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10. Pathology and Oncology MCQs

Practice Set 59 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 1161

Topic: 10. Pathology and Oncology

A 65-year-old male sustains a closed, completely displaced subtrochanteric femur fracture. Radiographs reveal a permeative lytic lesion with ring-and-arc calcifications in the area of the fracture. A core biopsy confirms Grade II conventional central chondrosarcoma. What is the most appropriate surgical management?

. Intramedullary nailing followed by radiation therapy
. Open reduction and internal fixation with locked plating
. Intralesional curettage, cementation, and prophylactic fixation
. Wide en bloc resection and endoprosthetic reconstruction
. Neoadjuvant chemotherapy followed by intramedullary nailing

Correct Answer & Explanation

. Wide en bloc resection and endoprosthetic reconstruction

Explanation

Pathologic fractures through a chondrosarcoma should be treated with wide en bloc resection and endoprosthetic reconstruction. Intramedullary nailing is contraindicated as it contaminates the entire medullary canal with tumor cells.

Question 1162

Topic: Bone Tumors

Somatic point mutations in which of the following genes are most heavily implicated in the pathogenesis of both solitary enchondromas and conventional central chondrosarcomas?

. EXT1 and EXT2
. IDH1 and IDH2
. p53 and RB1
. GNAS
. SOX9

Correct Answer & Explanation

. IDH1 and IDH2

Explanation

Mutations in IDH1 and IDH2 are found in over 50% of central conventional chondrosarcomas and enchondromas. EXT1/EXT2 mutations are associated with osteochondromas and secondary peripheral chondrosarcomas.

Question 1163

Topic: 10. Pathology and Oncology

According to the Mirels criteria for predicting the risk of a pathologic fracture, which of the following clinical profiles yields the highest score and strongly indicates the need for prophylactic internal fixation?

. Blastic lesion, upper extremity, size < 1/3 of cortex, mild pain
. Mixed lesion, upper extremity, size 1/3 to 2/3 of cortex, moderate pain
. Lytic lesion, lower extremity, size > 2/3 of cortex, severe pain
. Blastic lesion, lower extremity, size > 2/3 of cortex, mild pain
. Lytic lesion, upper extremity, size < 1/3 of cortex, moderate pain

Correct Answer & Explanation

. Lytic lesion, lower extremity, size > 2/3 of cortex, severe pain

Explanation

Mirels criteria score based on site, pain, lesion type (lytic > blastic), and size (> 2/3 cortex max score). A lytic lesion in the lower extremity taking up > 2/3 of the cortex with severe pain yields the maximum score of 12, heavily indicating prophylactic fixation.

Question 1164

Topic: 10. Pathology and Oncology

A 24-year-old female presents with a soft tissue mass in the thigh. Histologic evaluation shows a distinct biphasic pattern consisting of highly cellular areas of undifferentiated small round blue cells alternating with islands of well-differentiated hyaline cartilage. What is the most likely diagnosis?

. Dedifferentiated chondrosarcoma
. Clear cell chondrosarcoma
. Mesenchymal chondrosarcoma
. Synovial sarcoma
. Ewing sarcoma

Correct Answer & Explanation

. Mesenchymal chondrosarcoma

Explanation

Mesenchymal chondrosarcoma is characterized by a biphasic histologic pattern of small round blue cells and islands of hyaline cartilage. It is an aggressive variant that often occurs in young adults and may have an extraskeletal presentation.

Question 1165

Topic: 10. Pathology and Oncology

A 32-year-old male is evaluated for multiple bone lesions. He is diagnosed with Maffucci syndrome. Which clinical feature strictly differentiates Maffucci syndrome from Ollier disease?

. The presence of multiple osteochondromas
. The presence of cafe-au-lait spots
. The presence of soft tissue venous malformations
. Unilateral distribution of bone lesions
. Associated precocious puberty

Correct Answer & Explanation

. The presence of soft tissue venous malformations

Explanation

Maffucci syndrome is distinguished from Ollier disease by the presence of multiple soft tissue hemangiomas (venous malformations). Both syndromes feature multiple enchondromatosis, but Maffucci carries a higher risk of malignant transformation.

Question 1166

Topic: Bone Tumors

A 70-year-old woman is diagnosed with dedifferentiated chondrosarcoma of the proximal femur. Unlike conventional chondrosarcoma, the standard of care for this specific variant often involves which of the following adjuncts to wide surgical resection?

. Radiofrequency ablation
. High-dose proton beam radiation
. Osteoclast inhibitors only
. Systemic chemotherapy
. Intralesional phenol application

Correct Answer & Explanation

. Systemic chemotherapy

Explanation

Dedifferentiated chondrosarcoma features a high-grade, non-cartilaginous sarcomatous component (e.g., osteosarcoma or malignant fibrous histiocytoma). Treatment typically incorporates systemic chemotherapy directed at the high-grade component, unlike conventional chondrosarcoma which is chemoresistant.

Question 1167

Topic: 10. Pathology and Oncology
A 55-year-old male is scheduled for an internal hemipelvectomy for a massive Grade II chondrosarcoma of the pelvis. The preoperative plan involves the Enneking Type II resection. Which anatomical structure is primarily removed in this specific type of resection?
. The ilium alone
. The periacetabular region
. The pubis and ischium
. The entire hemipelvis and lower extremity
. The sacrum only

Correct Answer & Explanation

. The pubis and ischium

Explanation

In the Enneking classification of internal hemipelvectomies, Type I is an iliac resection, Type II is a periacetabular resection, and Type III is an obturator (pubis and ischium) resection.

Question 1168

Topic: 10. Pathology and Oncology

When evaluating a cartilaginous lesion in a long bone on MRI, which of the following features is the most reliable indicator of a low-grade conventional chondrosarcoma rather than a benign enchondroma?

. Intralesional lobular architecture
. High signal intensity on T2-weighted images
. Endosteal scalloping greater than two-thirds of the cortical thickness
. Presence of ring-and-arc calcifications
. Location in the hands or feet

Correct Answer & Explanation

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

Explanation

Deep endosteal scalloping (greater than two-thirds of the cortical thickness) and cortical penetration are highly suggestive of malignant behavior (chondrosarcoma) compared to an enchondroma.

Question 1169

Topic: Bone Tumors

Conventional central chondrosarcomas are generally considered radioresistant. In which of the following clinical scenarios is radiation therapy most clearly indicated for chondrosarcoma?

. A primary Grade I chondrosarcoma of the proximal femur
. An unresectable chondrosarcoma of the skull base
. A clear cell chondrosarcoma of the proximal humerus with wide margins
. A secondary chondrosarcoma arising from an osteochondroma
. To downsize a large pelvic tumor prior to hemipelvectomy

Correct Answer & Explanation

. An unresectable chondrosarcoma of the skull base

Explanation

While conventional chondrosarcoma is notoriously resistant to radiotherapy, high-dose radiation (often proton beam) is indicated for unresectable tumors or those with positive margins in critical locations, such as the base of the skull.

Question 1170

Topic: Bone Tumors

A 35-year-old male presents with a painless mass on the posterior surface of the distal femur. MRI reveals a surface lesion with lobulated cartilaginous matrix, ring-and-arc calcifications, and saucerization of the underlying cortex without medullary involvement. What is the most likely diagnosis?

. Parosteal osteosarcoma
. Periosteal osteosarcoma
. Periosteal chondroma
. Periosteal chondrosarcoma
. Osteochondroma

Correct Answer & Explanation

. Periosteal chondrosarcoma

Explanation

Periosteal chondrosarcoma presents as a surface lesion on a long bone with a distinct cartilaginous matrix and underlying cortical saucerization. It lacks medullary involvement, which distinguishes it from conventional central chondrosarcoma.

Question 1171

Topic: 10. Pathology and Oncology
Which of the following histologic findings is the definitive hallmark required to diagnose a dedifferentiated chondrosarcoma?
. A biphasic pattern of small round blue cells and well-differentiated cartilage
. An abrupt transition from a low-grade cartilaginous tumor to a high-grade, non-cartilaginous sarcoma
. The presence of osteoid production within malignant cartilage
. A continuous gradual transition from benign cartilage to Grade III chondrosarcoma
. The presence of cells with abundant clear cytoplasm and distinct borders

Correct Answer & Explanation

. An abrupt transition from a low-grade cartilaginous tumor to a high-grade, non-cartilaginous sarcoma

Explanation

The histologic hallmark of dedifferentiated chondrosarcoma is a sharp, abrupt transition between a low-grade cartilaginous component (often enchondroma or Grade 1 chondrosarcoma) and a high-grade, non-cartilaginous sarcomatous component.

Question 1172

Topic: 10. Pathology and Oncology

A 40-year-old male presents with a radiolucent epiphyseal lesion in the proximal humerus. Histology shows sheets of cells with abundant clear cytoplasm, distinct borders, and interspersed trabeculae of woven bone. What is the most likely diagnosis?

. Chondroblastoma
. Clear cell chondrosarcoma
. Giant cell tumor
. Osteosarcoma
. Enchondroma

Correct Answer & Explanation

. Clear cell chondrosarcoma

Explanation

Clear cell chondrosarcoma is a low-grade malignant tumor that classically arises in the epiphysis of older adults. It is differentiated from chondroblastoma, which typically occurs in skeletally immature patients.

Question 1173

Topic: 10. Pathology and Oncology

A 60-year-old female presents with a displaced pathologic subtrochanteric femur fracture. Biopsy of the underlying lytic lesion reveals a low-grade cartilaginous matrix abruptly transitioning into a high-grade spindle cell sarcoma. Which of the following is the most appropriate definitive management?

. Intramedullary nailing followed by radiation
. Wide resection and endoprosthetic reconstruction
. Curettage, cementation, and cephalomedullary nailing
. Amputation through the hip joint
. Neoadjuvant chemotherapy followed by open reduction internal fixation

Correct Answer & Explanation

. Wide resection and endoprosthetic reconstruction

Explanation

The diagnosis is dedifferentiated chondrosarcoma with a pathologic fracture. Intramedullary nailing is contraindicated as it spreads tumor cells; wide resection with endoprosthetic reconstruction is required.

Question 1174

Topic: Bone Tumors

Which of the following genetic mutations is most commonly associated with the pathogenesis of conventional central chondrosarcomas?

. EXT1
. IDH1/IDH2
. p53
. Rb
. GNAS

Correct Answer & Explanation

. IDH1/IDH2

Explanation

IDH1 and IDH2 mutations are found in a large majority of conventional central chondrosarcomas and enchondromas. EXT mutations are primarily associated with osteochondromas and peripheral chondrosarcomas.

Question 1175

Topic: 10. Pathology and Oncology
A 35-year-old male with Ollier disease complains of new, progressive thigh pain. Radiographs show a previously stable calcified lesion in the femoral diaphysis now exhibiting deep endosteal scalloping (>2/3 cortical thickness) and cortical breach. What is the most likely diagnosis?
. Mesenchymal chondrosarcoma
. Secondary conventional chondrosarcoma
. Dedifferentiated chondrosarcoma
. Enchondroma
. Clear cell chondrosarcoma

Correct Answer & Explanation

. Secondary conventional chondrosarcoma

Explanation

Ollier disease carries a high risk of malignant transformation of enchondromas into secondary conventional chondrosarcomas. Deep endosteal scalloping and cortical breakthrough are classic radiographic signs of this malignant transformation.

Question 1176

Topic: 10. Pathology and Oncology

A 25-year-old female presents with a destructive jaw mass. Histology demonstrates a biphasic pattern consisting of highly cellular areas of small round blue cells and abrupt islands of well-differentiated hyaline cartilage. A hemangiopericytoma-like vascular pattern is also noted. What is the diagnosis?

. Ewing sarcoma
. Dedifferentiated chondrosarcoma
. Mesenchymal chondrosarcoma
. Osteosarcoma
. Synovial sarcoma

Correct Answer & Explanation

. Mesenchymal chondrosarcoma

Explanation

Mesenchymal chondrosarcoma is a highly malignant tumor characterized by a biphasic histology of small round blue cells and islands of hyaline cartilage. It commonly affects the craniofacial bones and ribs in young adults.

Question 1177

Topic: Bone Tumors

A 45-year-old male is diagnosed with a grade 1 (low-grade) chondrosarcoma of the ilium. What is the recommended surgical management?

. Intralesional curettage with local adjuvant therapy
. Wide en bloc excision
. Radiation therapy alone
. Neoadjuvant chemotherapy followed by curettage
. Radiofrequency ablation

Correct Answer & Explanation

. Wide en bloc excision

Explanation

Unlike low-grade appendicular chondrosarcomas which can often be treated with extensive curettage, pelvic chondrosarcomas require wide en bloc excision. This is due to the high risk of local recurrence and subsequent dedifferentiation in the pelvis.

Question 1178

Topic: 10. Pathology and Oncology

In a patient with Multiple Hereditary Exostoses (MHE), which of the following imaging findings most strongly suggests malignant transformation of an osteochondroma into a secondary peripheral chondrosarcoma?

. Cartilage cap thickness of 5 mm
. Calcification within the cartilage cap
. A cartilage cap thickness greater than 2 cm in an adult
. Continuous medullary cavity with the host bone
. Location in the distal femur

Correct Answer & Explanation

. A cartilage cap thickness greater than 2 cm in an adult

Explanation

In adults, a cartilage cap thicker than 2 cm on MRI is highly suspicious for malignant transformation to a peripheral chondrosarcoma. MHE patients have an autosomal dominant EXT1/EXT2 mutation, putting them at increased risk.

Question 1179

Topic: 10. Pathology and Oncology

A 58-year-old patient undergoes resection of a large soft tissue mass. Pathology reveals a conventional grade II chondrosarcoma. Which of the following is the most important prognostic factor for this patient?

. Surgical margins
. Histologic grade
. Tumor size
. Presence of IDH1 mutation
. Patient age

Correct Answer & Explanation

. Histologic grade

Explanation

Histologic grade is the single most important prognostic factor for predicting metastasis and survival in conventional chondrosarcoma. Higher grade tumors have a significantly increased risk of systemic disease.

Question 1180

Topic: 10. Pathology and Oncology

A 65-year-old female with known metastatic breast cancer presents with a painful lytic lesion in her proximal femur. Using Mirels' criteria, which combination of findings yields the highest score, indicating prophylactic fixation?

. Upper extremity, blastic, <1/3 cortical diameter, mild pain
. Lower extremity, mixed, 1/3 to 2/3 cortical diameter, moderate pain
. Lower extremity, lytic, >2/3 cortical diameter, pain with weight-bearing
. Upper extremity, mixed, >2/3 cortical diameter, moderate pain
. Lower extremity, blastic, >2/3 cortical diameter, severe pain

Correct Answer & Explanation

. Lower extremity, lytic, >2/3 cortical diameter, pain with weight-bearing

Explanation

Mirels' criteria scores based on site, nature, size, and pain. A lower extremity (2), lytic (3), >2/3 diameter (3), and functional pain (3) yields a high score (11), heavily favoring prophylactic internal fixation.

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