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10. Pathology and Oncology MCQs

Practice Set 33 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 641

Topic: 10. Pathology and Oncology

Which of the following genetic mutations is most commonly associated with Hereditary Multiple Exostoses (HME), and what is the primary function of the proteins encoded by these genes?

. TP53; tumor suppressor involved in cell cycle regulation.
. EXT1 or EXT2; glycosyltransferases involved in heparan sulfate synthesis.
. COL1A1; collagen synthesis, important for bone matrix formation.
. IDH1 or IDH2; enzymes involved in cellular metabolism and epigenetics.
. FGFR3; receptor tyrosine kinase involved in chondrocyte proliferation and differentiation.

Correct Answer & Explanation

. EXT1 or EXT2; glycosyltransferases involved in heparan sulfate synthesis.

Explanation

Correct Answer: BAcademic Rationale:Hereditary Multiple Exostoses (HME), also known as Multiple Osteochondromas, is an autosomal dominant disorder caused by germline mutations in either theEXT1 or EXT2 genes. These genes encode glycosyltransferases that are crucial for the synthesis of heparan sulfate proteoglycans, which are vital components of the extracellular matrix and play a role in regulating growth factor signaling at the growth plate. Disruption of heparan sulfate synthesis is thought to lead to the aberrant growth plate function that characterizes osteochondroma formation.Option A (TP53):TP53 is a tumor suppressor gene associated with various cancers, including sarcomas (e.g., Li-Fraumeni syndrome), but not directly with HME.Option C (COL1A1):COL1A1 mutations are primarily associated with osteogenesis imperfecta, a disorder of collagen synthesis leading to brittle bones.Option D (IDH1 or IDH2):Mutations in IDH1 and IDH2 are found in some chondrosarcomas (including secondary chondrosarcomas) and other cancers, but they are not the primary cause of HME itself.Option E (FGFR3):FGFR3 mutations are associated with achondroplasia, a common form of dwarfism, affecting endochondral ossification.

Question 642

Topic: 10. Pathology and Oncology

A 4-year-old child is diagnosed with an asymptomatic osteochondroma of the proximal fibula. The parents are concerned about its long-term implications. What is the most important potential complication to monitor for in this specific location during childhood?

. Malignant transformation to chondrosarcoma.
. Fracture through the stalk of the osteochondroma.
. Compression of the common peroneal nerve leading to foot drop.
. Development of a pseudoaneurysm of the anterior tibial artery.
. Progressive genu varum deformity.

Correct Answer & Explanation

. Compression of the common peroneal nerve leading to foot drop.

Explanation

Correct Answer: CAcademic Rationale:An osteochondroma of the proximal fibula is particularly concerning due to its close proximity to thecommon peroneal nerveas it wraps around the fibular neck. Compression of this nerve can lead to a progressive foot drop (weakness in dorsiflexion and eversion of the foot), which is a significant functional impairment. Therefore, monitoring for neurological symptoms is paramount in this location.Option A (Malignant transformation):Malignant transformation is exceedingly rare in children, especially in a 4-year-old, and is a concern primarily in adults.Option B (Fracture through the stalk):While possible, fracture is typically an acute event following trauma and less of a long-term monitoring concern compared to nerve compression in this specific location.Option D (Pseudoaneurysm):Pseudoaneurysm is a vascular complication, more commonly associated with larger lesions in the popliteal fossa, not typically the proximal fibula.Option E (Progressive genu varum deformity):While angular deformities are common in HME, a proximal fibular osteochondroma is more likely to cause valgus deformity at the knee (due to tethering of the lateral side of the proximal tibia physis) or ankle deformity, rather than genu varum.

Question 643

Topic: 10. Pathology and Oncology

Which of the following is the most accurate statement regarding the histological appearance of a benign osteochondroma's cartilage cap?

. It consists of disorganized, hypercellular cartilage with numerous mitotic figures.
. It is composed of mature fibrocartilage with scattered calcifications.
. It resembles a normal growth plate, with well-organized hyaline cartilage and columnar chondrocytes undergoing endochondral ossification.
. It shows invasion into the underlying bony stalk and adjacent soft tissues.
. It is a thin layer of elastic cartilage with a prominent perichondrial layer.

Correct Answer & Explanation

. It resembles a normal growth plate, with well-organized hyaline cartilage and columnar chondrocytes undergoing endochondral ossification.

Explanation

Correct Answer: CAcademic Rationale:The defining histological feature of a benign osteochondroma's cartilage cap is that itresembles a normal growth plate. It is composed of well-organized hyaline cartilage, with chondrocytes arranged in columns at its base, undergoing endochondral ossification to form the underlying bone of the exostosis. This similarity to a physis explains its growth pattern during childhood.Option A (Disorganized, hypercellular cartilage with numerous mitotic figures):These features (hypercellularity, disorganization, increased mitoses) are characteristic of malignant transformation to chondrosarcoma, not a benign osteochondroma.Option B (Mature fibrocartilage with scattered calcifications):The cap is hyaline cartilage, not fibrocartilage. While calcifications can occur, the primary composition is hyaline.Option D (Invasion into underlying bony stalk and adjacent soft tissues):Invasion into soft tissues is a hallmark of malignancy. A benign osteochondroma has a well-defined interface.Option E (Thin layer of elastic cartilage):The cap is hyaline cartilage, not elastic cartilage, and its thickness can vary.

Question 644

Topic: Bone Tumors

A 15-year-old boy has a large, sessile osteochondroma of the distal ulna causing progressive ulnar deviation of the wrist and forearm rotation limitation (Madelung-like deformity). He is skeletally immature. What is the most appropriate surgical strategy to address this condition?

. Simple excision of the osteochondroma and observation for deformity correction.
. Excision of the osteochondroma combined with a corrective osteotomy and possibly guided growth of the radius/ulna.
. Proximal ulnar osteotomy to shorten the ulna without excising the osteochondroma.
. Radiation therapy to halt the growth of the osteochondroma and correct deformity.
. Arthrodesis of the distal radioulnar joint to stabilize the wrist.

Correct Answer & Explanation

. Excision of the osteochondroma combined with a corrective osteotomy and possibly guided growth of the radius/ulna.

Explanation

Correct Answer: BAcademic Rationale:When an osteochondroma, particularly in the distal ulna, causes significant angular deformity and functional limitation (like a Madelung-like deformity) in a skeletally immature patient, simple excision of the osteochondroma alone is often insufficient to correct the existing deformity. The most appropriate surgical strategy isexcision of the osteochondroma combined with a corrective osteotomy(e.g., of the ulna or radius) to realign the limb and, if significant growth potential remains, possibly guided growth (e.g., hemiepiphysiodesis) to modulate future growth and prevent recurrence of the deformity. This comprehensive approach addresses both the mass and the resulting skeletal malalignment.Option A (Simple excision and observation):Simple excision may relieve impingement but will not correct a pre-existing angular deformity. Observation would allow the deformity to persist or worsen.Option C (Proximal ulnar osteotomy without excision):This would address the length discrepancy but not the underlying osteochondroma or its potential for continued growth and recurrence of the deformity.Option D (Radiation therapy):Radiation therapy is not indicated for benign osteochondromas and carries risks of radiation-induced malignancy and growth disturbance.Option E (Arthrodesis of DRUJ):Arthrodesis is a salvage procedure that sacrifices motion and is not indicated as a primary treatment for a correctable deformity in a skeletally immature patient.

Question 645

Topic: 10. Pathology and Oncology

A 45-year-old male presents with a long-standing, asymptomatic osteochondroma of the proximal humerus. He reports no pain or functional limitations. Which of the following is the most appropriate management plan?

. Immediate surgical excision to prevent future complications.
. Annual MRI scans to monitor for malignant transformation.
. Observation with reassurance, as surgical intervention is rarely needed for asymptomatic lesions.
. Percutaneous biopsy to confirm benign nature.
. Radiation therapy to prevent growth.

Correct Answer & Explanation

. Observation with reassurance, as surgical intervention is rarely needed for asymptomatic lesions.

Explanation

Correct Answer: CAcademic Rationale:For an asymptomatic osteochondroma in an adult, particularly one that has been stable since skeletal maturity, the most appropriate management isobservation with reassurance. Osteochondromas typically cease growth at skeletal maturity, and the risk of malignant transformation for a solitary lesion is very low (less than 1%). Surgical intervention is reserved for symptomatic lesions (pain, functional limitation, neurovascular compression) or those with suspicious features of malignant transformation.Option A (Immediate surgical excision):Unnecessary for an asymptomatic, stable lesion, and exposes the patient to surgical risks without clear benefit.Option B (Annual MRI scans):While MRI is excellent for evaluating cartilage cap, annual scans are excessive and costly for an asymptomatic, stable lesion. Imaging is typically reserved for new symptoms or suspicious findings.Option D (Percutaneous biopsy):Biopsy is an invasive procedure and is not indicated for an asymptomatic lesion unless there are clinical or radiological signs suggestive of malignancy.Option E (Radiation therapy):Radiation therapy is not used for benign osteochondromas due to its ineffectiveness and potential for inducing secondary malignancies.

Question 646

Topic: 10. Pathology and Oncology

When differentiating a sessile osteochondroma from a parosteal osteosarcoma on plain radiographs and CT scans, which feature is most crucial for establishing the diagnosis of an osteochondroma?

. The presence of a 'sunburst' periosteal reaction.
. A purely lytic lesion with a sclerotic rim.
. Continuity of the cortex and medullary cavity of the lesion with the parent bone.
. The presence of a large soft tissue mass with internal calcifications.
. A clear cleavage plane between the lesion and the underlying cortex.

Correct Answer & Explanation

. Continuity of the cortex and medullary cavity of the lesion with the parent bone.

Explanation

Correct Answer: CAcademic Rationale:The most crucial and pathognomonic radiographic feature that distinguishes an osteochondroma from other surface lesions, including parosteal osteosarcoma, is thecontinuity of the cortex and medullary cavity of the exostosis with the parent bone. This 'continuity sign' confirms that the lesion is an outgrowth of the native bone. Parosteal osteosarcoma, while also a surface lesion, typically has a clear cleavage plane between the tumor and the underlying cortex, and its medullary cavity is not continuous with the parent bone.Option A (Sunburst periosteal reaction):A 'sunburst' periosteal reaction is highly suggestive of an aggressive malignant bone tumor, such as osteosarcoma, and is not seen in benign osteochondromas.Option B (Purely lytic lesion with sclerotic rim):This description is more characteristic of an osteoid osteoma or other benign lytic lesions, not an osteochondroma, which is an osteocartilaginous exostosis.Option D (Large soft tissue mass with internal calcifications):While a large cartilage cap can have calcifications, a prominent soft tissue mass with irregular calcifications is more concerning for a malignant cartilaginous tumor (chondrosarcoma) or other soft tissue sarcoma.Option E (Clear cleavage plane between lesion and underlying cortex):A clear cleavage plane is characteristic of parosteal osteosarcoma, indicating it is separate from the underlying cortex, which is the opposite of an osteochondroma.

Question 647

Topic: 10. Pathology and Oncology
A 15-year-old boy presents with progressive distal thigh pain. Imaging reveals a destructive metaphyseal lesion with a "sunburst" periosteal reaction and Codman's triangle. Following neoadjuvant chemotherapy, what percentage of tumor necrosis is considered the threshold for a favorable prognostic response?
. 50%
. 70%
. 90%
. 95%
. 99%

Correct Answer & Explanation

. 90%

Explanation

In osteosarcoma, the histologic response to neoadjuvant chemotherapy is a major prognostic factor. Tumor necrosis of 90% or greater (Huvos grade III or IV) is considered a good response and correlates with improved survival.

Question 648

Topic: 10. Pathology and Oncology

A 12-year-old boy presents with a diaphyseal femur lesion with an "onion-skin" periosteal reaction. Biopsy shows small round blue cells. Which chromosomal translocation is most characteristically associated with this diagnosis?

. t(11;22)
. t(X;18)
. t(9;22)
. t(12;16)
. t(2;13)

Correct Answer & Explanation

. t(11;22)

Explanation

Ewing sarcoma is characterized by the t(11;22) translocation in over 90% of cases, resulting in the EWS-FLI1 fusion protein. The t(X;18) translocation is seen in synovial sarcoma, and t(9;22) in myxoid chondrosarcoma.

Question 649

Topic: Soft Tissue Tumors & Metastasis

A 65-year-old man presents with a pathologic fracture of the proximal humerus. Workup reveals a solitary, highly destructive lytic lesion and a primary renal cell carcinoma. Prior to surgical fixation and curettage, what is the most appropriate next step?

. Neoadjuvant radiation therapy
. Preoperative selective arterial embolization
. Systemic chemotherapy
. Intralesional steroid injection
. Radiofrequency ablation

Correct Answer & Explanation

. Preoperative selective arterial embolization

Explanation

Renal cell carcinoma and thyroid carcinoma metastases are notoriously hypervascular. Preoperative selective arterial embolization is recommended 24-48 hours before surgery to dramatically reduce intraoperative blood loss.

Question 650

Topic: Bone Tumors

A 19-year-old male complains of severe right thigh pain that is worse at night and dramatically relieved by ibuprofen. CT demonstrates a 7mm radiolucent nidus surrounded by dense sclerotic bone in the femoral diaphysis. What is the most definitive and minimally invasive treatment?

. En bloc resection
. Observation
. Radiofrequency ablation
. Intralesional curettage
. Radiation therapy

Correct Answer & Explanation

. Radiation therapy

Explanation

Osteoid osteomas present classically with nocturnal pain relieved by NSAIDs due to high local prostaglandin levels. Radiofrequency ablation (RFA) is the treatment of choice, offering high success rates with minimal morbidity.

Question 651

Topic: 10. Pathology and Oncology

A 14-year-old boy presents with chronic knee pain. Radiographs reveal a well-circumscribed lytic lesion with a sclerotic margin localized entirely within the proximal tibial epiphysis. Histology shows polygonal chondroblasts and "chicken-wire" calcification. What is the most likely diagnosis?

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

Correct Answer & Explanation

. Chondroblastoma

Explanation

Chondroblastoma is a rare, benign cartilage tumor that characteristically occurs in the epiphysis or apophysis of long bones in skeletally immature patients. "Chicken-wire" calcification is a pathognomonic histologic finding.

Question 652

Topic: Bone Tumors

A 65-year-old woman presents with multiple "punched-out" lytic bone lesions. Serum protein electrophoresis reveals an M-spike. Which of the following is the most sensitive imaging modality for detecting skeletal involvement in this specific disease?

. Technetium-99m bone scan
. Whole-body low-dose CT or PET/CT
. Plain radiographs
. Ultrasound
. Dual-energy X-ray absorptiometry

Correct Answer & Explanation

. Whole-body low-dose CT or PET/CT

Explanation

Multiple myeloma lesions are primarily osteolytic without significant osteoblastic activity, making Technetium-99m bone scans notoriously falsely negative. Whole-body low-dose CT or PET/CT are the preferred sensitive modalities.

Question 653

Topic: 10. Pathology and Oncology

A 10-year-old girl is evaluated for a minor knee sprain. X-rays serendipitously reveal a 2 cm eccentric, multilobulated, lucent lesion with a sclerotic rim in the distal femoral metaphysis. It does not breach the cortex. What is the recommended management?

. Biopsy to rule out malignancy
. Intralesional curettage and bone grafting
. Observation and reassurance
. Prophylactic internal fixation
. Radiofrequency ablation

Correct Answer & Explanation

. Observation and reassurance

Explanation

The radiographic appearance is classic for a non-ossifying fibroma (NOF), a benign, asymptomatic developmental defect of bone. They typically regress and ossify as the child reaches skeletal maturity, requiring only observation.

Question 654

Topic: 10. Pathology and Oncology

A 25-year-old female presents with a painless, slow-growing mass at the posterior aspect of her distal femur. Radiographs show a densely ossified, broad-based mass on the cortical surface with a radiolucent cleft between the tumor and the underlying cortex. What genetic abnormality is most characteristic of this lesion?

. t(11;22) translocation
. MDM2 gene amplification
. GNAS mutation
. EXT1 gene mutation
. p53 mutation

Correct Answer & Explanation

. MDM2 gene amplification

Explanation

Parosteal osteosarcoma is a low-grade surface osteosarcoma characterized by a dense mass with a 'string sign' (radiolucent cleft). It is strongly associated with MDM2 and CDK4 gene amplifications on chromosome 12q13-15.

Question 655

Topic: 10. Pathology and Oncology

A 12-year-old boy presents with thigh pain, fever, and a diaphyseal lytic lesion in his femur with 'onion-skin' periosteal reaction. Histology shows small round blue cells. Which immunohistochemical marker is highly specific for this diagnosis?

. CD99
. S-100
. Cytokeratin
. Desmin
. Vimentin

Correct Answer & Explanation

. CD99

Explanation

This clinical picture is classic for Ewing sarcoma, which is characterized by small round blue cells and t(11;22) translocation. CD99 (MIC2) is a highly sensitive surface marker diffusely expressed in Ewing sarcoma.

Question 656

Topic: 10. Pathology and Oncology

A 14-year-old male presents with chronic knee pain. Radiographs show a well-circumscribed 2 cm lytic lesion with a thin sclerotic margin located entirely within the proximal tibial epiphysis. There is a small amount of fine calcification within the matrix. What is the most likely diagnosis?

. Chondromyxoid fibroma
. Osteochondroma
. Chondroblastoma
. Unicameral bone cyst
. Aneurysmal bone cyst

Correct Answer & Explanation

. Chondroblastoma

Explanation

Chondroblastoma is a rare, benign cartilage tumor that characteristically occurs in the epiphysis or apophysis of long bones in skeletally immature patients. Histology typically shows chondroblasts with 'chicken-wire' calcifications.

Question 657

Topic: Bone Tumors

A 19-year-old male complains of right thigh pain that is worse at night and completely relieved by ibuprofen. Imaging reveals a 1 cm radiolucent nidus surrounded by dense reactive sclerosis in the femoral diaphysis. If left untreated, what is the natural history of this lesion?

. Malignant transformation to osteosarcoma
. Progressive enlargement leading to a pathologic fracture
. Spontaneous resolution over several years
. Transformation into an aneurysmal bone cyst
. Metastasis to the lungs

Correct Answer & Explanation

. Spontaneous resolution over several years

Explanation

The presentation is classic for an osteoid osteoma. If left untreated, the natural history of osteoid osteoma is spontaneous resolution (burnout) over a period of 2 to 6 years, though treatment is often pursued for symptom relief.

Question 658

Topic: 10. Pathology and Oncology

What is the most important prognostic factor for long-term survival in a 14-year-old male with non-metastatic conventional osteosarcoma of the distal femur treated with neoadjuvant chemotherapy and surgical resection?

. Tumor volume at initial presentation
. Percent of tumor necrosis at the time of definitive resection
. Type of surgical reconstruction performed
. Alkaline phosphatase level at initial presentation
. Presence of a skip metastasis on pre-operative MRI

Correct Answer & Explanation

. Percent of tumor necrosis at the time of definitive resection

Explanation

The percentage of tumor necrosis following neoadjuvant chemotherapy (specifically >90% necrosis) is the single most important prognostic indicator for overall survival in conventional osteosarcoma.

Question 659

Topic: 10. Pathology and Oncology

A 12-year-old boy presents with a permeative diaphyseal lesion in the fibula with an associated "onion-skin" periosteal reaction. Biopsy reveals small blue round cells. Which of the following chromosomal translocations is most characteristic of this diagnosis?

. t(X;18)
. t(11;22)
. t(2;13)
. t(12;16)
. t(9;22)

Correct Answer & Explanation

. t(11;22)

Explanation

Ewing sarcoma is classically associated with the t(11;22) translocation, resulting in the EWS-FLI1 fusion protein. The t(X;18) translocation is seen in synovial sarcoma.

Question 660

Topic: 10. Pathology and Oncology

A 65-year-old man presents with a pathologic fracture of the proximal humerus secondary to a biopsy-proven renal cell carcinoma metastasis. What is the most appropriate next step prior to surgical stabilization?

. Neoadjuvant radiation therapy
. Administration of high-dose methotrexate
. Preoperative arterial embolization of the lesion
. Immediate intramedullary nailing without further intervention
. Wide en bloc resection with endoprosthetic reconstruction

Correct Answer & Explanation

. Preoperative arterial embolization of the lesion

Explanation

Renal cell carcinoma (and thyroid carcinoma) bone metastases are highly vascular. Preoperative arterial embolization is recommended 24 to 48 hours prior to surgery to minimize massive intraoperative blood loss.

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