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10. Pathology and Oncology MCQs

Practice Set 16 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 301

Topic: 10. Pathology and Oncology

Which of the following bone tumors is histologically identical to soft tissue fibromatosis and is considered its intraosseous counterpart?

. Non-ossifying fibroma
. Chondromyxoid fibroma
. Desmoplastic fibroma
. Fibrous dysplasia
. Osteofibrous dysplasia

Correct Answer & Explanation

. Desmoplastic fibroma

Explanation

Desmoplastic fibroma of bone is a rare, locally aggressive benign tumor that is histologically indistinguishable from extra-abdominal soft tissue desmoid tumors. It lacks metastatic potential but exhibits a high rate of local recurrence if managed with simple curettage alone.

Question 302

Topic: Bone Tumors

Percutaneous CT-guided radiofrequency ablation (RFA) is currently considered the gold standard, first-line intervention for which of the following symptomatic lesions?

. Chondroblastoma
. Osteoid osteoma
. Enchondroma
. Aneurysmal bone cyst
. Osteoblastoma larger than 4 cm

Correct Answer & Explanation

. Osteoid osteoma

Explanation

CT-guided radiofrequency ablation (RFA) provides excellent clinical success rates for symptomatic osteoid osteomas. It has largely replaced traditional surgical en bloc resection due to lower morbidity and faster patient recovery.

Question 303

Topic: 10. Pathology and Oncology

A 55-year-old male presents with a large, destructive sacral mass causing bowel and bladder dysfunction. Biopsy reveals large cells with prominent intracytoplasmic vacuoles. Which immunohistochemical marker is highly specific for confirming the suspected diagnosis?

. Brachyury
. S-100
. CD99
. Smooth muscle actin
. Cytokeratin

Correct Answer & Explanation

. Brachyury

Explanation

Chordomas arise from embryonic notochord remnants and contain characteristic physaliferous cells with large vacuoles. Brachyury is a transcription factor crucial for notochord development and acts as a highly sensitive and specific diagnostic marker for chordoma.

Question 304

Topic: 10. Pathology and Oncology

A 14-year-old boy presents with an expansile, eccentric lytic lesion in the proximal tibia. Biopsy reveals blood-filled spaces separated by fibrous septa. Which of the following genetic translocations is most characteristic of this lesion?

. t(11;22)
. t(X;18)
. t(16;17)
. t(12;16)
. t(2;13)

Correct Answer & Explanation

. t(16;17)

Explanation

Primary aneurysmal bone cysts are characterized by a t(16;17) translocation, resulting in the upregulation of USP6. t(11;22) is seen in Ewing sarcoma, while t(X;18) is associated with synovial sarcoma.

Question 305

Topic: 10. Pathology and Oncology

A 16-year-old girl is undergoing surgical resection of a conventional osteosarcoma of the distal femur following neoadjuvant chemotherapy. Which of the following is the most important prognostic factor for her long-term survival?

. Initial tumor volume
. Percentage of tumor necrosis found in the resection specimen
. Presence of a p53 mutation
. Alkaline phosphatase level at initial presentation
. Surgical margins achieved during resection

Correct Answer & Explanation

. Percentage of tumor necrosis found in the resection specimen

Explanation

The percentage of tumor necrosis following neoadjuvant chemotherapy is the most reliable prognostic indicator for long-term survival in conventional osteosarcoma. Greater than 90% necrosis is considered a good histologic response.

Question 306

Topic: Bone Tumors

A 9-year-old girl is diagnosed with polyostotic fibrous dysplasia, precocious puberty, and cafe-au-lait spots. The pathophysiology of her condition is directly related to a mutation in which of the following?

. Gs-alpha protein (GNAS1 gene)
. Fibroblast growth factor receptor 3 (FGFR3)
. Collagen type I alpha 1 chain (COL1A1)
. EXT1 tumor suppressor gene
. Retinoblastoma (Rb) gene

Correct Answer & Explanation

. Gs-alpha protein (GNAS1 gene)

Explanation

McCune-Albright syndrome features polyostotic fibrous dysplasia, endocrine abnormalities, and cafe-au-lait spots. It is caused by a somatic, post-zygotic activating mutation in the GNAS1 gene, resulting in elevated intracellular cAMP.

Question 307

Topic: Bone Tumors

A 65-year-old man presents with a rapidly enlarging mass in his proximal femur. Radiographs demonstrate a pre-existing lesion with rings-and-arcs calcification and a new, large, aggressive unmineralized soft tissue mass. Which of the following is the most likely diagnosis?

. Clear cell chondrosarcoma
. Mesenchymal chondrosarcoma
. Dedifferentiated chondrosarcoma
. Secondary osteosarcoma
. Primary lymphoma of bone

Correct Answer & Explanation

. Dedifferentiated chondrosarcoma

Explanation

A bimorphic radiographic appearance (a low-grade cartilaginous lesion adjacent to a high-grade, unmineralized soft-tissue mass) is pathognomonic for dedifferentiated chondrosarcoma. This transformation carries a very poor prognosis.

Question 308

Topic: 10. Pathology and Oncology

A 12-year-old boy presents with multiple enchondromas and multiple soft-tissue hemangiomas. Which of the following complications is he at the highest risk of developing over his lifetime?

. Osteosarcoma
. Leukemia
. Chondrosarcoma
. Angiosarcoma
. Gastrointestinal stromal tumor (GIST)

Correct Answer & Explanation

. Chondrosarcoma

Explanation

Maffucci syndrome is characterized by multiple enchondromas and soft-tissue hemangiomas. Patients have a nearly 100% lifetime risk of malignant transformation, most commonly to chondrosarcoma, but also visceral malignancies.

Question 309

Topic: 10. Pathology and Oncology

A 10-year-old boy presents with an aggressive diaphyseal lesion of the femur with an "onion skin" periosteal reaction. Immunohistochemical staining of the biopsy specimen is most likely to be positive for which of the following markers?

. S-100
. CD99
. Cytokeratin
. MyoD1
. Desmin

Correct Answer & Explanation

. CD99

Explanation

Ewing sarcoma is a small round blue cell tumor typically found in the diaphysis of long bones in children. It strongly stains positive for CD99 (MIC2) and usually harbors a t(11;22) translocation.

Question 310

Topic: Bone Tumors

A 14-year-old male with multiple hereditary exostoses (MHE) is evaluated. The genetic mutation associated with his condition leads to a deficiency in the synthesis of which of the following?

. Hyaluronic acid
. Heparan sulfate
. Chondroitin sulfate
. Keratan sulfate
. Dermatan sulfate

Correct Answer & Explanation

. Heparan sulfate

Explanation

MHE is an autosomal dominant condition caused by mutations in the EXT1 or EXT2 genes. These genes encode glycosyltransferases essential for the synthesis of heparan sulfate, leading to abnormal physeal signaling and osteochondroma formation.

Question 311

Topic: 10. Pathology and Oncology

A 12-year-old boy presents with a rapidly expanding, painful lytic lesion in the distal femur. Biopsy reveals blood-filled cystic spaces lacking an endothelial lining. Which of the following genetic translocations is most characteristic of this primary lesion?

. t(16;17) USP6
. t(11;22) EWS-FLI1
. t(X;18) SYT-SSX
. t(12;16) FUS-CHOP
. t(17;22) COL1A1-PDGFB

Correct Answer & Explanation

. t(16;17) USP6

Explanation

Primary aneurysmal bone cysts (ABCs) are neoplastic and characterized by the t(16;17) translocation involving the USP6 gene. The other translocations are associated with Ewing sarcoma, Synovial sarcoma, Myxoid liposarcoma, and Dermatofibrosarcoma protuberans, respectively.

Question 312

Topic: 10. Pathology and Oncology

A 15-year-old male presents with a painful, permeative diaphyseal lesion in the femur with a laminated periosteal reaction. Histopathology shows small, round blue cells. Which of the following fusion genes is responsible for the pathogenesis of this condition?

. EWS-FLI1
. EWS-ERG
. PAX3-FKHR
. SYT-SSX
. TLS-CHOP

Correct Answer & Explanation

. EWS-FLI1

Explanation

The patient has Ewing sarcoma, which is characterized by an onionskin periosteal reaction and small round blue cells. Approximately 85% to 90% of Ewing sarcomas express the t(11;22) translocation resulting in the EWS-FLI1 fusion protein.

Question 313

Topic: 10. Pathology and Oncology

A 14-year-old boy complains of chronic knee pain. Radiographs demonstrate a 2-cm lucent lesion with a sclerotic rim located exclusively within the proximal tibial epiphysis. Histological analysis reveals mononuclear cells and "chicken-wire" calcification. What is the location of this tumor relative to the physis?

. Epiphysis
. Metaphysis
. Diaphysis
. Metadiaphysis
. Cortical surface

Correct Answer & Explanation

. Epiphysis

Explanation

Chondroblastoma is a rare benign cartilage tumor that almost exclusively arises in the epiphysis or apophysis of growing children. The pathognomonic histological finding is pericellular "chicken-wire" calcification.

Question 314

Topic: Bone Tumors

An 18-year-old male presents with severe proximal focal tibial pain that worsens at night and is completely relieved by ibuprofen. Imaging reveals a cortically based radiolucent nidus surrounded by dense reactive sclerosis. The pain in this condition is primarily mediated by excessive production of which of the following?

. Interleukin-1
. Interleukin-6
. Prostaglandin E2
. Tumor Necrosis Factor-alpha
. Transforming Growth Factor-beta

Correct Answer & Explanation

. Prostaglandin E2

Explanation

Osteoid osteoma causes severe night pain due to a 100- to 1000-fold increase in local prostaglandin E2 (PGE2) production by the nidus cells. This explains the dramatic clinical response to cyclooxygenase inhibitors like NSAIDs.

Question 315

Topic: Bone Tumors
An 8-year-old girl is evaluated for precocious puberty, café-au-lait macules with irregular "coast of Maine" borders, and a "shepherd's crook" deformity of the proximal femur. This syndrome is caused by a somatic activating mutation in which of the following genes?
. FGFR3
. EXT1
. GNAS
. COMP
. COL1A1

Correct Answer & Explanation

. GNAS

Explanation

McCune-Albright syndrome consists of polyostotic fibrous dysplasia, café-au-lait spots, and endocrinopathies. It is caused by a somatic, post-zygotic activating mutation in the GNAS gene, leading to overproduction of intracellular cAMP.

Question 316

Topic: 10. Pathology and Oncology

A 10-year-old boy is diagnosed with Maffucci syndrome after presenting with multiple enchondromas and soft tissue hemangiomas. Which of the following gene mutations is most strongly associated with this condition?

. P53
. RB1
. IDH1/IDH2
. PTEN
. APC

Correct Answer & Explanation

. IDH1/IDH2

Explanation

Maffucci syndrome and Ollier disease are associated with somatic mosaic mutations in the isocitrate dehydrogenase 1 or 2 (IDH1 or IDH2) genes. Maffucci syndrome carries a significantly higher risk of malignant transformation to chondrosarcoma compared to Ollier disease.

Question 317

Topic: Bone Tumors

A patient with multiple bony protuberances around the knees and shoulders is diagnosed with Multiple Hereditary Exostoses (MHE). Genetic testing confirms a mutation in the EXT1 gene. This mutation directly impairs the synthesis of which of the following cell surface molecules?

. Heparan sulfate
. Chondroitin sulfate
. Hyaluronic acid
. Keratan sulfate
. Dermatan sulfate

Correct Answer & Explanation

. Heparan sulfate

Explanation

The EXT1 and EXT2 genes encode glycosyltransferases essential for the biosynthesis of heparan sulfate. Defective heparan sulfate synthesis alters chondrocyte signaling (such as Indian Hedgehog and PTHrP pathways), leading to the formation of osteochondromas.

Question 318

Topic: 10. Pathology and Oncology

A 16-year-old male is diagnosed with high-grade conventional intramedullary osteosarcoma of the distal femur. Staging studies are performed. What is the single most important prognostic factor for overall survival at the time of initial presentation?

. Tumor size
. Histologic subtype
. Presence of pulmonary metastasis
. Initial alkaline phosphatase level
. Age of the patient

Correct Answer & Explanation

. Presence of pulmonary metastasis

Explanation

In osteosarcoma, the presence of detectable metastatic disease (most commonly to the lungs) at the time of presentation is the most significant adverse prognostic factor. While tumor necrosis following neoadjuvant chemotherapy is an important prognostic factor later, initial staging relies heavily on metastatic status.

Question 319

Topic: 10. Pathology and Oncology

Which of the following genetic translocations is highly characteristic of a primary aneurysmal bone cyst (ABC)?

. t(11;22)(q24;q12)
. t(X;18)(p11;q11)
. t(16;17)(q22;p13)
. t(2;13)(q35;q14)
. t(12;16)(q13;p11)

Correct Answer & Explanation

. t(16;17)(q22;p13)

Explanation

Primary aneurysmal bone cysts are characterized by the t(16;17) translocation which upregulates the USP6 oncogene. In contrast, Ewing sarcoma is associated with t(11;22) and synovial sarcoma with t(X;18).

Question 320

Topic: 10. Pathology and Oncology

A 14-year-old boy presents with knee pain. Radiographs reveal a lytic lesion in the proximal tibial epiphysis. Biopsy shows mononuclear cells with grooved nuclei and areas of pericellular calcification. Which of the following is the most likely diagnosis?

. Giant cell tumor
. Chondroblastoma
. Clear cell chondrosarcoma
. Aneurysmal bone cyst
. Osteomyelitis

Correct Answer & Explanation

. Chondroblastoma

Explanation

Chondroblastoma typically occurs in the epiphysis of skeletally immature patients. Histology demonstrates chondroblasts with "coffee-bean" (grooved) nuclei and characteristic "chicken-wire" pericellular calcification.

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