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10. Pathology and Oncology MCQs

Practice Set 298 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 5941

Topic: 10. Pathology and Oncology

A 14-year-old boy undergoes neoadjuvant chemotherapy followed by wide surgical resection for conventional osteosarcoma of the distal femur. Which of the following is the most important independent prognostic factor for his overall survival?

. Tumor size at the time of initial presentation
. Histologic response to neoadjuvant chemotherapy
. Serum alkaline phosphatase levels post-resection
. Distance of the tumor from the articular surface
. Presence of a Codman's triangle on initial radiographs

Correct Answer & Explanation

. Histologic response to neoadjuvant chemotherapy

Explanation

The most important prognostic factor for conventional osteosarcoma is the histologic response to neoadjuvant chemotherapy. Tumor necrosis of 90% or greater is considered a good response and correlates strongly with improved survival rates.

Question 5942

Topic: 10. Pathology and Oncology

A 10-year-old child presents with multiple bony prominences. Genetic testing reveals a mutation in the EXT1 gene. The normal product of this gene is primarily involved in which of the following cellular processes?

. Collagen cross-linking
. p53 tumor suppressor pathway regulation
. Fibroblast growth factor receptor signaling
. Heparan sulfate glycosyltransferase activity
. Intracellular calcium transport

Correct Answer & Explanation

. Heparan sulfate glycosyltransferase activity

Explanation

The EXT1 and EXT2 genes encode for glycosyltransferases involved in the synthesis of heparan sulfate. Mutations in these genes lead to Hereditary Multiple Exostoses (HME), disrupting chondrocyte regulation at the growth plate.

Question 5943

Topic: 10. Pathology and Oncology

A 55-year-old man presents with a slow-growing, deep thigh mass. Biopsy demonstrates mature adipocytes with focal areas of atypical, hyperchromatic stromal cells. Fluorescence in situ hybridization (FISH) is most likely to show amplification of which of the following?

. EWS-FLI1
. SYT-SSX
. MDM2 and CDK4
. C-MYC
. TP53

Correct Answer & Explanation

. MDM2 and CDK4

Explanation

Atypical lipomatous tumors (well-differentiated liposarcomas) are characterized by ring or giant marker chromosomes containing amplified sequences of MDM2 and CDK4. This distinguishes them from benign lipomas, which lack this amplification.

Question 5944

Topic: 10. Pathology and Oncology

A 28-year-old woman presents with a slow-growing mass on the posterior aspect of her distal femur. Radiographs reveal a heavily ossified, lobulated mass arising from the surface of the bone with a broad base. Which of the following is characteristic of this lesion?

. It originates in the medullary canal and breaks through the cortex
. It has a higher rate of systemic metastasis than conventional osteosarcoma
. It typically demonstrates MDM2 gene amplification
. It is primarily composed of small round blue cells
. It responds exceptionally well to radiation therapy

Correct Answer & Explanation

. It typically demonstrates MDM2 gene amplification

Explanation

This describes parosteal osteosarcoma, a low-grade surface osteosarcoma typically found on the posterior distal femur. It is characterized molecularly by ring chromosomes with MDM2 and CDK4 amplification.

Question 5945

Topic: 10. Pathology and Oncology

A 16-year-old boy presents with knee pain. Radiographs show a purely lytic, destructive lesion of the distal femur. MRI demonstrates fluid-fluid levels. Biopsy reveals blood-filled spaces with highly pleomorphic, anaplastic cells in the septa producing osteoid. What is the most likely diagnosis?

. Aneurysmal bone cyst
. Unicameral bone cyst
. Telangiectatic osteosarcoma
. Giant cell tumor of bone
. Chondroblastoma

Correct Answer & Explanation

. Telangiectatic osteosarcoma

Explanation

Telangiectatic osteosarcoma mimics an aneurysmal bone cyst radiographically with fluid-fluid levels, but biopsy reveals high-grade sarcomatous cells and malignant osteoid in the septa. ABC septa contain benign fibroblasts and giant cells.

Question 5946

Topic: 10. Pathology and Oncology

A 35-year-old man with Hereditary Multiple Exostoses (HME) notices a rapid increase in the size of a long-standing pelvic mass. Which of the following MRI findings is most indicative of malignant transformation to secondary chondrosarcoma?

. Cartilage cap thickness of 1.0 cm
. Cartilage cap thickness of greater than 2.0 cm
. Presence of marrow continuity with the host bone
. Location in the appendicular skeleton
. A uniform layer of hyaline cartilage

Correct Answer & Explanation

. Cartilage cap thickness of greater than 2.0 cm

Explanation

In adults, a cartilage cap thicker than 2 cm on T2-weighted MRI is highly suspicious for malignant transformation to a secondary peripheral chondrosarcoma. Marrow continuity is a normal feature of a benign osteochondroma.

Question 5947

Topic: 10. Pathology and Oncology

A 45-year-old woman undergoes ankle radiographs for a sprain, revealing an incidental, well-circumscribed radiolucent lesion in the calcaneus with central calcification. What is the most likely diagnosis?

. Chondroblastoma
. Unicameral bone cyst
. Intraosseous lipoma
. Osteoblastoma
. Aneurysmal bone cyst

Correct Answer & Explanation

. Intraosseous lipoma

Explanation

An intraosseous lipoma typically presents as a radiolucent lesion with a central target-like calcification, most commonly in the calcaneus or intertrochanteric region of the femur. It is benign and usually requires no treatment.

Question 5948

Topic: 10. Pathology and Oncology

A 30-year-old man presents with a slow-growing, painless mass in his thigh. MRI shows a lipomatous tumor with prominent vascularity. PET scan demonstrates extremely high FDG avidity. Biopsy reveals multivacuolated fat cells with eosinophilic granular cytoplasm. What is the diagnosis?

. Myxoid liposarcoma
. Pleomorphic liposarcoma
. Hibernoma
. Spindle cell lipoma
. Angiolipoma

Correct Answer & Explanation

. Hibernoma

Explanation

Hibernomas are benign tumors of brown fat characterized by multivacuolated cells with granular cytoplasm. They are highly vascular and demonstrate intense uptake on PET scans, mimicking high-grade sarcomas.

Question 5949

Topic: Bone Tumors

A 15-year-old girl is diagnosed with a high-grade conventional osteosarcoma of the proximal tibia. What is the most appropriate imaging modality to evaluate for the presence of skip metastases within the affected limb?

. CT scan of the lower extremity with IV contrast
. Technetium-99m bone scan
. MRI of the entire tibia and femur
. Ultrasound of the popliteal fossa
. Plain radiographs of the entire lower extremity

Correct Answer & Explanation

. MRI of the entire tibia and femur

Explanation

MRI of the entire affected bone (and adjacent joints) is the gold standard for detecting skip metastases in osteosarcoma. Finding a skip lesion upgrades the staging and alters surgical margins.

Question 5950

Topic: Bone Tumors

Which of the following bone surface tumors is typically a high-grade lesion that shares the same prognosis and treatment protocol as conventional intramedullary osteosarcoma?

. Parosteal osteosarcoma
. Periosteal osteosarcoma
. High-grade surface osteosarcoma
. Osteochondroma
. Periosteal chondroma

Correct Answer & Explanation

. High-grade surface osteosarcoma

Explanation

High-grade surface osteosarcoma is the least common of the surface osteosarcomas but behaves identically to conventional intramedullary osteosarcoma. It requires neoadjuvant chemotherapy and wide resection.

Question 5951

Topic: Bone Tumors

Which of the following is the radiographic hallmark required for the definitive diagnosis of an osteochondroma?

. A stippled calcification pattern within the soft tissues
. Direct continuity of the medullary canal and cortex with the underlying bone
. A solid periosteal reaction with a Codman's triangle
. Presence of a sclerotic rim surrounding a lytic nidus
. MDM2 gene amplification on fluorescent in situ hybridization

Correct Answer & Explanation

. Direct continuity of the medullary canal and cortex with the underlying bone

Explanation

The pathognomonic feature of an osteochondroma is the continuity of both the cortical bone and the medullary canal of the lesion with that of the host bone. This distinguishes it from parosteal surface lesions.

Question 5952

Topic: 10. Pathology and Oncology

A 45-year-old man presents with a palpable mass in the proximal, lateral aspect of his forearm and weakness in extending his fingers. Radiographs show a radiolucent soft tissue mass causing focal hyperostosis of the underlying proximal radius. What is the most likely diagnosis?

. Osteosarcoma compressing the median nerve
. Parosteal lipoma compressing the posterior interosseous nerve
. Periosteal chondroma compressing the superficial radial nerve
. Aneurysmal bone cyst compressing the ulnar nerve
. Giant cell tumor of the tendon sheath

Correct Answer & Explanation

. Parosteal lipoma compressing the posterior interosseous nerve

Explanation

Parosteal lipomas are benign fatty tumors located on the periosteal surface of bones, often causing cortical hyperostosis. In the proximal radius, they frequently cause posterior interosseous nerve (PIN) palsy.

Question 5953

Topic: 10. Pathology and Oncology

A 12-year-old boy with a family history of early-onset breast cancer and adrenocortical carcinoma is diagnosed with osteosarcoma. Which of the following genetic mutations is most likely responsible for this patient's condition?

. RB1
. EXT1
. TP53
. GNAS
. APC

Correct Answer & Explanation

. TP53

Explanation

This clinical picture describes Li-Fraumeni syndrome, an autosomal dominant disorder caused by a germline mutation in the TP53 tumor suppressor gene. It is strongly associated with an increased risk of developing osteosarcoma.

Question 5954

Topic: 10. Pathology and Oncology

Regarding the clinical behavior of atypical lipomatous tumors (ALT) / well-differentiated liposarcomas of the extremity, which of the following statements is true?

. They have a high rate of lymph node metastasis
. They frequently metastasize to the lungs without histologic change
. They have zero potential for distant metastasis unless dedifferentiation occurs
. They require systemic adjuvant chemotherapy routinely
. They invariably resolve following radiation therapy alone

Correct Answer & Explanation

. They have zero potential for distant metastasis unless dedifferentiation occurs

Explanation

Atypical lipomatous tumors (ALTs) are locally aggressive but do not possess the biological capacity to metastasize unless they undergo dedifferentiation into a higher-grade sarcoma (dedifferentiated liposarcoma).

Question 5955

Topic: 10. Pathology and Oncology

A 72-year-old man with a long history of Paget's disease presents with a sudden, severe increase in left thigh pain and a new palpable mass. Radiographs show a destructive lytic lesion with cortical breakthrough. What is the most likely diagnosis?

. Multiple myeloma
. Metastatic prostate carcinoma
. Secondary osteosarcoma
. Chondrosarcoma
. Giant cell tumor of bone

Correct Answer & Explanation

. Secondary osteosarcoma

Explanation

A sudden increase in pain and a new destructive lesion in an older patient with Paget's disease of bone is highly suspicious for malignant transformation to secondary osteosarcoma. This carries a very poor prognosis.

Question 5956

Topic: 10. Pathology and Oncology

A 16-year-old boy with a known osteochondroma of the posterior distal femur presents with a newly enlarging, pulsatile mass behind the knee and decreased distal pulses. What is the most likely complication that has occurred?

. Malignant transformation to chondrosarcoma
. Pathologic fracture through the stalk
. Popliteal artery pseudoaneurysm
. Deep vein thrombosis
. Bursa formation and infection

Correct Answer & Explanation

. Popliteal artery pseudoaneurysm

Explanation

Osteochondromas located near the knee (especially posterior distal femur) can mechanically abrade the popliteal artery, leading to the formation of a pseudoaneurysm. This requires urgent vascular evaluation.

Question 5957

Topic: Bone Tumors

Which of the following chemotherapy agents are considered the standard first-line neoadjuvant regimen for conventional high-grade osteosarcoma?

. Vincristine, Doxorubicin, and Cyclophosphamide
. Methotrexate, Doxorubicin, and Cisplatin
. Ifosfamide and Etoposide
. Imatinib and Sunitinib
. Paclitaxel and Carboplatin

Correct Answer & Explanation

. Methotrexate, Doxorubicin, and Cisplatin

Explanation

The standard MAP regimen for osteosarcoma consists of high-dose Methotrexate, Adriamycin (Doxorubicin), and Platin (Cisplatin). This neoadjuvant treatment is followed by wide surgical resection.

Question 5958

Topic: 10. Pathology and Oncology

Patients with Hereditary Multiple Exostoses (HME) are at risk for malignant transformation to chondrosarcoma. Which genotype has been linked to a higher risk of malignant transformation and more severe disease burden?

. EXT1 mutation
. EXT2 mutation
. EXT3 mutation
. MDM2 amplification
. TP53 mutation

Correct Answer & Explanation

. EXT1 mutation

Explanation

Mutations in the EXT1 gene are generally associated with a higher disease burden, a greater number of exostoses, more severe deformities, and a higher risk of malignant transformation to chondrosarcoma compared to EXT2 mutations.

Question 5959

Topic: 10. Pathology and Oncology

When evaluating a deep soft tissue fatty mass on MRI, which of the following features is most reliable for differentiating an atypical lipomatous tumor from a benign lipoma?

. Presence of a thin, incomplete capsule
. Thickened, nodular septations greater than 2 mm that enhance with contrast
. Location in the subcutaneous fat layer
. Complete suppression on STIR sequencing
. Tumor size less than 5 cm

Correct Answer & Explanation

. Thickened, nodular septations greater than 2 mm that enhance with contrast

Explanation

Atypical lipomatous tumors characteristically show thickened (>2 mm), nodular septations and non-fatty components that enhance on MRI. Benign lipomas typically have thin septa and lack nodular enhancement.

Question 5960

Topic: 10. Pathology and Oncology

Which of the following genetic mutations and corresponding molecular mechanisms are primarily responsible for the development of Hereditary Multiple Exostoses (HME)?

. Gain-of-function mutation in FGFR3 leading to abnormal endochondral ossification
. Loss-of-function mutation in EXT1 or EXT2 causing deficient heparan sulfate synthesis
. Amplification of MDM2 resulting in p53 degradation
. Mutation in GNAS1 leading to constitutive cAMP activation
. Translocation t(11;22) resulting in EWS-FLI1 fusion protein

Correct Answer & Explanation

. Loss-of-function mutation in EXT1 or EXT2 causing deficient heparan sulfate synthesis

Explanation

HME is an autosomal dominant disorder caused by mutations in the EXT1 or EXT2 tumor suppressor genes. These genes encode glycosyltransferases essential for heparan sulfate synthesis, and their deficiency disrupts physeal signaling (e.g., Indian Hedgehog), leading to osteochondroma formation.

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