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10. Pathology and Oncology MCQs

Practice Set 38 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 741

Topic: 10. Pathology and Oncology

A 65-year-old male with a long-standing, asymptomatic calcified lesion in the proximal femur suddenly develops severe, unremitting thigh pain. Radiographs reveal a large, unmineralized lytic destructive soft tissue mass extending from the pre-existing heavily calcified intramedullary lesion. What is the most likely diagnosis?

. Conventional high-grade osteosarcoma
. Secondary peripheral chondrosarcoma
. Clear cell chondrosarcoma
. Dedifferentiated chondrosarcoma
. Metastatic renal cell carcinoma

Correct Answer & Explanation

. Dedifferentiated chondrosarcoma

Explanation

Dedifferentiated chondrosarcoma typically presents as a high-grade, unmineralized sarcoma arising abruptly adjacent to a low-grade, heavily calcified enchondroma or chondrosarcoma. This biphasic radiographic and histologic appearance is highly characteristic.

Question 742

Topic: 10. Pathology and Oncology

A 14-year-old male with conventional high-grade osteosarcoma of the distal femur completes 10 weeks of neoadjuvant MAP (methotrexate, doxorubicin, cisplatin) chemotherapy followed by wide surgical resection. Pathologic evaluation of the resected specimen reveals 75% tumor necrosis. What is the most significant prognostic implication of this finding?

. Excellent prognosis indicating no further systemic chemotherapy is required
. Decreased overall survival compared to patients with >90% necrosis
. High risk of local recurrence regardless of surgical margins
. Strict indication to switch to adjuvant radiation therapy
. Need for immediate conversion to an above-knee amputation

Correct Answer & Explanation

. Decreased overall survival compared to patients with >90% necrosis

Explanation

The degree of tumor necrosis following neoadjuvant chemotherapy is the most important histologic prognostic factor in osteosarcoma. A poor response, defined as <90% necrosis, is associated with significantly decreased overall and disease-free survival.

Question 743

Topic: 10. Pathology and Oncology

A 42-year-old male presents with chronic shoulder pain. Radiographs show a well-circumscribed, lytic lesion in the epiphysis of the proximal humerus with subtle internal calcifications. Histology demonstrates cells with abundant clear cytoplasm and distinct cell membranes, mixed with benign giant cells. Which of the following is the most appropriate definitive treatment?

. Intralesional curettage and bone grafting
. Wide surgical resection
. Neoadjuvant chemotherapy followed by limb salvage
. Radiation therapy exclusively
. Radiofrequency ablation

Correct Answer & Explanation

. Wide surgical resection

Explanation

Clear cell chondrosarcoma is a low-grade malignant cartilage tumor that distinctively occurs in the epiphysis of long bones in adults, mimicking a chondroblastoma. Treatment requires wide surgical resection, as intralesional procedures lead to unacceptably high rates of local recurrence.

Question 744

Topic: 10. Pathology and Oncology

A 25-year-old male with multiple hereditary exostoses (MHE) reports rapid growth and new-onset pain in a sessile lesion on his proximal tibia. MRI reveals a cartilage cap thickness of 2.5 cm. What is the most appropriate surgical management?

. Core needle biopsy prior to any definitive intervention
. Wide en bloc resection
. Marginal excision preserving the pseudocapsule
. Intralesional curettage with phenol adjuvant
. Prophylactic internal fixation

Correct Answer & Explanation

. Wide en bloc resection

Explanation

A cartilage cap >2 cm in a skeletally mature patient with MHE is highly suspicious for malignant transformation to secondary chondrosarcoma. Wide en bloc resection is the treatment of choice to minimize recurrence risk.

Question 745

Topic: Bone Tumors

A 16-year-old girl presents with a destructive, expansile lytic lesion in the proximal humerus. MRI shows multiple fluid-fluid levels within the lesion, resembling an aneurysmal bone cyst (ABC), but with solid septal nodularity on contrast sequences. Which histologic feature most reliably differentiates this lesion from a primary ABC?

. The presence of hemosiderin-laden macrophages
. Expansion of the overlying cortical bone
. Identification of highly pleomorphic cells producing osteoid in the septa
. The presence of multinucleated giant cells
. Lack of active periosteal reaction

Correct Answer & Explanation

. Identification of highly pleomorphic cells producing osteoid in the septa

Explanation

Telangiectatic osteosarcoma frequently mimics an aneurysmal bone cyst radiographically and on MRI due to fluid-fluid levels. The definitive differentiating feature is the histologic presence of highly pleomorphic, malignant cells producing fine lace-like osteoid within the septal walls.

Question 746

Topic: 10. Pathology and Oncology

A 9-year-old boy is evaluated for multiple large, cortically based lucent lesions with sclerotic margins in his bilateral distal femurs and proximal tibias. Physical examination reveals multiple cafe-au-lait spots, but he lacks Lisch nodules and neurofibromas. Genetic testing for NF1 is negative. Which of the following is the most likely diagnosis?

. McCune-Albright syndrome
. Jaffe-Campanacci syndrome
. Mazabraud syndrome
. Ollier disease
. Maffucci syndrome

Correct Answer & Explanation

. Jaffe-Campanacci syndrome

Explanation

Jaffe-Campanacci syndrome is characterized by the presence of multiple non-ossifying fibromas (NOFs), cafe-au-lait macules, intellectual disability, and hypogonadism. It is clinically distinct from Neurofibromatosis type 1 (NF1).

Question 747

Topic: 10. Pathology and Oncology

A 24-year-old female presents with a destructive mass in the ilium. Histopathology demonstrates a biphasic pattern consisting of sheets of undifferentiated small round blue cells interspersed with well-defined islands of mature, benign-appearing hyaline cartilage. Which of the following molecular findings is most specific to this tumor?

. HEY1-NCOA2 fusion
. EWSR1-FLI1 fusion
. IDH1/IDH2 point mutations
. EXT1/EXT2 mutations
. MDM2 amplification

Correct Answer & Explanation

. HEY1-NCOA2 fusion

Explanation

Mesenchymal chondrosarcoma is an aggressive, high-grade tumor characterized histologically by a biphasic pattern of small round blue cells and islands of mature cartilage. The specific molecular driver for this tumor is the HEY1-NCOA2 gene fusion.

Question 748

Topic: 10. Pathology and Oncology

A 13-year-old boy is diagnosed with high-grade osteosarcoma of the proximal tibia. Imaging demonstrates tumor extension directly encasing the popliteal artery over a 4 cm segment and extensive invasion of the tibial nerve. What is the most appropriate definitive surgical management after neoadjuvant chemotherapy?

. Limb salvage with a modular endoprosthesis and vascular bypass
. Above-knee amputation
. Rotationplasty with primary nerve grafting
. Intralesional resection with liquid nitrogen cryotherapy
. Marginal resection followed by high-dose adjuvant radiotherapy

Correct Answer & Explanation

. Above-knee amputation

Explanation

Absolute contraindications to limb salvage in osteosarcoma include extensive major neurovascular bundle involvement that cannot be resected with negative margins. Above-knee amputation is required to ensure adequate oncologic clearance in this scenario.

Question 749

Topic: 10. Pathology and Oncology

A 14-year-old male presents with right distal femur pain and swelling for 3 months. Radiographs show a lytic lesion with a Codman's triangle and sunburst periosteal reaction. Biopsy confirms osteosarcoma. What is the most critical investigation for staging and treatment planning?

. Bone scan
. CT chest
. MRI of the entire affected limb
. PET scan
. Angiogram of the limb

Correct Answer & Explanation

. CT chest

Explanation

Correct Answer: BOsteosarcoma has a significant propensity for pulmonary metastasis, which is the most common site of distant spread. Therefore, a CT scan of the chest is the most critical investigation for staging, as the presence of lung metastases significantly impacts prognosis and dictates the extent of systemic treatment (e.g., neoadjuvant chemotherapy). While MRI of the affected limb is crucial for local staging and surgical planning, and a bone scan for other osseous metastases, identifying pulmonary metastases is paramount for systemic staging and overall treatment strategy.

Question 750

Topic: 10. Pathology and Oncology

When performing an incisional biopsy of a suspected soft-tissue sarcoma in the anterior thigh, which of the following principles must be strictly followed to avoid compromising future limb-salvage surgery?

. Use a transverse incision to follow Langer's lines for a better cosmetic scar
. Raise large medial and lateral fasciocutaneous flaps to expose the entire mass
. Place a longitudinal incision directly over the mass in line with the planned definitive resection
. Ensure the biopsy tract crosses at least two un-involved anatomic compartments to access the deep margins
. Avoid strict hemostasis as the hematoma will be resected later anyway

Correct Answer & Explanation

. Place a longitudinal incision directly over the mass in line with the planned definitive resection

Explanation

Biopsy tracts for suspected sarcomas must be excised during definitive surgery. Therefore, a longitudinal incision directly over the mass, avoiding transverse extensions and minimizing flap elevation or hematoma formation, is critical to prevent tumor seeding and allow future en bloc resection.

Question 751

Topic: 10. Pathology and Oncology
A 45-year-old patient has an incidental finding of a heavily calcified lesion in the proximal femur on an abdominal CT. Follow-up MRI and radiographs reveal endosteal scalloping involving >2/3 of the cortical thickness and soft tissue extension. The patient reports deep, aching thigh pain at night. What is the most likely diagnosis and appropriate treatment?
. Enchondroma; observe with serial radiographs
. Grade 2/3 Chondrosarcoma; wide surgical resection and reconstruction
. Osteoid osteoma; radiofrequency ablation
. Fibrous dysplasia; bisphosphonate therapy
. Ewing sarcoma; neoadjuvant chemotherapy followed by radiation

Correct Answer & Explanation

. Grade 2/3 Chondrosarcoma; wide surgical resection and reconstruction

Explanation

Endosteal scalloping greater than 2/3 cortical thickness, soft tissue extension, and nocturnal pain in the setting of a cartilaginous lesion are hallmarks of high-grade chondrosarcoma. Wide resection is the treatment of choice, as these tumors are notoriously resistant to chemotherapy and radiation.

Question 752

Topic: 10. Pathology and Oncology

A 15-year-old female presents with a blastic lesion and sunburst periosteal reaction in the distal femur. Biopsy confirms high-grade conventional osteosarcoma. Workup reveals no pulmonary metastases. What is the standard treatment protocol?

. Wide surgical resection alone
. Neoadjuvant chemotherapy, wide resection, and adjuvant chemotherapy
. Radiation therapy followed by resection
. Amputation followed by radiation therapy
. Intralesional curettage and bone grafting

Correct Answer & Explanation

. Neoadjuvant chemotherapy, wide resection, and adjuvant chemotherapy

Explanation

The standard of care for high-grade conventional osteosarcoma is neoadjuvant chemotherapy, wide surgical resection, and adjuvant chemotherapy. This protocol has significantly improved long-term survival.

Question 753

Topic: 10. Pathology and Oncology

A 60-year-old female presents with deep thigh pain. Radiographs show a lytic lesion with "popcorn" calcifications in the proximal femur metaphysis. Biopsy confirms a low-grade (Grade 1) chondrosarcoma. What is the most appropriate surgical treatment?

. Neoadjuvant chemotherapy followed by resection
. Wide surgical resection and endoprosthetic reconstruction
. Extensive intralesional curettage, adjuvant treatment, and cementation
. Neoadjuvant radiation followed by resection
. Observation with serial MRI

Correct Answer & Explanation

. Extensive intralesional curettage, adjuvant treatment, and cementation

Explanation

Low-grade (Grade 1) chondrosarcomas of the long bones can safely and effectively be managed with joint-sparing extensive intralesional curettage, local chemical/thermal adjuvants, and cementation.

Question 754

Topic: 10. Pathology and Oncology

A 15-year-old male presents with a mixed lytic and blastic lesion in the distal femoral metaphysis with periosteal reaction forming a Codman's triangle. Biopsy demonstrates malignant spindle cells producing osteoid matrix, confirming osteosarcoma. What is the most critical prognostic factor for this patient's long-term overall survival?

. Histologic grade of the initial biopsy
. Size of the primary tumor
. Patient age at diagnosis
. Percentage of tumor necrosis following neoadjuvant chemotherapy
. Presence of the t(11;22) chromosomal translocation

Correct Answer & Explanation

. Percentage of tumor necrosis following neoadjuvant chemotherapy

Explanation

The degree of tumor necrosis following neoadjuvant chemotherapy is the most important prognostic factor for overall survival in patients with high-grade, non-metastatic osteosarcoma. Greater than 90% necrosis is classified as a good histologic response and strongly correlates with improved outcomes.

Question 755

Topic: 10. Pathology and Oncology

A 15-year-old male complains of a rapidly growing, painful mass around his distal femur. Radiographs display a destructive metaphyseal lesion with a 'sunburst' periosteal reaction and elevation of the periosteum forming a Codman triangle. What is the most likely diagnosis?

. Ewing sarcoma
. Osteochondroma
. Chondrosarcoma
. Osteoid osteoma
. Osteosarcoma

Correct Answer & Explanation

. Osteosarcoma

Explanation

Osteosarcoma is the most common primary malignant bone tumor in children and adolescents, typically occurring in the metaphysis of long bones. The 'sunburst' pattern and Codman triangle are classic aggressive radiographic features of this tumor.

Question 756

Topic: 10. Pathology and Oncology

A 28-year-old male presents to the emergency department after a high-energy motor vehicle accident resulting in a knee dislocation. On initial assessment, the knee is grossly deformed. After successful closed reduction, palpable dorsalis pedis and posterior tibial pulses are present, but the ankle-brachial index (ABI) is measured at 0.85 on the affected limb. The patient denies paresthesias or severe pain, and the limb appears warm with good capillary refill. Which of the following is the MOST appropriate next step in management?

. Discharge with a hinged knee brace and close follow-up.
. Apply a posterior splint, admit for serial neurovascular checks every 4 hours for 24 hours.
. Order an immediate CT angiogram (CTA) of the affected limb.
. Proceed directly to surgical exploration of the popliteal artery.
. Obtain an MRI to assess ligamentous injuries before further vascular workup.

Correct Answer & Explanation

. Order an immediate CT angiogram (CTA) of the affected limb.

Explanation

Correct Answer: CThe case states that an ABI < 0.9 in an awake patient is highly suspicious for arterial injury and warrants further investigation, typically with a CT angiogram. While the limb appears viable and pulses are palpable, an ABI of 0.85 falls below this critical threshold, indicating a high probability of popliteal artery injury (e.g., intimal tear, partial occlusion) that may not yet manifest as overt ischemia. Delaying definitive diagnosis can lead to limb loss. Therefore, an immediate CT angiogram is the most appropriate next step to precisely delineate the vascular injury.Option A is incorrect as a knee dislocation is a severe injury with high complication rates and requires admission and comprehensive workup.Option B is insufficient. While serial neurovascular checks are important, an abnormal ABI mandates immediate advanced imaging (CTA) to rule out or characterize arterial injury, even in the absence of 'hard signs' or overt ischemia. The case explicitly states that if the ABI is normal (>0.9) and the physical examination is completely benign, serial clinical examinations may be an alternative, but not with an ABI of 0.85.Option D, proceeding directly to surgical exploration, is generally reserved for 'hard signs' of vascular injury (e.g., absent pulses, expanding hematoma, pulsatile bleeding, limb ischemia) where time is of the essence and imaging would cause undue delay. In this scenario, with palpable pulses and a viable limb, a CTA provides crucial information to guide the vascular surgeon and plan the repair, without significant delay.Option E is incorrect. While an MRI is essential for assessing ligamentous injuries, vascular assessment takes absolute priority in knee dislocations due to the limb-threatening nature of popliteal artery injury. MRI should be performed after vascular integrity is confirmed or addressed.

Question 757

Topic: 10. Pathology and Oncology

A 55-year-old male presents with a pathological fracture of the humerus through a large lytic lesion identified as metastatic carcinoma. The bone's significantly weakened resistance to bending and torsion at the lesion site is primarily a consequence of:

. Increased bone marrow edema within the lesion
. Reduced bone mineral density uniformly across the entire humerus
. A dramatic reduction in the Area Moment of Inertia at the lesion site
. Inflammatory cytokines released by tumor cells
. Disruption of the periosteal blood supply

Correct Answer & Explanation

. A dramatic reduction in the Area Moment of Inertia at the lesion site

Explanation

Correct Answer: CA large lytic lesion, by destroying bone tissue, significantly reduces the effective cross-sectional area of the bone and, more importantly, redistributes the remaining bone material closer to the neutral axis or eliminates it altogether. This results in a dramatic reduction in the Area Moment of Inertia (MOI) at the lesion site. The MOI is the geometric property that directly quantifies resistance to bending and torsional forces. This compromised MOI makes the bone extremely susceptible to pathological fracture under normal or even minimal physiological loads. While bone mineral density may be reduced and marrow edema present, the direct mechanical cause of fracture susceptibility is the compromised MOI due to the geometric defect.

Question 758

Topic: 10. Pathology and Oncology

A 25-year-old otherwise healthy male presents to the emergency department with acute onset of severe pain and inability to bear weight in his left thigh following a ground-level fall. He reports a 6-month history of a vague, dull ache in the same area. Initial radiographs of the left femur are shown below.

Based on the clinical presentation and radiographic findings, what is the most likely diagnosis?

. Osteosarcoma with pathological fracture
. Enchondroma with pathological fracture
. Fibrous Dysplasia with pathological fracture
. Aneurysmal Bone Cyst
. Metastatic Carcinoma

Correct Answer & Explanation

. Fibrous Dysplasia with pathological fracture

Explanation

Correct Answer: CThe clinical presentation of a young adult with a low-energy pathological fracture and a history of prodromal pain, combined with the classic radiographic appearance, strongly points to Fibrous Dysplasia. The initial radiographs (as shown) reveal a displaced, comminuted, transverse fracture of the mid-diaphyseal femur associated with a large, expansile, lytic lesion. Critically, the lesion exhibits the characteristic 'ground-glass' matrix appearance, significant cortical thinning, and endosteal scalloping. This 'ground-glass' appearance is pathognomonic for fibrous dysplasia, reflecting the immature woven bone and fibrous stroma within the lesion. While other lesions can cause pathological fractures, none typically present with this specific radiographic matrix. Osteosarcoma would typically show more aggressive features like periosteal reaction (e.g., sunburst, Codman's triangle), cortical destruction, and osteoid matrix. Enchondroma is usually a benign cartilaginous tumor, often asymptomatic, and would show chondroid matrix calcifications (rings and arcs) rather than ground-glass. Aneurysmal Bone Cyst (ABC) is purely lytic and expansile, often with fluid-fluid levels on MRI, but lacks a specific matrix on plain films. Metastatic carcinoma is less common in a 25-year-old without a known primary and would typically present as a purely lytic or blastic lesion without the ground-glass matrix.

Question 759

Topic: Bone Tumors

Following initial radiographs, an MRI of the left femur was performed to further characterize the lesion and rule out secondary aneurysmal bone cyst (ABC) or malignant transformation. The MRI findings included heterogeneous low-to-intermediate signal on T1-weighted images, high signal intensity on T2-weighted images, and heterogeneous, predominantly peripheral enhancement post-contrast. Crucially, no definitive fluid-fluid levels were identified. An example MRI image is provided.

Which of the following MRI findings, if present, would have most strongly suggested an alternative diagnosis of an Aneurysmal Bone Cyst (ABC) rather than Fibrous Dysplasia?

. Heterogeneous low-to-intermediate signal on T1-weighted images
. High signal intensity on T2-weighted images
. Prominent fluid-fluid levels
. Heterogeneous peripheral enhancement post-contrast
. Absence of aggressive soft tissue invasion

Correct Answer & Explanation

. Prominent fluid-fluid levels

Explanation

Correct Answer: CAneurysmal Bone Cysts (ABCs) are characterized by blood-filled spaces separated by fibrous septa. On MRI, the classic and most diagnostic feature of an ABC is the presence of prominent fluid-fluid levels, which represent the sedimentation of blood products within these cystic spaces. While fibrous dysplasia can sometimes have cystic degeneration or hemorrhage, leading to areas of high T2 signal and heterogeneous enhancement, it typically lacks definitive fluid-fluid levels unless a secondary ABC has developed within the fibrous dysplastic lesion. The other options (heterogeneous T1 signal, high T2 signal, and heterogeneous enhancement) are non-specific and can be seen in both fibrous dysplasia and ABCs, as well as other bone lesions. The absence of aggressive soft tissue invasion is a feature that helps rule out high-grade malignancy but does not differentiate between fibrous dysplasia and ABC.

Question 760

Topic: 10. Pathology and Oncology

A 25-year-old male presents with a displaced pathological fracture of the mid-diaphyseal femur through an expansile lytic lesion. The lesion involves more than two-thirds of the cortical diameter, and the patient reported moderate chronic pain prior to the acute fracture. Urgent operative intervention is planned. Applying the Mirels' scoring system to this patient's presentation, which of the following scores and corresponding management recommendations is most appropriate?

. Score of 7, indicating prophylactic fixation is optional.
. Score of 8, indicating prophylactic fixation is recommended.
. Score of 10, indicating urgent operative stabilization is required.
. Score of 6, indicating non-operative management may be considered.
. Score of 9, indicating biopsy before any fixation.

Correct Answer & Explanation

. Score of 10, indicating urgent operative stabilization is required.

Explanation

Correct Answer: CThe Mirels' scoring system is used to assess the risk of impending pathological fracture and guide management. The score is calculated based on four parameters:Location:Femur (3 points)Pain:Moderate (2 points, for chronic pain leading up to acute fracture)Lesion Size:>2/3 cortical diameter (3 points, as the lesion was expansive and involved most of the diaphyseal circumference)Nature of Lesion:Lytic (2 points)Therefore, the total Mirels' score for this patient is 3 + 2 + 3 + 2 = 10 points. A Mirels' score of 9 or greater indicates a very high risk of pathological fracture (or, as in this case, an already present fracture) and mandates urgent operative stabilization. Scores of 7-8 typically recommend prophylactic fixation, while scores of <7 may allow for non-operative management or observation, depending on the specific clinical context. Given the existing displaced fracture, urgent stabilization is unequivocally required.

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