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10. Pathology and Oncology MCQs

Practice Set 222 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 4421

Topic: 10. Pathology and Oncology

A 14-year-old girl is evaluated for a 'shepherd's crook' deformity of her proximal femur. Biopsy reveals irregular woven bone trabeculae lacking osteoblastic rimming set in a bland fibrous stroma. Which of the following gene mutations is most strongly associated with this condition?

. EXT1
. GNAS
. RB1
. PTEN
. FGFR3

Correct Answer & Explanation

. EXT1

Explanation

Fibrous dysplasia is characterized by a missense mutation in the GNAS gene, which encodes the alpha subunit of the stimulatory G protein (Gs). This leads to increased intracellular cAMP, affecting the differentiation of osteoblasts and resulting in the classic 'Chinese character' woven bone trabeculae without osteoblastic rimming in a fibrous stroma.

Question 4422

Topic: 10. Pathology and Oncology

A 24-year-old male presents with anterior lower leg pain. Radiographs show a multicentric, eccentric, lytic lesion in the anterior cortex of the tibial diaphysis. Histopathology reveals clusters of basaloid epithelial cells arranged in nests within a fibrous stroma. What is the most appropriate definitive management?

. Curettage and bone grafting
. Wide surgical resection
. Radiation therapy alone
. Neoadjuvant chemotherapy followed by wide resection
. Observation

Correct Answer & Explanation

. Curettage and bone grafting

Explanation

The clinical, radiographic, and histologic descriptions are classic for adamantinoma. Adamantinoma is a low-grade, malignant bone tumor almost exclusively found in the anterior cortex of the tibial diaphysis. Because it is a sarcoma with metastatic potential and does not typically respond well to chemotherapy or radiation, wide surgical resection with limb reconstruction is the treatment of choice.

Question 4423

Topic: 10. Pathology and Oncology

A 30-year-old female presents with a destructive, expansile lytic lesion in the distal femoral epiphysis. Biopsy confirms a giant cell tumor of bone. Molecular testing of the neoplastic cells is most likely to reveal a mutation in which of the following genes?

. H3F3A
. GNAS
. IDH1
. IDH2
. BRAF

Correct Answer & Explanation

. H3F3A

Explanation

Giant cell tumor of bone (GCTB) is characterized by a high frequency (>90%) of mutations in the H3F3A gene, specifically a G34W mutation. The true neoplastic cells in GCTB are the mononuclear spindle cells, which secrete RANKL to recruit the reactive multinucleated osteoclast-like giant cells.

Question 4424

Topic: 10. Pathology and Oncology

A 25-year-old female presents with a painless posterior knee mass. Radiographs show a densely ossified mass attached to the posterior cortex of the distal femur by a broad base, with a distinct radiolucent cleft separating it from the underlying bone. Genetic analysis of this lesion will most likely demonstrate amplification of which of the following genes?

. C-MYC
. MDM2
. P53
. RB1
. EWSR1

Correct Answer & Explanation

. C-MYC

Explanation

The radiographic description represents a parosteal osteosarcoma, a low-grade surface osteosarcoma that classicly arises on the posterior distal femur. A distinct radiolucent cleft (string sign) often separates it from the cortex. Cytogenetically, parosteal osteosarcoma is characterized by ring chromosomes leading to the amplification of MDM2 and CDK4 on chromosome 12q13-15.

Question 4425

Topic: 10. Pathology and Oncology

A 20-year-old male presents with a painful lytic lesion in the proximal tibial metaphysis. Radiographs show an eccentric, radiolucent defect with a sclerotic margin. Histology demonstrates lobules of stellate and spindle cells in a myxoid stroma, with increased cellularity at the periphery of the lobules. Multinucleated giant cells are present. What is the most likely diagnosis?

. Chondroblastoma
. Chondromyxoid fibroma
. Aneurysmal bone cyst
. Giant cell tumor
. Myxoid liposarcoma

Correct Answer & Explanation

. Chondroblastoma

Explanation

Chondromyxoid fibroma (CMF) is a rare benign bone tumor. Histologically, it is distinctively lobular with hypercellular peripheries and hypocellular, myxoid centers containing stellate or spindle cells. Multinucleated giant cells are frequently found at the lobular peripheries.

Question 4426

Topic: 10. Pathology and Oncology

A 45-year-old man undergoes resection of a large intramuscular mass in his thigh. Pathology reveals a multinodular tumor with a myxoid background, an arborizing 'chicken-wire' capillary network, and small uniform lipoblasts. What chromosomal translocation is diagnostic for this tumor?

. t(X;18)(p11;q11)
. t(11;22)(q24;q12)
. t(12;16)(q13;p11)
. t(2;13)(q35;q14)
. t(9;22)(q22;q12)

Correct Answer & Explanation

. t(X;18)(p11;q11)

Explanation

The histologic description (myxoid background, chicken-wire vasculature, lipoblasts) is classic for myxoid liposarcoma. This tumor is defined by the t(12;16)(q13;p11) translocation, which produces the FUS-DDIT3 fusion protein.

Question 4427

Topic: Bone Tumors

A 68-year-old male with a long history of increasing hat size and bowing of his femurs presents with new, severe mid-thigh pain and a rapidly enlarging mass. Radiographs show a destructive lytic lesion in the bowed femur. What is the most likely histologic finding in the pre-existing bone?

. Thickened trabeculae with a mosaic pattern of prominent cement lines
. Extensive replacement of bone by fibrous tissue lacking osteoblastic rimming
. Thin, osteopenic trabeculae with unmineralized osteoid seams
. Avascular necrosis with empty lacunae
. Cartilage-capped bony exostoses

Correct Answer & Explanation

. Thickened trabeculae with a mosaic pattern of prominent cement lines

Explanation

The patient has secondary osteosarcoma arising in Paget disease of bone. Paget disease is characterized histologically by chaotic bone remodeling resulting in thickened trabeculae with haphazard, intersecting cement lines forming a 'mosaic' or 'jigsaw puzzle' pattern.

Question 4428

Topic: 10. Pathology and Oncology

An 11-year-old boy presents with fever, weight loss, and thigh pain. Radiographs show a permeative, diaphyseal femoral lesion with an 'onion-skin' periosteal reaction. Histology reveals sheets of small, round, blue cells. Which immunohistochemical marker is characteristically strongly positive in this condition?

. S100
. CD99
. MyoD1
. Cytokeratin
. Desmin

Correct Answer & Explanation

. S100

Explanation

Ewing sarcoma is a small round blue cell tumor that typically arises in the diaphysis of long bones. It is strongly associated with the t(11;22) translocation and shows diffuse, strong membranous staining for CD99 (MIC2).

Question 4429

Topic: 10. Pathology and Oncology

A 25-year-old woman is diagnosed with a high-grade bone tumor of the pelvis. Biopsy demonstrates a highly cellular tumor exhibiting a biphasic pattern: sheets of undifferentiated small round blue cells interspersed with distinct, abrupt islands of well-differentiated hyaline cartilage. Hemangiopericytoma-like vascular patterns are also noted. What is the most likely diagnosis?

. Dedifferentiated chondrosarcoma
. Mesenchymal chondrosarcoma
. Clear cell chondrosarcoma
. Ewing sarcoma
. Synovial sarcoma

Correct Answer & Explanation

. Dedifferentiated chondrosarcoma

Explanation

Mesenchymal chondrosarcoma is a rare, highly aggressive tumor characterized by a distinctive biphasic histology consisting of highly cellular areas of primitive, small round blue cells and abrupt islands of well-differentiated, benign-appearing hyaline cartilage. A hemangiopericytoma-like vascular pattern is frequently present.

Question 4430

Topic: Bone Tumors

A 16-year-old boy presents with worsening night pain in his tibia that is dramatically relieved by NSAIDs. Radiographs show a 1 cm radiolucent nidus surrounded by dense reactive sclerosis. If excised, histologic examination of the nidus is most likely to demonstrate which of the following?

. A network of woven bone trabeculae lined by prominent osteoblasts in a highly vascular stroma
. Lobules of hyaline cartilage with scattered binucleated chondrocytes
. Woven bone lacking osteoblastic rimming in a bland fibrous stroma
. Sheets of uniform small blue cells with minimal cytoplasm
. Osteoid production surrounded by highly pleomorphic, hyperchromatic cells

Correct Answer & Explanation

. A network of woven bone trabeculae lined by prominent osteoblasts in a highly vascular stroma

Explanation

The clinical scenario is classic for an osteoid osteoma. Histologically, the nidus of an osteoid osteoma consists of interconnected, disorganized trabeculae of woven bone (osteoid) rimmed by plump, active osteoblasts, set within a highly vascular connective tissue stroma containing numerous nerve fibers (which mediate the intense pain via prostaglandins).

Question 4431

Topic: 10. Pathology and Oncology

A 14-year-old boy presents with a rapidly growing soft tissue mass in his forearm. Biopsy reveals small round blue cells arranged in clusters divided by fibrous septa, forming pseudoalveolar spaces. Cytogenetics identifies a t(2;13) chromosomal translocation. This translocation results in the fusion of which two genes?

. EWS and FLI1
. SYT and SSX1
. PAX3 and FOXO1
. TLS and CHOP
. COL1A1 and PDGFB

Correct Answer & Explanation

. EWS and FLI1

Explanation

The diagnosis is alveolar rhabdomyosarcoma. The characteristic translocation is t(2;13)(q35;q14), which creates the PAX3-FOXO1 (formerly PAX3-FKHR) fusion gene, portending a worse prognosis compared to embryonal rhabdomyosarcoma.

Question 4432

Topic: 10. Pathology and Oncology

A 12-year-old girl presents with a painful, rapidly expanding mass in the posterior elements of her cervical spine. Radiographs reveal an expansile, multicystic lesion. Biopsy shows blood-filled spaces lacking endothelial lining, separated by fibrous septa containing osteoclast-like giant cells. Which of the following genetic alterations is diagnostic of the primary form of this lesion?

. GNAS mutation
. USP6 gene rearrangement
. H3F3A mutation
. MDM2 amplification
. EXT1 mutation

Correct Answer & Explanation

. GNAS mutation

Explanation

The lesion is an aneurysmal bone cyst (ABC). While ABCs can be secondary to other tumors (e.g., GCT, chondroblastoma), primary ABCs are true neoplasms characterized by a balanced translocation resulting in USP6 gene rearrangement (most commonly t(16;17)).

Question 4433

Topic: 10. Pathology and Oncology

A 60-year-old male presents with bowel and bladder incontinence and chronic lower back pain. Imaging shows a large, destructive midline mass involving the sacrum. Biopsy reveals lobules of large cells with prominent intracytoplasmic vacuoles in a myxoid background. Which immunohistochemical marker is highly sensitive and specific for confirming this diagnosis?

. Cytokeratin 7
. S100
. Brachyury
. CD99
. CD34

Correct Answer & Explanation

. Cytokeratin 7

Explanation

The clinical and histologic findings (physaliferous cells with large intracytoplasmic vacuoles) point to a chordoma, a primary bone tumor arising from notochordal remnants. Brachyury, a transcription factor crucial in notochord development, is a highly specific and sensitive immunohistochemical marker for chordoma.

Question 4434

Topic: 10. Pathology and Oncology

A 28-year-old female presents with a lytic lesion in her distal radius. Biopsy demonstrates uniform, spindle-shaped fibroblasts separated by abundant collagenous matrix, without cytologic atypia, pleomorphism, or mitosis. Immunohistochemistry reveals nuclear positivity for beta-catenin. What is the most likely diagnosis?

. Non-ossifying fibroma
. Fibrosarcoma of bone
. Desmoplastic fibroma
. Chondromyxoid fibroma
. Fibrous dysplasia

Correct Answer & Explanation

. Non-ossifying fibroma

Explanation

Desmoplastic fibroma is the rare intraosseous equivalent of a soft-tissue desmoid tumor (aggressive fibromatosis). Like desmoid tumors, it features uniform fibroblasts in a dense collagenous background without overt malignant features, and it typically exhibits aberrant nuclear expression of beta-catenin due to mutations in the Wnt/beta-catenin pathway.

Question 4435

Topic: 10. Pathology and Oncology

A 24-year-old male presents with a painless, slow-growing nodule on the volar aspect of his index finger. Initial excision was read as a necrotizing granuloma, but the mass recurred locally. Re-evaluation of the histology shows nodules of plump epithelioid cells surrounding central areas of necrosis. Immunohistochemistry shows loss of SMARCB1 (INI1) expression. What is the diagnosis?

. Giant cell tumor of tendon sheath
. Synovial sarcoma
. Epithelioid sarcoma
. Nodular fasciitis
. Clear cell sarcoma

Correct Answer & Explanation

. Giant cell tumor of tendon sheath

Explanation

Epithelioid sarcoma often presents in the distal extremities of young adults. Because it forms nodules with central necrosis, it is notoriously misdiagnosed as a benign necrotizing granulomatous process (e.g., rheumatoid nodule). A classic molecular hallmark is the loss of INI1 (SMARCB1) protein expression.

Question 4436

Topic: 10. Pathology and Oncology

A 25-year-old male presents with chronic leg pain. Radiographs reveal a 'soap-bubble' multiloculated osteolytic lesion in the anterior tibial diaphysis. Biopsy reveals islands of epithelial cells surrounded by a bland fibrous stroma. Immunohistochemistry is strongly positive for cytokeratin. Which of the following is the most appropriate management for this condition?

. Intralesional curettage and bone grafting
. Radiation therapy followed by curettage
. Neoadjuvant chemotherapy and wide local excision
. Wide surgical resection
. Primary amputation

Correct Answer & Explanation

. Intralesional curettage and bone grafting

Explanation

The clinical and histologic presentation is classic for Adamantinoma, a rare, low-grade malignant bone tumor that almost exclusively occurs in the anterior tibial diaphysis. Histologically, it features nests of epithelial cells in a fibrous stroma and is cytokeratin positive. It is insensitive to radiation and chemotherapy. The treatment of choice is wide surgical resection with negative margins, often requiring intercalary reconstruction.

Question 4437

Topic: 10. Pathology and Oncology

A 55-year-old male presents with constipation and lower back pain. Imaging shows a large, destructive midline sacral mass. Biopsy reveals lobules of cells with prominent vacuolated cytoplasm in a myxoid background. To differentiate this lesion from a chondrosarcoma, which of the following immunohistochemical markers is the most specific?

. S-100
. Vimentin
. Brachyury
. Epithelial Membrane Antigen (EMA)
. Cytokeratin

Correct Answer & Explanation

. S-100

Explanation

The presentation describes a chordoma, classically located in the sacrococcygeal region or spheno-occipital area (clivus). The cells with vacuolated cytoplasm are 'physaliferous' cells. While chordomas are positive for S-100, cytokeratin, and EMA (which helps distinguish them from chondrosarcomas that are cytokeratin negative), Brachyury—a transcription factor essential for notochordal development—is the most sensitive and highly specific diagnostic nuclear marker for chordoma.

Question 4438

Topic: 10. Pathology and Oncology

A 15-year-old boy presents with knee pain. Radiographs reveal a well-circumscribed, eccentrically located radiolucent lesion in the proximal tibial epiphysis. Biopsy demonstrates mononuclear cells with longitudinal nuclear grooves and areas of fine, intercellular 'chicken-wire' calcifications. Which of the following gene mutations is most characteristically associated with this tumor?

. EXT1
. GNAS
. H3F3A
. IDH1
. TP53

Correct Answer & Explanation

. EXT1

Explanation

The patient has a chondroblastoma, typically occurring in the epiphysis or apophysis of long bones in skeletally immature patients. Histology shows chondroblasts with 'coffee bean' (grooved) nuclei and 'chicken-wire' calcifications. Over 90% of chondroblastomas harbor a somatic mutation in the histone H3.3 genes, most commonly H3F3A (or H3F3B), specifically the K36M substitution.

Question 4439

Topic: 10. Pathology and Oncology

A 45-year-old male presents with progressive hip pain. Radiographs show a distinct, heavily calcified radiolucent lesion in the proximal femoral epiphysis. Biopsy reveals large cells with distinct borders, central round nuclei, and abundant optically clear cytoplasm, mixed with areas of conventional chondrosarcoma and reactive woven bone. What is the most likely diagnosis?

. Chondroblastoma
. Clear cell chondrosarcoma
. Giant cell tumor of bone
. Chondromyxoid fibroma
. Osteoblastoma

Correct Answer & Explanation

. Chondroblastoma

Explanation

Clear cell chondrosarcoma is a rare, low-grade variant of chondrosarcoma that characteristically arises in the epiphysis of long bones (most commonly the proximal femur or humerus) in adults (typically 3rd to 5th decades). Radiographically, it can mimic a chondroblastoma, but chondroblastoma occurs almost exclusively in skeletally immature patients (teens). The histology described is diagnostic of clear cell chondrosarcoma.

Question 4440

Topic: 10. Pathology and Oncology

A 35-year-old woman with recurrent, extensive pigmented villonodular synovitis (PVNS) of the knee is deemed unsuitable for further surgical resection. Systemic medical therapy is planned. This therapy most likely targets which of the following pathways?

. RANK ligand inhibition
. Vascular endothelial growth factor (VEGF) inhibition
. Tyrosine kinase inhibition targeting BCR-ABL
. Colony-stimulating factor 1 receptor (CSF1R) inhibition
. Mammalian target of rapamycin (mTOR) inhibition

Correct Answer & Explanation

. RANK ligand inhibition

Explanation

PVNS (also known as tenosynovial giant cell tumor) is driven by a t(1;2)(p13;q37) translocation, resulting in the fusion of COL6A3 to CSF1. This causes overproduction of Colony-Stimulating Factor 1 (CSF1), which attracts a large non-neoplastic infiltrate of macrophages and multinucleated giant cells. Pexidartinib is a CSF1R inhibitor that has been FDA-approved for adults with symptomatic, locally advanced TGCT associated with severe morbidity or functional limitations that are not amenable to improvement with surgery.

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