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10. Pathology and Oncology MCQs

Practice Set 333 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 6641

Topic: Bone Tumors

A 45-year-old asymptomatic woman undergoes knee radiography for mild osteoarthritis. An incidental 3-cm lobulated, calcified metaphyseal lesion is found in the distal femur. MRI demonstrates lobular hyperintensity on T2-weighted images without cortical breakthrough or soft tissue extension. Which genetic mutation is most commonly associated with this specific tumor's pathogenesis?

. EXT1 or EXT2 mutations
. IDH1 or IDH2 mutations
. GNAS1 mutations
. t(11;22) translocation
. p53 mutations

Correct Answer & Explanation

. IDH1 or IDH2 mutations

Explanation

Enchondromas and chondrosarcomas are frequently associated with somatic mutations in isocitrate dehydrogenase 1 and 2 (IDH1/IDH2). EXT mutations are seen in osteochondromas, while GNAS1 is associated with fibrous dysplasia.

Question 6642

Topic: 10. Pathology and Oncology

A 16-year-old boy presents with a painless lump on his proximal humerus. Radiographs reveal a surface lesion causing 'saucerization' of the underlying cortex with a well-defined sclerotic margin and stippled calcifications.

What is the most appropriate initial management for this lesion if it remains asymptomatic?

. Neoadjuvant chemotherapy followed by wide resection
. Wide en bloc resection
. Intralesional curettage and bone grafting
. Observation with serial radiographs
. Immediate incisional biopsy

Correct Answer & Explanation

. Observation with serial radiographs

Explanation

The clinical and radiographic presentation is classic for a periosteal chondroma, a benign surface cartilage tumor. Asymptomatic periosteal chondromas can be managed with observation and serial radiographs.

Question 6643

Topic: 10. Pathology and Oncology

A 30-year-old male with Maffucci syndrome presents with increasing pain in his distal femur. Radiographs show a previously calcified enchondroma that now exhibits cortical destruction and a soft-tissue mass. Which of the following systemic malignancies is this patient at highest risk for compared to a patient with Ollier disease?

. Thyroid carcinoma
. Renal cell carcinoma
. Gastrointestinal adenocarcinoma
. Pulmonary squamous cell carcinoma
. Prostate cancer

Correct Answer & Explanation

. Gastrointestinal adenocarcinoma

Explanation

Maffucci syndrome (multiple enchondromas and soft-tissue hemangiomas) carries an exceptionally high risk of malignant transformation, not only to chondrosarcoma but also to systemic malignancies like gastrointestinal adenocarcinomas and brain tumors (astrocytomas). This distinguishes its systemic risk profile from Ollier disease.

Question 6644

Topic: 10. Pathology and Oncology
A 14-year-old girl is diagnosed with high-grade conventional osteosarcoma of the distal femur. She completes neoadjuvant chemotherapy and undergoes surgical resection. Pathological analysis of the resected specimen reveals 95% tumor necrosis. What is the most significant clinical implication of this finding?
. She does not require adjuvant chemotherapy.
. She has a higher likelihood of long-term event-free survival.
. She is at increased risk for skip metastases.
. The tumor was likely an osteoblastoma rather than osteosarcoma.
. She will require immediate whole-lung irradiation.

Correct Answer & Explanation

. She has a higher likelihood of long-term event-free survival.

Explanation

Tumor necrosis greater than 90% following neoadjuvant chemotherapy (Huvos Grade III or IV) is the most powerful predictor of long-term survival in localized osteosarcoma. Adjuvant chemotherapy is still indicated.

Question 6645

Topic: 10. Pathology and Oncology

Which of the following radiographic features best differentiates a low-grade chondrosarcoma from a benign enchondroma in a long bone?

. Presence of 'rings and arcs' calcifications
. Central, diaphyseal location
. Endosteal scalloping greater than two-thirds of the cortical thickness
. Lobular high signal intensity on T2-weighted MRI
. Intact cortex without periosteal reaction

Correct Answer & Explanation

. Endosteal scalloping greater than two-thirds of the cortical thickness

Explanation

While both enchondromas and low-grade chondrosarcomas exhibit cartilage matrix ('rings and arcs') and high T2 MRI signal, deep endosteal scalloping (>2/3 cortical thickness) is a hallmark of aggressive behavior favoring chondrosarcoma. Pain independent of mechanical causes also strongly suggests malignancy.

Question 6646

Topic: 10. Pathology and Oncology

A 17-year-old male with classic Ewing sarcoma of the diaphyseal femur undergoes initial staging. Which of the following sites is the most common location for metastasis in this disease, and what specific staging test is uniquely mandatory compared to osteosarcoma?

. Liver; abdominal MRI
. Lungs; bone marrow aspirate and biopsy
. Brain; lumbar puncture
. Lymph nodes; sentinel lymph node biopsy
. Spine; whole spine MRI

Correct Answer & Explanation

. Lungs; bone marrow aspirate and biopsy

Explanation

The lungs are the most common site of metastasis for Ewing sarcoma, followed by bone and bone marrow. A bone marrow aspirate and biopsy are mandatory parts of the initial staging for Ewing sarcoma, unlike osteosarcoma.

Question 6647

Topic: 10. Pathology and Oncology

A 65-year-old male with a long-standing, stable calcified lesion in his proximal humerus presents with sudden, rapidly progressive pain and a palpable soft tissue mass. Biopsy reveals a biphasic tumor with regions of low-grade hyaline cartilage adjacent to a high-grade undifferentiated spindle cell sarcoma. What is the diagnosis?

. Mesenchymal chondrosarcoma
. Clear cell chondrosarcoma
. Dedifferentiated chondrosarcoma
. Secondary osteosarcoma
. Chondroblastic osteosarcoma

Correct Answer & Explanation

. Dedifferentiated chondrosarcoma

Explanation

Dedifferentiated chondrosarcoma is characterized by a bimorphic histologic pattern showing a low-grade chondroid tumor abruptly transitioning into a high-grade, non-cartilaginous sarcoma. It carries a very poor prognosis.

Question 6648

Topic: Bone Tumors

A 40-year-old female presents with shoulder pain. Radiographs reveal a purely lytic lesion confined to the epiphysis of the proximal humerus. Histology demonstrates cells with abundant clear cytoplasm, distinct borders, and scattered multinucleated giant cells within a cartilaginous background. What is the most likely diagnosis?

. Conventional chondrosarcoma
. Chondroblastoma
. Clear cell chondrosarcoma
. Enchondroma
. Periosteal chondroma

Correct Answer & Explanation

. Clear cell chondrosarcoma

Explanation

Clear cell chondrosarcoma typically presents as a lytic lesion in the epiphysis of long bones (often proximal femur or humerus) in adults. Chondroblastoma also occurs in the epiphysis but usually in younger, skeletally immature patients.

Question 6649

Topic: 10. Pathology and Oncology
During the surgical planning for a patient with high-grade osteosarcoma of the distal femur, an MRI of the entire femur is obtained. The primary purpose of imaging the entire bone is to evaluate for which of the following?
. Bone marrow edema
. Neurovascular bundle encasement
. Skip metastases
. Joint involvement
. Cortical breakthrough

Correct Answer & Explanation

. Skip metastases

Explanation

Whole-bone MRI is essential in the staging of osteosarcoma and Ewing sarcoma to detect skip metastases (tumors within the same bone separated from the primary lesion by normal marrow). Their presence upgrades the tumor to Stage III and necessitates a broader resection or total bone replacement.

Question 6650

Topic: 10. Pathology and Oncology

A 21-year-old patient who underwent distal femoral replacement for osteosarcoma 2 years ago presents for follow-up. A routine chest CT shows a solitary 1.5 cm peripheral nodule in the right lower lobe. The primary tumor site is free of recurrence, and no other lesions are noted. What is the most appropriate next step in management?

. Hospice care
. Palliative radiation therapy to the lung
. Surgical resection of the pulmonary nodule (metastasectomy)
. Initiation of oral tyrosine kinase inhibitors
. Observation with repeat CT in 6 months

Correct Answer & Explanation

. Surgical resection of the pulmonary nodule (metastasectomy)

Explanation

In osteosarcoma patients with isolated, completely resectable pulmonary metastases and a controlled primary tumor, surgical metastasectomy offers the best chance for prolonged survival and potential cure.

Question 6651

Topic: 10. Pathology and Oncology

A 35-year-old male undergoes a radiograph for knee pain. A surface lesion is noted on the distal femur. Biopsy reveals intermediate-grade malignant cells producing a predominantly cartilaginous matrix with some osteoid, situated on the cortical surface without medullary involvement. The radiographic appearance shows a 'sunburst' periosteal reaction. What is the diagnosis?

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

Correct Answer & Explanation

. Periosteal osteosarcoma

Explanation

Periosteal osteosarcoma is typically an intermediate-grade surface tumor with a chondroblastic matrix, often presenting with a 'sunburst' periosteal reaction. Parosteal osteosarcoma is low-grade, heavily ossified, and typically located on the posterior distal femur.

Question 6652

Topic: 10. Pathology and Oncology

A 50-year-old male presents with a destructive bone lesion in the pelvis. A biopsy is planned. Before performing a biopsy on a suspected metastatic lesion of unknown primary origin, what is the most critical initial diagnostic step?

. Empiric radiation therapy
. Complete staging imaging (CT Chest/Abdomen/Pelvis, Bone Scan)
. Initiation of bisphosphonates
. Prophylactic internal fixation
. Positron emission tomography (PET) of the brain only

Correct Answer & Explanation

. Complete staging imaging (CT Chest/Abdomen/Pelvis, Bone Scan)

Explanation

Before biopsying a suspected metastasis, complete staging is required. This identifies the primary tumor, locates potentially safer or more accessible biopsy sites, and rules out highly vascular tumors (e.g., renal cell or thyroid carcinoma) that require pre-biopsy embolization.

Question 6653

Topic: 10. Pathology and Oncology

An MRI of the knee in a 40-year-old woman shows a medullary lesion in the distal femur. The radiologist notes a 'double-line sign' on T2-weighted images and a serpiginous border, distinguishing it from an enchondroma. What is the most likely diagnosis?

. Bone infarct
. Chondromyxoid fibroma
. Non-ossifying fibroma
. Fibrous dysplasia
. Giant cell tumor

Correct Answer & Explanation

. Bone infarct

Explanation

The 'double-line sign' on T2 MRI (inner high signal of granulation tissue, outer low signal of sclerosis) and a serpiginous border are classic imaging hallmarks of a bone infarct, differentiating it from the lobular hyperintensity of an enchondroma.

Question 6654

Topic: 10. Pathology and Oncology

A 28-year-old man presents with a small, palpable mass on his proximal tibia. Radiographs show a well-circumscribed, saucer-like cortical depression with a sclerotic rim.

Histology shows benign hyaline cartilage. Which characteristic best differentiates this from an osteochondroma?

. Presence of a cartilage cap
. Lack of medullary continuity with the host bone
. Malignant transformation risk greater than 50%
. Location in the epiphysis
. Endosteal scalloping

Correct Answer & Explanation

. Lack of medullary continuity with the host bone

Explanation

Periosteal chondromas are surface lesions that arise under the periosteum and erode the outer cortex (saucerization). Unlike osteochondromas, they do not exhibit continuity with the medullary canal of the host bone.

Question 6655

Topic: 10. Pathology and Oncology

A 30-year-old woman presents with jaw pain. Imaging reveals a destructive lesion in the mandible. Histology displays a biphasic pattern with islands of well-differentiated hyaline cartilage surrounded by sheets of small, undifferentiated round blue cells in a hemangiopericytoma-like vascular pattern. What is the diagnosis?

. Ewing sarcoma
. Dedifferentiated chondrosarcoma
. Mesenchymal chondrosarcoma
. Osteosarcoma
. Chondroblastoma

Correct Answer & Explanation

. Mesenchymal chondrosarcoma

Explanation

Mesenchymal chondrosarcoma features a distinct biphasic histology: islands of benign-appearing cartilage mixed with highly cellular areas of small round blue cells. It frequently occurs in the jaw, ribs, or extraskeletal sites.

Question 6656

Topic: 10. Pathology and Oncology
In a 15-year-old male with osteosarcoma of the proximal tibia, which of the following findings would upstage the patient to Stage III according to the Enneking Surgical Staging System?
. Extension of the tumor into the surrounding soft tissue
. A high histologic grade on biopsy
. Presence of an identical neoplastic lesion in the distal tibia separated by normal marrow
. Pathologic fracture through the primary lesion
. Intra-articular extension into the knee joint

Correct Answer & Explanation

. Presence of an identical neoplastic lesion in the distal tibia separated by normal marrow

Explanation

In the Enneking system, Stage III denotes the presence of regional or distant metastasis. A skip metastasis (a separate tumor nodule within the same bone) is considered a regional metastasis and automatically upgrades the tumor to Stage III.

Question 6657

Topic: 10. Pathology and Oncology

Which of the following bone tumors characteristically expresses the t(11;22)(q24;q12) chromosomal translocation resulting in the EWS-FLI1 fusion protein?

. Osteosarcoma
. Synovial sarcoma
. Ewing sarcoma
. Chondrosarcoma
. Myxoid liposarcoma

Correct Answer & Explanation

. Ewing sarcoma

Explanation

Ewing sarcoma is defined molecularly by the t(11;22) translocation, which fuses the EWSR1 gene on chromosome 22 with the FLI1 gene on chromosome 11. Synovial sarcoma has t(X;18), and myxoid liposarcoma has t(12;16).

Question 6658

Topic: 10. Pathology and Oncology

A patient with multiple hereditary exostoses (MHE) is monitored for malignant transformation. Which clinical or radiographic sign is the most reliable indicator of secondary chondrosarcoma arising from an osteochondroma in an adult?

. Cartilage cap thickness of 5 mm on MRI
. Pain and growth of the lesion after skeletal maturity
. Presence of a stalk pointing away from the joint
. Medullary continuity with the host bone
. Multiple lesions rather than a solitary lesion

Correct Answer & Explanation

. Pain and growth of the lesion after skeletal maturity

Explanation

In an adult (skeletally mature) patient, an osteochondroma should not grow. New-onset pain, growth, or an MRI showing a cartilage cap greater than 1.5 to 2 cm are highly suspicious for malignant transformation to secondary chondrosarcoma.

Question 6659

Topic: 10. Pathology and Oncology

A 20-year-old male undergoes curettage of a lytic lesion in the proximal phalanx of the hand.

Pathological examination shows lobules of mature hyaline cartilage. Which of the following best describes the recurrence risk and malignant potential of this solitary hand lesion?

. High recurrence rate, high malignant potential
. Low recurrence rate, virtually zero malignant potential
. High recurrence rate, moderate malignant potential
. Zero recurrence rate, requires systemic chemotherapy
. Low recurrence rate, high risk of pulmonary metastasis

Correct Answer & Explanation

. Low recurrence rate, virtually zero malignant potential

Explanation

Solitary enchondromas of the hand have a low recurrence rate after adequate intralesional curettage and grafting. Malignant transformation of a solitary enchondroma in the hand is exceedingly rare, distinguishing it from enchondromas in long bones.

Question 6660

Topic: 10. Pathology and Oncology

Which of the following radiographic features is the most reliable indicator differentiating a low-grade central chondrosarcoma from a benign enchondroma in a long bone?

. Presence of calcified cartilaginous matrix
. Lesion size greater than 2 cm
. Endosteal scalloping involving greater than two-thirds of the cortical thickness
. Location in the metaphyseal-diaphyseal junction
. Intramedullary location

Correct Answer & Explanation

. Endosteal scalloping involving greater than two-thirds of the cortical thickness

Explanation

Endosteal scalloping greater than two-thirds of the cortical thickness, cortical breakthrough, or soft tissue extension strongly suggests a low-grade chondrosarcoma rather than a benign enchondroma.

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