiated liposarcomas) are characterized by the amplification of MDM2 and CDK4 genes on chromosome 12q13-15. This genetic finding reliably distinguishes them from benign lipomas, which lack these amplifications.

Question 6828

Topic: 10. Pathology and Oncology

A 25-year-old male with a known distal femur osteochondroma reports newly onset pain and a palpable increase in the size of the mass. MRI reveals a cartilage cap thickness of 2.8 cm with soft tissue edema. What is the next best step in management?

. Observation and repeat MRI in 6 months
. Core needle biopsy
. Wide surgical resection
. Denosumab therapy
. Intralesional curettage and bone grafting

Correct Answer & Explanation

. Wide surgical resection

Explanation

In a skeletally mature patient, a cartilage cap thicker than 2 cm (or 1.5 cm in some texts) combined with new pain and growth is highly suspicious for malignant transformation to secondary chondrosarcoma. Wide surgical resection is the definitive treatment.

Question 6829

Topic: 10. Pathology and Oncology

A 40-year-old male presents with chronic knee catching and pain. Radiographs reveal numerous uniformly sized, calcified loose bodies within the joint space.

What is the primary pathophysiologic mechanism for this condition?

. Degenerative shedding of articular cartilage
. Benign metaplasia of the synovial membrane
. Autoimmune proliferation of the synovium
. Deposition of calcium pyrophosphate crystals
. Chronic granulomatous infection

Correct Answer & Explanation

. Benign metaplasia of the synovial membrane

Explanation

Primary synovial chondromatosis is a benign neoplastic process caused by cartilaginous metaplasia of the synovial membrane. This results in the formation of multiple uniformly sized cartilaginous nodules that may detach and ossify.

Question 6830

Topic: 10. Pathology and Oncology

A 14-year-old boy presents with multiple bony prominences around his knees and ankles. Family history is positive for a similar condition. Which of the following statements regarding his diagnosis is most accurate?

. The condition is inherited in an autosomal recessive pattern.
. It is caused by mutations in the EXT1 and EXT2 tumor suppressor genes.
. The overall risk of malignant transformation is greater than 50%.
. The lesions predominantly form within the epiphysis of long bones.
. It is characterized by fibrous dysplasia and endocrine abnormalities.

Correct Answer & Explanation

. It is caused by mutations in the EXT1 and EXT2 tumor suppressor genes.

Explanation

Multiple hereditary exostoses (MHE) is an autosomal dominant condition linked to mutations in the EXT1 and EXT2 genes, which are involved in heparan sulfate synthesis. The risk of malignant transformation to chondrosarcoma is approximately 1-5%, much lower than 50%.

Question 6831

Topic: 10. Pathology and Oncology

A 50-year-old female presents with a soft, painless, mobile mass on her upper back. On MRI, the mass is well-circumscribed, hyperintense on T1-weighted images, and demonstrates complete signal loss on Short Tau Inversion Recovery (STIR) sequences. What is the most likely diagnosis?

. Intramuscular myxoma
. Benign lipoma
. Schwannoma
. Epidermal inclusion cyst
. Hemangioma

Correct Answer & Explanation

. Benign lipoma

Explanation

A benign lipoma is composed of mature adipose tissue, which appears hyperintense on T1-weighted MRI. Complete suppression of the signal on fat-saturated (STIR) sequences is pathognomonic for fat.

Question 6832

Topic: 10. Pathology and Oncology

A 38-year-old male with a history of primary synovial chondromatosis of the hip, treated with arthroscopic synovectomy 4 years ago, presents with rapidly worsening pain. Radiographs show a destructive, lytic lesion invading the acetabulum with an associated soft tissue mass. What is the most likely diagnosis?

. Recurrent benign synovial chondromatosis
. Secondary chondrosarcoma
. Pigmented villonodular synovitis (PVNS)
. Osteosarcoma
. Septic arthritis

Correct Answer & Explanation

. Secondary chondrosarcoma

Explanation

Primary synovial chondromatosis carries a rare (up to 5%) risk of malignant transformation into secondary chondrosarcoma. Rapidly worsening symptoms, bone destruction, and soft tissue invasion are hallmarks of this malignant change.

Question 6833

Topic: Bone Tumors

A 12-year-old boy presents with a hard, painless bump on his distal femur. Radiographs show a pedunculated bony exostosis pointing away from the joint.

What is the pathognomonic radiographic feature required to confirm an osteochondroma?

. Cortical expansion with ground-glass matrix
. Medullary and cortical continuity with the host bone
. Sunburst periosteal reaction
. A radiolucent nidus surrounded by dense reactive sclerosis
. Stippled calcifications confined to the epiphysis

Correct Answer & Explanation

. Medullary and cortical continuity with the host bone

Explanation

The hallmark of an osteochondroma is the direct continuity of both the cortex and the medullary cavity of the lesion with those of the underlying host bone.

Question 6834

Topic: 10. Pathology and Oncology

A 60-year-old male is diagnosed with an atypical lipomatous tumor (well-differentiated liposarcoma) located deep in the retroperitoneum. Why is the prognosis for this retroperitoneal lesion poorer than for a histologically identical lesion in the deep soft tissues of the thigh?

. Extremity tumors have intrinsically higher metastatic potential.
. Retroperitoneal tumors frequently spread via hematogenous routes to the lungs.
. Retroperitoneal location precludes wide surgical margins, leading to higher rates of local recurrence and dedifferentiation.
. Retroperitoneal tumors lack MDM2 gene amplification.
. Extremity tumors respond exceptionally well to neoadjuvant chemotherapy.

Correct Answer & Explanation

. Retroperitoneal location precludes wide surgical margins, leading to higher rates of local recurrence and dedifferentiation.

Explanation

Atypical lipomatous tumors/well-differentiated liposarcomas do not typically metastasize but can dedifferentiate over time. In the retroperitoneum, achieving wide, negative surgical margins is difficult, leading to multiple local recurrences and a higher risk of dedifferentiation into a higher-grade sarcoma.

Question 6835

Topic: 10. Pathology and Oncology

Primary synovial chondromatosis is a benign neoplasm characterized by synovial metaplasia. Which specific genetic fusion is most frequently implicated in the pathogenesis of this disease?

. t(X;18) causing SYT-SSX fusion
. t(11;22) causing EWS-FLI1 fusion
. t(12;16) causing FUS-CHOP fusion
. FN1-ACVR2A or FN1-NCOA2 fusions
. USP6 gene rearrangements

Correct Answer & Explanation

. FN1-ACVR2A or FN1-NCOA2 fusions

Explanation

Recent molecular studies have identified recurrent fusions involving the Fibronectin 1 (FN1) gene, most commonly FN1-ACVR2A or FN1-NCOA2, as the driving genetic abnormalities in primary synovial chondromatosis.

Question 6836

Topic: Bone Tumors

A 10-year-old boy presents with an incidentally discovered sessile osteochondroma of the proximal humerus. Over the next several years of skeletal growth, how will the relative position of this lesion change?

. It will migrate toward the diaphysis as the bone elongates.
. It will migrate toward the epiphysis.
. It will slowly invade the joint space.
. It will migrate anteriorly due to muscular traction.
. It will remain completely stationary relative to the physis.

Correct Answer & Explanation

. It will migrate toward the diaphysis as the bone elongates.

Explanation

Osteochondromas arise from aberrant physeal cartilage. As the host bone undergoes longitudinal growth at the physis, the osteochondroma is progressively 'left behind,' making it appear to migrate towards the diaphysis over time.

Question 6837

Topic: 10. Pathology and Oncology

A 65-year-old female with severe, end-stage osteoarthritis of the knee undergoes arthroplasty. Intraoperatively, multiple calcified loose bodies are found in the joint. Pathologic evaluation confirms secondary synovial chondromatosis. How does this condition characteristically differ from primary synovial chondromatosis?

. Secondary synovial chondromatosis presents with uniform-sized loose bodies.
. Secondary synovial chondromatosis occurs in the setting of underlying joint degeneration.
. Secondary synovial chondromatosis has a much higher rate of malignant transformation.
. Secondary synovial chondromatosis requires wide surgical resection to prevent recurrence.
. Primary synovial chondromatosis features loose bodies with concentric rings on histology, unlike secondary.

Correct Answer & Explanation

. Secondary synovial chondromatosis occurs in the setting of underlying joint degeneration.

Explanation

Secondary synovial chondromatosis results from the shedding of cartilage due to underlying joint pathology, most commonly osteoarthritis. Unlike the primary form, the loose bodies in secondary chondromatosis are typically fewer in number, of varying sizes, and have concentric rings of ossification.

Question 6838

Topic: 10. Pathology and Oncology

A 55-year-old man presents with a deep 12 cm thigh mass. Biopsy shows mature adipose tissue with focal nuclear atypia. Molecular testing reveals MDM2 gene amplification. What is the most appropriate management?

. Simple enucleation
. Marginal excision with observation
. Neoadjuvant radiation followed by excision
. Radical amputation
. Neoadjuvant chemotherapy

Correct Answer & Explanation

. Marginal excision with observation

Explanation

MDM2 amplification confirms an Atypical Lipomatous Tumor (ALT) / Well-Differentiated Liposarcoma. In the extremity, ALTs have no metastatic potential, so marginal excision that preserves critical structures is adequate management, though local recurrence remains a risk.

Question 6839

Topic: 10. Pathology and Oncology

A 22-year-old male with multiple hereditary exostoses (MHE) reports new-onset, enlarging mass and pain around his right proximal femur. Which of the following is the strongest indicator of malignant transformation on imaging?

. A cartilage cap thickness of 1.2 cm on MRI
. Growth of the lesion after skeletal maturity
. Presence of a stalk connecting to the medullary canal
. Development of an overlying bursa
. Marrow continuity with the host bone

Correct Answer & Explanation

. Growth of the lesion after skeletal maturity

Explanation

Growth of an osteochondroma after skeletal maturity or a cartilage cap >1.5-2.0 cm on MRI strongly suggests malignant transformation to a secondary chondrosarcoma. Observation is no longer appropriate for growing, painful lesions in adults.

Question 6840

Topic: 10. Pathology and Oncology

A 12-year-old boy is diagnosed with Multiple Hereditary Exostoses (MHE). Genetic testing is likely to show a mutation in genes responsible for which of the following cellular processes?

. Type I collagen synthesis
. Fibroblast growth factor receptor 3 (FGFR3) activation
. Heparan sulfate synthesis
. MDM2 amplification
. Runx2 transcription factor regulation

Correct Answer & Explanation

. Heparan sulfate synthesis

Explanation

MHE is an autosomal dominant condition caused by mutations in the EXT1 or EXT2 genes, which are tumor suppressors involved in heparan sulfate biosynthesis. Defective heparan sulfate leads to abnormalities in the Indian hedgehog (Ihh) signaling pathway, resulting in disordered chondrocyte proliferation.

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