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10. Pathology and Oncology MCQs

Practice Set 299 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 5961

Topic: 10. Pathology and Oncology

A 55-year-old male presents with a deep 8 cm soft tissue mass in the anterior thigh. Biopsy shows mature adipocytes with focal atypical cells and thickened fibrous septa. Which genetic aberration definitively distinguishes this Atypical Lipomatous Tumor (ALT) from a benign lipoma?

. Translocation t(X;18)(p11;q11)
. Rearrangement of the HMGA2 gene on 12q14.3
. Amplification of MDM2 and CDK4 on chromosome 12q14-15
. Translocation t(12;16)(q13;p11)
. Mutation in the beta-catenin (CTNNB1) gene

Correct Answer & Explanation

. Amplification of MDM2 and CDK4 on chromosome 12q14-15

Explanation

Atypical Lipomatous Tumors (ALT) and well-differentiated liposarcomas are characterized by the amplification of MDM2 and CDK4 genes on chromosome 12q14-15. Fluorescence in situ hybridization (FISH) for MDM2 is the gold standard diagnostic test to differentiate ALT from benign lipomas.

Question 5962

Topic: 10. Pathology and Oncology
A 16-year-old male with conventional osteosarcoma of the distal femur completes a 10-week course of neoadjuvant MAP (methotrexate, doxorubicin, cisplatin) chemotherapy followed by wide resection. Which histologic finding in the resected specimen is the most critical independent predictor of long-term survival?
. Greater than 90% tumor necrosis
. Presence of a prominent chondroblastic matrix
. Complete peripheral calcification of the tumor capsule
. Absence of MDM2 amplification in the residual cells
. Negative surgical margins > 5 cm

Correct Answer & Explanation

. Greater than 90% tumor necrosis

Explanation

The degree of tumor necrosis following neoadjuvant chemotherapy is the most important prognostic indicator in conventional osteosarcoma. Greater than 90% necrosis (Huvos Grade III or IV) correlates strongly with significantly improved disease-free and overall survival.

Question 5963

Topic: Bone Tumors

A 28-year-old female presents with a painless, slow-growing mass behind her knee. Radiographs reveal a densely ossified, lobulated mass arising from the posterior cortex of the distal femur, separated from the underlying bone by a narrow radiolucent cleft (the "string sign"). What is the most likely diagnosis?

. Periosteal osteosarcoma
. High-grade surface osteosarcoma
. Parosteal osteosarcoma
. Myositis ossificans
. Sessile osteochondroma

Correct Answer & Explanation

. Parosteal osteosarcoma

Explanation

Parosteal osteosarcoma is a low-grade surface malignancy that most frequently arises on the posterior distal femur. It classically presents with dense, mature ossification at its base and a radiolucent cleft separating the tumor from the cortex, known as the 'string sign'.

Question 5964

Topic: Bone Tumors

In a child with Hereditary Multiple Exostoses (HME), what is the most common forearm deformity requiring surgical intervention?

. Relative radial shortening with ulnar bowing
. Relative ulnar shortening with secondary radial bowing
. Proximal radioulnar synostosis
. Volar subluxation of the distal ulna
. Madelung deformity

Correct Answer & Explanation

. Relative ulnar shortening with secondary radial bowing

Explanation

The most common forearm deformity in HME (Masada type I) is caused by a distal ulnar osteochondroma tethering growth, resulting in relative ulnar shortening, secondary radial bowing, and ulnar deviation of the carpus. Without intervention, this can lead to radial head dislocation.

Question 5965

Topic: 10. Pathology and Oncology

A 14-year-old female presents with severe distal thigh pain. MRI reveals a lytic, expansile metaphyseal lesion with prominent fluid-fluid levels. Core needle biopsy demonstrates blood-filled spaces separated by septa containing highly pleomorphic cells producing delicate osteoid. What is the diagnosis?

. Aneurysmal bone cyst (ABC)
. Giant cell tumor of bone
. Telangiectatic osteosarcoma
. Chondroblastoma
. Ewing sarcoma

Correct Answer & Explanation

. Telangiectatic osteosarcoma

Explanation

Telangiectatic osteosarcoma closely mimics an aneurysmal bone cyst (ABC) on imaging due to characteristic fluid-fluid levels. It is differentiated histologically by the presence of highly malignant, pleomorphic mesenchymal cells producing delicate osteoid within the septa.

Question 5966

Topic: Bone Tumors

Which of the following surface osteosarcoma variants is typically intermediate-grade, has a prominent chondroblastic histologic component, and classically presents as a "sunburst" periosteal reaction on the diaphyseal surface without medullary involvement?

. Parosteal osteosarcoma
. Periosteal osteosarcoma
. High-grade surface osteosarcoma
. Secondary osteosarcoma
. Telangiectatic osteosarcoma

Correct Answer & Explanation

. Periosteal osteosarcoma

Explanation

Periosteal osteosarcoma is an intermediate-grade surface tumor predominantly affecting the diaphyseal surface of long bones. It is characteristically chondroblastic, exhibits a 'sunburst' periosteal reaction, and typically lacks medullary canal invasion.

Question 5967

Topic: 10. Pathology and Oncology



A 15-year-old boy presents with the radiographic findings shown. Biopsy confirms conventional osteosarcoma. What is the most common initial site of metastasis for this disease?

. Spine
. Brain
. Liver
. Lungs
. Regional lymph nodes

Correct Answer & Explanation

. Lungs

Explanation

Conventional osteosarcoma most frequently metastasizes to the lungs, which is the primary cause of mortality in these patients. Routine staging must always include a high-resolution CT of the chest to assess for pulmonary nodules.

Question 5968

Topic: 10. Pathology and Oncology

An asymptomatic 60-year-old male has a 12 cm intramuscular lipomatous mass in his anterior thigh. Core biopsy confirms Atypical Lipomatous Tumor (ALT). What is the most appropriate surgical management for this extremity lesion?

. Intralesional curettage with adjuvant phenol
. Marginal excision
. Wide local excision with 5 cm margins
. Neoadjuvant radiation followed by wide excision
. Amputation

Correct Answer & Explanation

. Marginal excision

Explanation

ALTs occurring in the extremities have virtually zero metastatic potential but a high rate of local recurrence. Marginal excision is the recommended treatment to preserve limb function, as extensive wide resection does not alter overall survival.

Question 5969

Topic: 10. Pathology and Oncology

A 25-year-old female presents with a painless mass behind her knee. Radiographs reveal a densely ossified mass attached to the posterior cortex of the distal femur by a broad base, with no medullary involvement. Which genetic abnormality is the hallmark of this lesion?

. MYC amplification
. MDM2 and CDK4 amplification
. EWSR1-FLI1 translocation
. GNAS mutation
. RB1 deletion

Correct Answer & Explanation

. MDM2 and CDK4 amplification

Explanation

Parosteal osteosarcoma is a low-grade surface tumor classic for the posterior distal femur. It is driven by the amplification of MDM2 and CDK4 genes on chromosome 12q13-15.

Question 5970

Topic: 10. Pathology and Oncology

A 60-year-old male presents with a deep, painless thigh mass.

MRI reveals a predominantly fatty mass with thick nodular septations greater than 2 mm. What is the most appropriate initial step in management?

. Immediate transfemoral amputation
. Core needle biopsy
. Marginal excision without prior biopsy
. Preoperative radiation therapy
. Neoadjuvant systemic chemotherapy

Correct Answer & Explanation

. Core needle biopsy

Explanation

Thick septations (>2 mm) and nodularity in a deep fatty mass are highly suggestive of an atypical lipomatous tumor (ALT). A core needle biopsy is required to confirm the diagnosis and rule out a dedifferentiated component prior to definitive surgical planning.

Question 5971

Topic: 10. Pathology and Oncology

A 19-year-old male has a lytic, expansile metaphyseal lesion of the proximal tibia. MRI shows prominent fluid-fluid levels. Biopsy reveals blood-filled spaces lined by highly pleomorphic, atypical spindle cells producing osteoid matrix. What is the correct diagnosis?

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

Correct Answer & Explanation

. Telangiectatic osteosarcoma

Explanation

Telangiectatic osteosarcoma closely mimics an aneurysmal bone cyst (ABC) on imaging due to the presence of fluid-fluid levels. However, the presence of highly pleomorphic cells producing malignant osteoid confirms telangiectatic osteosarcoma.

Question 5972

Topic: Bone Tumors

A 10-year-old girl with hereditary multiple exostoses presents with progressive forearm deformity.

Which of the following describes the most classic pattern of forearm deformity seen in this condition?

. Ulnar shortening and radial bowing
. Radial shortening and ulnar bowing
. Proximal radioulnar synostosis
. Volar subluxation of the carpus
. Madelung deformity with positive ulnar variance

Correct Answer & Explanation

. Ulnar shortening and radial bowing

Explanation

The classic forearm deformity in HME features ulnar shortening relative to the radius, resulting in radial bowing and potential dislocation of the radial head. This occurs because osteochondromas disproportionately affect the growth of the distal ulna.

Question 5973

Topic: Bone Tumors

A 72-year-old man with a history of an enlarging skull and bowing of his long bones presents with severe, progressive right hip pain. Radiographs show mixed lytic and sclerotic changes in the hemipelvis with cortical destruction and an expansile soft tissue mass. What is the most likely underlying condition predisposing him to this malignancy?

. Fibrous dysplasia
. Paget's disease of bone
. Enchondromatosis
. Osteogenesis imperfecta
. Osteopetrosis

Correct Answer & Explanation

. Paget's disease of bone

Explanation

Secondary osteosarcoma typically occurs in older adults, most commonly arising in the setting of Paget's disease of bone or prior radiation therapy. Pagetoid osteosarcoma carries a significantly worse prognosis compared to primary conventional osteosarcoma.

Question 5974

Topic: 10. Pathology and Oncology

A 45-year-old female undergoes marginal excision of an intramuscular lipoma in her deltoid. Pathology confirms a benign lipoma with skeletal muscle fibers interspersed among mature adipocytes. What is the most important clinical consideration regarding this specific tumor type?

. It requires wide resection to prevent metastasis
. It has a high rate of malignant transformation to liposarcoma
. It is classically associated with PTEN mutations
. It has a higher local recurrence rate than subcutaneous lipomas if incompletely excised
. Adjuvant radiation is indicated to prevent recurrence

Correct Answer & Explanation

. It has a higher local recurrence rate than subcutaneous lipomas if incompletely excised

Explanation

Intramuscular lipomas are benign but have an infiltrative growth pattern, with skeletal muscle fibers commonly seen running through the fat on histology. Due to this infiltrative nature, they have a higher local recurrence rate than standard subcutaneous lipomas if not entirely excised.

Question 5975

Topic: Bone Tumors

A 16-year-old boy presents with an enlarging mass on the anterior aspect of his mid-tibia. Radiographs demonstrate a broad-based, surface lesion with a sunburst appearance and no medullary involvement. Histology reveals a predominantly chondroblastic matrix with intermediate-grade atypia. What is the diagnosis?

. Parosteal osteosarcoma
. Periosteal osteosarcoma
. Osteochondroma
. Chondrosarcoma
. Ewing sarcoma

Correct Answer & Explanation

. Periosteal osteosarcoma

Explanation

Periosteal osteosarcoma is an intermediate-grade surface tumor that typically arises on the diaphysis of long bones, most often the anterior tibia. It is predominantly chondroblastic histologically, distinguishing it from the fibroblastic, low-grade parosteal osteosarcoma.

Question 5976

Topic: 10. Pathology and Oncology

A 32-year-old male with Hereditary Multiple Exostoses presents for routine surveillance. He asks about his risk for developing a malignancy from his bone lesions. In which of the following anatomic locations is malignant transformation to chondrosarcoma most likely to occur?

. Distal femur
. Proximal tibia
. Pelvis
. Distal radius
. Calcaneus

Correct Answer & Explanation

. Pelvis

Explanation

In patients with HME, osteochondromas located in the axial skeleton, particularly the pelvis and proximal femur, carry the highest risk for malignant transformation. This transformation typically results in a secondary chondrosarcoma.

Question 5977

Topic: Bone Tumors

The standard neoadjuvant chemotherapy regimen for conventional high-grade osteosarcoma typically includes methotrexate, doxorubicin, and cisplatin. What is the primary antineoplastic mechanism of action of cisplatin?

. Dihydrofolate reductase inhibition
. Topoisomerase II inhibition
. Microtubule stabilization
. DNA cross-linking
. Vascular endothelial growth factor (VEGF) inhibition

Correct Answer & Explanation

. DNA cross-linking

Explanation

Cisplatin is an alkylating-like platinum compound that forms intra- and inter-strand DNA cross-links, preventing DNA replication and leading to apoptosis. Methotrexate inhibits dihydrofolate reductase, while doxorubicin inhibits topoisomerase II.

Question 5978

Topic: 10. Pathology and Oncology

A 65-year-old man undergoes resection of a massive retroperitoneal mass. Histology shows areas of mature fat with thick septations alongside discrete areas of high-grade, non-lipogenic pleomorphic spindle cells. Which of the following statements is true regarding this diagnosis?

. The low-grade and high-grade components have distinct, completely unrelated genetic mutations
. It arises from the malignant transformation of a standard subcutaneous lipoma
. It carries a higher risk of systemic metastasis compared to a well-differentiated liposarcoma
. MDM2 amplification is absent in the high-grade spindle cell component
. Surgery must always be followed by systemic high-dose methotrexate

Correct Answer & Explanation

. It carries a higher risk of systemic metastasis compared to a well-differentiated liposarcoma

Explanation

Dedifferentiated liposarcoma consists of a well-differentiated liposarcoma adjacent to a high-grade, non-lipogenic sarcoma. Both components share MDM2 amplification, but the dedifferentiated component significantly increases the risk for systemic metastasis.

Question 5979

Topic: 10. Pathology and Oncology

An 18-year-old male with a solitary osteochondroma of the distal femur presents with new-onset pain. An MRI is obtained to evaluate the cartilage cap. At what minimum cartilage cap thickness in an adult should the surgeon be highly concerned for malignant transformation?

. 0.5 cm
. 1.0 cm
. 2.0 cm
. 5.0 cm
. 10.0 cm

Correct Answer & Explanation

. 2.0 cm

Explanation

A cartilage cap thickness greater than 2.0 cm in a skeletally mature adult is highly suspicious for malignant transformation to a secondary chondrosarcoma. In actively growing children, the cap can normally be thicker (up to 3 cm).

Question 5980

Topic: 10. Pathology and Oncology

A 15-year-old boy is diagnosed with conventional osteosarcoma of the proximal tibia.

Before definitive surgical resection, which imaging modality is essential to properly identify skip metastases?

. Whole-body PET/CT
. Technetium-99m bone scan
. MRI of the entire affected bone
. CT of the chest with IV contrast
. High-resolution ultrasound

Correct Answer & Explanation

. MRI of the entire affected bone

Explanation

Skip metastases are distinct tumor foci within the same bone or transarticular bone that are separated from the primary tumor by normal marrow. An MRI of the entire affected bone (from joint to joint) is the gold standard to identify these lesions prior to definitive surgery.

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