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10. Pathology and Oncology MCQs

Practice Set 305 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 6081

Topic: 10. Pathology and Oncology
Histological examination of a well-defined eccentric lytic proximal tibial lesion from a 19-year-old reveals lobules of myxoid tissue with stellate cells, separated by prominent fibrous septa containing multinucleated giant cells. When distinguishing this lesion from conventional chondrosarcoma, which classic histological feature is characteristically ABSENT in this benign tumor?
. Stellate-shaped spindle cells
. Multinucleated giant cells
. Abundant distinct hyaline cartilage
. A lobular architectural growth pattern
. Myxoid background stroma

Correct Answer & Explanation

. Abundant distinct hyaline cartilage

Explanation

Chondromyxoid fibroma (CMF) lacks abundant mature hyaline cartilage. Its hallmark is lobules of myxoid/chondroid tissue separated by vascularized fibrous septa with giant cells, which helps differentiate it from conventional chondrosarcoma.

Question 6082

Topic: 10. Pathology and Oncology

A 22-year-old male presents with chronic knee pain. Imaging reveals an eccentric, lytic metaphyseal lesion in the proximal tibia with a sclerotic rim. Biopsy reveals lobules of stellate cells in a myxoid background with hypercellular peripheries containing multinucleated giant cells.

What is the most appropriate definitive management?

. En bloc resection and endoprosthetic reconstruction
. Extended intralesional curettage with local adjuvant
. Neoadjuvant chemotherapy followed by wide excision
. Observation and serial radiographs
. Percutaneous radiofrequency ablation

Correct Answer & Explanation

. Extended intralesional curettage with local adjuvant

Explanation

The clinical, radiographic, and histologic descriptions are classic for chondromyxoid fibroma (CMF). The standard of care is extended intralesional curettage with local adjuvants (e.g., high-speed burring, phenol) to minimize recurrence risk.

Question 6083

Topic: 10. Pathology and Oncology

A 45-year-old woman presents with persistent, aching thigh pain not relieved by rest. Radiographs show a permeative, moth-eaten lytic lesion in the femoral diaphysis with minimal periosteal reaction.

Which of the following immunohistochemical markers is most likely to be definitively positive on biopsy?

. CD99
. S-100
. CD20
. Cytokeratin
. Epithelial Membrane Antigen (EMA)

Correct Answer & Explanation

. CD20

Explanation

The presentation and imaging are typical of primary lymphoma of bone, which predominantly affects adults over 40. The majority are diffuse large B-cell lymphomas, which reliably stain positive for the B-cell markers CD20 and CD45.

Question 6084

Topic: 10. Pathology and Oncology

An orthopedic oncologist is performing an incisional biopsy on a 60-year-old man with a destructive diaphyseal humeral lesion suspected to be a primary round blue cell tumor. To definitively diagnose and subclassify primary bone lymphoma, what special tissue handling is absolutely critical?

. Freezing the sample immediately in liquid nitrogen
. Submitting fresh tissue in saline or RPMI medium for flow cytometry
. Placing the entire sample immediately in 10% neutral buffered formalin
. Decalcifying the tissue prior to sending to pathology
. Sending for immediate cytogenetics targeting t(11;22)

Correct Answer & Explanation

. Submitting fresh tissue in saline or RPMI medium for flow cytometry

Explanation

When primary bone lymphoma is highly suspected, submitting fresh, un-decalcified tissue in RPMI medium or saline is crucial to allow for flow cytometry. This enables the evaluation of specific cell surface markers necessary to correctly subclassify the lymphoma.

Question 6085

Topic: 10. Pathology and Oncology

Which of the following descriptions best outlines the most common clinical presentation and radiographic location of a chondromyxoid fibroma?

. A 15-year-old with a central epiphyseal lytic lesion of the proximal humerus
. A 25-year-old with an eccentric diaphyseal lytic lesion of the fibula
. A 20-year-old with an eccentric metaphyseal lytic lesion of the proximal tibia
. A 45-year-old with a permeative metaphyseal lesion of the distal femur
. A 10-year-old with a well-circumscribed diaphyseal lesion with solid periosteal reaction

Correct Answer & Explanation

. A 20-year-old with an eccentric metaphyseal lytic lesion of the proximal tibia

Explanation

Chondromyxoid fibroma (CMF) is a rare benign bone tumor that typically presents in the second and third decades of life. The classic and most common radiographic location is an eccentric, lytic, well-circumscribed lesion in the metaphysis of the proximal tibia.

Question 6086

Topic: 10. Pathology and Oncology

A 15-year-old female presents with distal thigh pain. Radiographs show a destructive, bone-forming lesion in the distal femoral metaphysis with a Codman triangle. Biopsy confirms high-grade conventional osteosarcoma. What is the standard of care for this patient?

. Immediate wide surgical resection followed by radiation therapy
. Neoadjuvant chemotherapy, wide surgical resection, and adjuvant chemotherapy
. Radiation therapy alone
. Neoadjuvant radiation, intralesional curettage, and adjuvant chemotherapy
. Primary amputation without chemotherapy

Correct Answer & Explanation

. Neoadjuvant chemotherapy, wide surgical resection, and adjuvant chemotherapy

Explanation

The standard treatment for high-grade osteosarcoma is neoadjuvant chemotherapy, followed by wide surgical resection (limb salvage when possible), and concluding with adjuvant chemotherapy to treat micrometastatic disease.

Question 6087

Topic: 10. Pathology and Oncology

A 15-year-old boy presents with progressive distal femur pain. Radiographs reveal a mixed lytic and sclerotic lesion with a 'sunburst' periosteal reaction. Biopsy confirms high-grade osteosarcoma. What is the most appropriate next step in management?

. Immediate wide en bloc resection
. Neoadjuvant chemotherapy followed by wide resection
. Radiation therapy followed by intralesional curettage
. Intralesional curettage, bone grafting, and prophylactic fixation
. Immediate transfemoral amputation

Correct Answer & Explanation

. Neoadjuvant chemotherapy followed by wide resection

Explanation

The standard of care for high-grade osteosarcoma involves neoadjuvant multi-agent chemotherapy followed by wide surgical resection and subsequent adjuvant chemotherapy. This approach significantly improves overall survival and facilitates limb salvage.

Question 6088

Topic: 10. Pathology and Oncology

A 35-year-old woman presents with knee pain. Radiographs demonstrate an eccentric, lytic epiphyseal lesion extending to the subchondral bone in the proximal tibia. Biopsy reveals multinucleated giant cells within a mononuclear stroma. What is the best initial surgical treatment?

. Wide en bloc resection and endoprosthetic reconstruction
. Extended intralesional curettage with local adjuvants and polymethylmethacrylate (PMMA)
. Radiation therapy combined with denosumab
. Intralesional curettage with cancellous allograft packing
. Above-knee amputation

Correct Answer & Explanation

. Extended intralesional curettage with local adjuvants and polymethylmethacrylate (PMMA)

Explanation

Giant cell tumor of bone is a locally aggressive but benign lesion. The standard of care is extended intralesional curettage utilizing a high-speed burr and local adjuvants (e.g., phenol, argon beam), followed by filling the defect with PMMA.

Question 6089

Topic: 10. Pathology and Oncology

A 15-year-old boy presents with progressive knee pain. Radiographs demonstrate a mixed lytic and sclerotic lesion in the distal femoral metaphysis with a Codman triangle. Biopsy confirms high-grade conventional intramedullary osteosarcoma. What is the standard protocol for definitive management?

. Primary amputation followed by radiation therapy
. Neoadjuvant chemotherapy, wide surgical resection, and adjuvant chemotherapy
. Wide surgical resection alone
. Neoadjuvant radiation therapy followed by wide surgical resection
. Excisional biopsy followed by adjuvant radiation therapy

Correct Answer & Explanation

. Neoadjuvant chemotherapy, wide surgical resection, and adjuvant chemotherapy

Explanation

The standard of care for high-grade conventional osteosarcoma includes neoadjuvant chemotherapy, wide surgical resection (limb salvage if possible), and adjuvant chemotherapy. Osteosarcoma is considered highly radioresistant, rendering primary radiation therapy ineffective.

Question 6090

Topic: 10. Pathology and Oncology

A 45-year-old male with a long-standing history of primary synovial chondromatosis of the knee presents with sudden onset of severe rest pain and rapid swelling. Imaging shows bony erosion and a new soft-tissue mass. What is the most likely diagnosis?

. Malignant transformation to chondrosarcoma
. Secondary synovial chondromatosis
. Pigmented villonodular synovitis
. Septic arthritis
. Osteoarthritis progression

Correct Answer & Explanation

. Malignant transformation to chondrosarcoma

Explanation

Rapid clinical deterioration, severe pain, and new bony erosion or soft-tissue mass in a patient with primary synovial chondromatosis strongly suggests malignant transformation to secondary chondrosarcoma, which occurs in up to 5% of cases.

Question 6091

Topic: Bone Tumors
Which of the following mutations is characteristic of McCune-Albright syndrome, a severe systemic form of fibrous dysplasia?
. EXT1 mutation
. GNAS1 mutation
. COL1A1 mutation
. FGFR3 mutation
. COMP mutation

Correct Answer & Explanation

. GNAS1 mutation

Explanation

McCune-Albright syndrome is caused by a somatic activating mutation in the GNAS1 gene, which leads to increased intracellular cAMP, affecting bone, skin (café-au-lait spots), and endocrine tissues.

Question 6092

Topic: Bone Tumors

Radiographs of a 50-year-old man with knee pain show advanced joint space narrowing and multiple intra-articular calcified bodies of varying sizes. Histology shows chondroid nodules with mild cellular atypia. What is the most likely diagnosis?

. Primary synovial chondromatosis
. Secondary synovial chondromatosis
. Chondrosarcoma
. Gouty tophi
. Pigmented villonodular synovitis

Correct Answer & Explanation

. Secondary synovial chondromatosis

Explanation

Secondary synovial chondromatosis is associated with underlying joint pathology like advanced osteoarthritis. The loose bodies typically vary in size and number, unlike primary disease where they are numerous and uniform in size.

Question 6093

Topic: Bone Tumors

A patient with cleidocranial dysplasia presents for orthopedic evaluation. Which of the following skeletal manifestations is most classically associated with this condition?

. Absence or hypoplasia of the clavicles
. Rhizomelic dwarfism
. Severe bowing of the tibiae
. Multiple osteochondromas
. Osteopoikilosis

Correct Answer & Explanation

. Absence or hypoplasia of the clavicles

Explanation

Cleidocranial dysplasia, caused by a RUNX2 (CBFA1) mutation, is characterized by absent or hypoplastic clavicles, delayed closure of cranial sutures, and dental abnormalities.

Question 6094

Topic: Bone Tumors

On T2-weighted MRI, an aneurysmal bone cyst (ABC) is most reliably distinguished from a unicameral bone cyst (UBC) by the presence of which of the following?

. A thin, uniform sclerotic rim
. Fluid-fluid levels with multiple septations
. A purely radiolucent interior without septa
. Extensive perilesional edema
. Cortical thickening

Correct Answer & Explanation

. Fluid-fluid levels with multiple septations

Explanation

While both can occasionally show fluid levels, an ABC typically demonstrates multiple internal septations and distinct fluid-fluid levels on MRI due to the separation of serum and red blood cells in its cystic spaces.

Question 6095

Topic: Bone Tumors

A 10-year-old boy presents with acute arm pain after throwing a baseball. Radiographs reveal a pathologic fracture through a centrally located proximal humerus radiolucent lesion. A small fragment of bone is seen resting at the dependent portion of the lesion. What is the diagnosis?

. Aneurysmal bone cyst
. Non-ossifying fibroma
. Unicameral bone cyst
. Enchondroma
. Chondroblastoma

Correct Answer & Explanation

. Unicameral bone cyst

Explanation

The "fallen leaf" or "fallen fragment" sign is pathognomonic for a pathologic fracture through a unicameral bone cyst (UBC). The cortical fragment breaks off and falls through the fluid-filled cyst to rest at the dependent portion.

Question 6096

Topic: Bone Tumors

An 18-year-old male presents with chronic knee pain. Imaging reveals an eccentrically located, sharply marginated, lobulated radiolucent lesion in the proximal tibial metaphysis with a sclerotic rim. Histology shows stellate cells in a myxoid background with scattered osteoclast-like giant cells. What is the diagnosis?

. Aneurysmal bone cyst
. Chondromyxoid fibroma
. Chondroblastoma
. Unicameral bone cyst
. Giant cell tumor

Correct Answer & Explanation

. Chondromyxoid fibroma

Explanation

The clinical, radiographic (eccentric, lobulated metaphyseal lesion), and histologic (stellate cells in myxoid stroma) features are classic for chondromyxoid fibroma. Chondroblastoma would typically be an epiphyseal lesion.

Question 6097

Topic: Bone Tumors

A 12-year-old boy presents with an eccentric, expansile lytic lesion in the proximal tibia. MRI reveals fluid-fluid levels. Biopsy confirms an Aneurysmal Bone Cyst (ABC). Which of the following genetic abnormalities is most characteristic of this primary lesion?

. GNAS mutation
. USP6 gene rearrangement
. COL2A1 mutation
. EXT1 mutation
. FGFR3 mutation

Correct Answer & Explanation

. USP6 gene rearrangement

Explanation

Primary Aneurysmal Bone Cysts are true neoplasms driven by a recurrent t(16;17) translocation resulting in a USP6 gene rearrangement. GNAS mutations are classically seen in fibrous dysplasia.

Question 6098

Topic: 10. Pathology and Oncology

A 35-year-old male presents with chronic knee pain and locking. Imaging demonstrates over 50 intra-articular loose bodies of uniform size. Pathology shows nodules of hyaline cartilage with mild cellular atypia. What is the primary risk factor for malignant transformation in this condition?

. Total number of loose bodies
. Underlying osteoarthritis
. Presence of the USP6 gene mutation
. Prolonged duration and multiple recurrences
. Extracellular matrix calcification

Correct Answer & Explanation

. Prolonged duration and multiple recurrences

Explanation

Primary synovial chondromatosis has up to a 5% risk of malignant transformation to secondary chondrosarcoma. Risk factors for transformation include long-standing disease and multiple recurrences after synovectomy.

Question 6099

Topic: 10. Pathology and Oncology

A 9-year-old child presents with a pathologic fracture through a proximal humerus lesion. Radiographs show a centrally located lytic lesion with a "fallen leaf" sign. If cyst fluid were aspirated, which of the following biochemical markers would most likely be elevated?

. Alkaline phosphatase
. Prostaglandin E2 (PGE2)
. Interleukin-6 (IL-6)
. Tumor necrosis factor-alpha (TNF-a)
. Fibroblast growth factor 23 (FGF23)

Correct Answer & Explanation

. Prostaglandin E2 (PGE2)

Explanation

Unicameral bone cysts (UBCs) contain serous fluid with markedly elevated levels of Prostaglandin E2 (PGE2) and oxygen free radicals, which stimulate osteoclastic bone resorption. A "fallen leaf" sign is a pathognomonic radiographic feature.

Question 6100

Topic: Bone Tumors
A 25-year-old female presents with an expansile, ground-glass lesion in her proximal femur. She reports a history of precocious puberty and has large, irregular hyperpigmented macules on her back. What is the underlying mechanism of her orthopedic condition?
. Loss-of-function mutation in the NF1 gene
. Activating mutation of the GNAS gene
. Defective carbonic anhydrase II
. Overexpression of the RANKL protein
. Defect in type I collagen synthesis

Correct Answer & Explanation

. Activating mutation of the GNAS gene

Explanation

McCune-Albright syndrome consists of polyostotic fibrous dysplasia, precocious puberty, and café-au-lait spots with "coast of Maine" borders. It is caused by a sporadic, post-zygotic activating mutation in the GNAS gene leading to increased intracellular cAMP.

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