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10. Pathology and Oncology MCQs

Practice Set 58 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 1141

Topic: Bone Tumors

Conventional chondrosarcomas are notoriously resistant to standard chemotherapy. Which of the following best explains this resistance?

. High rate of cellular proliferation and turnover
. Expression of the MDR-1 gene and poor vascularity of the chondroid matrix
. Absence of the TP53 mutation in all grades
. Overexpression of HER2 receptors
. High sensitivity to hypoxia-inducible factors

Correct Answer & Explanation

. Expression of the MDR-1 gene and poor vascularity of the chondroid matrix

Explanation

Conventional chondrosarcomas are largely resistant to chemotherapy due to their slow-growing nature, the poor vascularity of the hyaline cartilage matrix preventing drug penetration, and the expression of multidrug resistance (MDR-1) P-glycoprotein.

Question 1142

Topic: 10. Pathology and Oncology

A 68-year-old male with Grade II chondrosarcoma of the proximal femur develops a pathologic subtrochanteric fracture. What is the most appropriate surgical approach?

. Cephalomedullary nailing
. Wide resection of the proximal femur and proximal femoral replacement
. Intralesional curettage, cementation, and dynamic hip screw
. Open reduction and internal fixation with a locking plate
. Spica casting until fracture heals, followed by resection

Correct Answer & Explanation

. Wide resection of the proximal femur and proximal femoral replacement

Explanation

A pathologic fracture through a high-grade primary bone sarcoma contaminates the local tissue compartments with tumor cells. The treatment requires wide en bloc resection of the fracture hematoma and tumor, typically followed by endoprosthetic reconstruction.

Question 1143

Topic: 10. Pathology and Oncology

When performing a core needle biopsy of a suspected chondrosarcoma in the distal femur, which of the following principles is most critical to adhere to?

. The biopsy tract should be placed transversely across the extremity
. The biopsy tract must be longitudinally oriented and excisable during definitive resection
. A tourniquet should be inflated and deflated multiple times during the procedure
. The biopsy should routinely traverse multiple muscle compartments to ensure adequate sampling
. Intramedullary reaming should follow the biopsy to obtain marrow samples

Correct Answer & Explanation

. The biopsy tract must be longitudinally oriented and excisable during definitive resection

Explanation

Biopsy tracts are considered contaminated with tumor cells. It is a fundamental oncologic principle that the biopsy tract must be longitudinally oriented and placed in-line with the planned surgical incision so it can be excised en bloc with the tumor.

Question 1144

Topic: 10. Pathology and Oncology

Which genetic mutation is most commonly associated with the development of multiple hereditary exostoses (MHE) and carries a risk for malignant transformation into secondary peripheral chondrosarcoma?

. EXT1 and EXT2
. IDH1 and IDH2
. GNAS
. p53 and RB1
. c-myc

Correct Answer & Explanation

. EXT1 and EXT2

Explanation

Multiple hereditary exostoses (MHE) is an autosomal dominant condition caused by mutations in the EXT1 or EXT2 tumor suppressor genes. Patients have a 1-5% lifetime risk of malignant transformation into secondary peripheral chondrosarcoma.

Question 1145

Topic: 10. Pathology and Oncology
A 55-year-old male undergoes wide resection of a Grade III conventional chondrosarcoma of the distal femur. Three years later, he presents with a new solitary pulmonary nodule. Which of the following is true regarding metastasis in this disease?
. Lymphatic spread is the most common route of metastasis
. Grade I tumors have a higher rate of metastasis than Grade III tumors
. The lungs are the most common site of distant metastasis due to hematogenous spread
. Metastatic chondrosarcoma is highly responsive to methotrexate
. Prophylactic whole lung irradiation is standard of care after primary resection

Correct Answer & Explanation

. The lungs are the most common site of distant metastasis due to hematogenous spread

Explanation

Like most primary bone sarcomas, chondrosarcoma spreads primarily via the hematogenous route, making the lungs the most frequent site for distant metastasis. Grade III tumors have a significantly higher metastatic potential than Grade I.

Question 1146

Topic: Bone Tumors

Differentiating a large enchondroma from a low-grade (Grade I) central chondrosarcoma can be challenging. Which MRI finding is most highly specific for a diagnosis of chondrosarcoma over an enchondroma?

. High signal intensity on T2-weighted images
. Presence of lobulated cartilage architecture
. Deep endosteal scalloping greater than two-thirds of cortical thickness
. Punctate calcifications on corresponding radiographs
. Location in the small bones of the hands or feet

Correct Answer & Explanation

. Deep endosteal scalloping greater than two-thirds of cortical thickness

Explanation

While both lesions exhibit high T2 signal and punctate calcifications, deep endosteal scalloping (>2/3 of cortical thickness), cortical thickening, and soft tissue extension are aggressive features that strongly favor a diagnosis of chondrosarcoma.

Question 1147

Topic: 10. Pathology and Oncology

A 45-year-old male presents with chronic hip pain. Radiographs demonstrate a lytic lesion in the proximal femoral epiphysis with minor calcification. Biopsy reveals large cells with distinct borders, abundant clear cytoplasm, and centrally located nuclei amidst a cartilaginous matrix. Which of the following is the most likely diagnosis?

. Chondroblastoma
. Clear cell chondrosarcoma
. Giant cell tumor of bone
. Osteosarcoma
. Conventional central chondrosarcoma

Correct Answer & Explanation

. Clear cell chondrosarcoma

Explanation

Clear cell chondrosarcoma typically presents in the epiphysis of long bones in adults (30-50 years old), unlike chondroblastoma which affects the epiphysis of skeletally immature patients. It is a low-grade malignancy requiring wide surgical resection.

Question 1148

Topic: 10. Pathology and Oncology

Which of the following genetic mutations is most strongly associated with multiple hereditary exostoses (MHE) and carries a heightened risk for secondary chondrosarcoma?

. p53
. RB1
. GNAS
. EXT1 and EXT2
. NF1

Correct Answer & Explanation

. EXT1 and EXT2

Explanation

Multiple hereditary exostoses (osteochondromatosis) is an autosomal dominant condition caused by mutations in the EXT1 or EXT2 tumor suppressor genes. Patients have a 1% to 5% lifetime risk of malignant transformation to a secondary chondrosarcoma.

Question 1149

Topic: 10. Pathology and Oncology

A 50-year-old female is diagnosed with conventional high-grade chondrosarcoma of the proximal femur. Her multidisciplinary team opts for surgical resection rather than primary chemotherapy. What is the primary biological reason conventional chondrosarcoma is notoriously resistant to systemic chemotherapy?

. Rapid cellular turnover preventing drug accumulation
. Frequent p53 mutations altering apoptosis
. High expression of MDR-1 gene and poor vascularity of the cartilaginous matrix
. Extreme hypervascularity washing out chemotherapeutic agents
. Strict intracellular localization of the tumor cells

Correct Answer & Explanation

. High expression of MDR-1 gene and poor vascularity of the cartilaginous matrix

Explanation

Conventional chondrosarcomas are highly chemoresistant due to their poor vascularity, dense extracellular hyaline matrix that acts as a barrier, and high expression of the multidrug-resistance 1 (MDR-1) gene. Wide surgical excision remains the mainstay of treatment.

Question 1150

Topic: 10. Pathology and Oncology

A 25-year-old patient presents with a destructive lesion in the mandible. Histological examination reveals a unique bimorphic pattern consisting of islands of well-differentiated hyaline cartilage admixed with sheets of primitive, undifferentiated small round blue cells. What is the diagnosis?

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

Correct Answer & Explanation

. Mesenchymal chondrosarcoma

Explanation

Mesenchymal chondrosarcoma is an aggressive variant characterized by a bimorphic histological appearance featuring islands of benign-appearing cartilage mixed with highly cellular areas of small round blue cells. It frequently occurs in the jaw, ribs, and spine.

Question 1151

Topic: 10. Pathology and Oncology
A 65-year-old male with a history of an enlarging pelvic mass is diagnosed with a Grade II conventional chondrosarcoma of the right ilium (Zone I). No metastatic disease is identified. Which of the following is the most appropriate management?
. Intralesional curettage and cementation
. Neoadjuvant chemotherapy followed by curettage
. Radiation therapy alone
. Radiofrequency ablation
. Wide surgical resection

Correct Answer & Explanation

. Wide surgical resection

Explanation

The standard of care for intermediate and high-grade (Grade II/III) conventional chondrosarcomas of the pelvis is wide surgical resection (en bloc excision) to achieve negative margins. Curettage is generally reserved for low-grade appendicular tumors.

Question 1152

Topic: 10. Pathology and Oncology

A 70-year-old male presents with a large, destructive lesion in his distal femur. Biopsy reveals areas of low-grade cartilaginous tumor abruptly transitioning to a high-grade undifferentiated pleomorphic sarcoma. Which of the following accurately describes the treatment approach and prognosis for this patient?

. Intralesional curettage; excellent prognosis
. Wide surgical resection combined with multiagent chemotherapy; poor prognosis
. Definitive radiation therapy; intermediate prognosis
. Isolated limb perfusion; excellent prognosis
. Observation; indolent course

Correct Answer & Explanation

. Wide surgical resection combined with multiagent chemotherapy; poor prognosis

Explanation

Dedifferentiated chondrosarcoma is characterized by a low-grade cartilage tumor adjacent to a high-grade non-cartilaginous sarcoma. It is highly aggressive and treated similarly to osteosarcoma (wide resection + chemotherapy), but overall 5-year survival remains very poor (10-20%).

Question 1153

Topic: 10. Pathology and Oncology

A 40-year-old patient with Ollier disease develops a rapidly enlarging, painful mass in a previously asymptomatic enchondroma of the distal femur. Biopsy confirms central chondrosarcoma. Which of the following genetic mutations is most characteristic of both the precursor lesion and the subsequent malignancy?

. IDH1 and IDH2
. GNAS
. SH3BP2
. SOX9
. EXT1

Correct Answer & Explanation

. IDH1 and IDH2

Explanation

Mutations in the isocitrate dehydrogenase genes (IDH1 and IDH2) are found in the majority of central enchondromas and conventional central chondrosarcomas, including those associated with Ollier disease and Maffucci syndrome.

Question 1154

Topic: 10. Pathology and Oncology

Which of the following MRI findings is most highly predictive of a high-grade conventional chondrosarcoma as opposed to a low-grade atypical cartilaginous tumor/enchondroma?

. High signal intensity on T2-weighted images
. Lobulated growth pattern
. Peripheral and septal enhancement
. Punctate and rings-and-arcs calcifications
. Presence of a soft-tissue mass and extensive cortical destruction

Correct Answer & Explanation

. Presence of a soft-tissue mass and extensive cortical destruction

Explanation

While high T2 signal and lobulated architecture with peripheral/septal enhancement are characteristic of cartilaginous tumors in general, aggressive features like a soft-tissue mass, deep endosteal scalloping (>2/3 cortical thickness), and frank cortical destruction indicate a higher-grade malignancy.

Question 1155

Topic: 10. Pathology and Oncology

A 35-year-old male with a known solitary osteochondroma of the proximal tibia reports new-onset pain and an increase in the size of the mass. An MRI is ordered to evaluate for secondary chondrosarcoma. Which MRI finding of the cartilage cap is most concerning for malignant transformation?

. Cap thickness > 5 mm
. Absence of overlying bursa
. Cartilage cap thickness > 2 cm
. Continuity of the medullary canal
. Lack of peripheral enhancement

Correct Answer & Explanation

. Cartilage cap thickness > 2 cm

Explanation

In skeletally mature adults, a cartilage cap thickness greater than 2 cm on MRI is highly suspicious for malignant transformation of an osteochondroma into a secondary chondrosarcoma. Pain and interval growth are the classic clinical signs.

Question 1156

Topic: 10. Pathology and Oncology

A 60-year-old female with metastatic breast cancer presents with moderate thigh pain. Radiographs reveal a lytic lesion in the peritrochanteric region of the femur measuring 70% of the cortical diameter. Using Mirels' criteria, what is her score and the appropriate management recommendation?

. Score 6; Observation
. Score 8; Radiation therapy only
. Score 12; Immediate amputation
. Score 10; Prophylactic internal fixation
. Score 11; Observation

Correct Answer & Explanation

. Score 10; Prophylactic internal fixation

Explanation

Mirels' criteria score: Site (Lower limb = 2), Pain (Moderate = 2), Lesion (Lytic = 3), Size (>2/3 cortex = 3). Total score is 10. A score of 9 or greater indicates high risk for pathologic fracture, and prophylactic internal fixation is recommended.

Question 1157

Topic: 10. Pathology and Oncology

A 50-year-old male is incidentally found to have an enchondroma in the proximal humerus during an MRI for a rotator cuff tear. Which of the following is the most reliable clinical indicator suggesting possible malignant transformation to a chondrosarcoma?

. Incidental finding of "rings and arcs" on a radiograph
. Lesion size greater than 3 cm
. New-onset, unprovoked rest pain
. Presence of heavily calcified matrix
. Location in the small bones of the hands or feet

Correct Answer & Explanation

. New-onset, unprovoked rest pain

Explanation

The most sensitive and reliable clinical symptom of malignant transformation from an enchondroma to a chondrosarcoma is the development of new, unprovoked pain (rest or night pain) that is not attributable to other causes (like trauma or adjacent joint disease).

Question 1158

Topic: 10. Pathology and Oncology

What is the primary role of external beam radiation therapy in the treatment algorithm of conventional chondrosarcoma?

. Primary definitive treatment for all Grade I lesions
. Routine adjuvant therapy following wide surgical resection
. Neoadjuvant therapy to shrink the tumor prior to resection
. Alternative to amputation for large appendicular lesions
. Palliative treatment or definitive care for unresectable base-of-skull/axial lesions

Correct Answer & Explanation

. Palliative treatment or definitive care for unresectable base-of-skull/axial lesions

Explanation

Conventional chondrosarcoma is generally considered radioresistant. Radiation therapy is therefore reserved for palliative symptom control or as definitive treatment in locations where surgical resection with negative margins is impossible, such as the base of the skull or complex axial skeleton locations.

Question 1159

Topic: 10. Pathology and Oncology

A 35-year-old male with multiple hereditary exostoses presents with a rapidly enlarging mass over his posterior medial distal femur. MRI reveals an osteochondroma with a thickened cartilage cap. What is the accepted threshold for cartilage cap thickness on MRI that highly suggests malignant transformation to secondary chondrosarcoma?

. Greater than 0.5 cm
. Greater than 1.0 cm
. Greater than 2.0 cm
. Greater than 3.5 cm
. Greater than 5.0 cm

Correct Answer & Explanation

. Greater than 2.0 cm

Explanation

In adults, a cartilage cap thickness greater than 2.0 cm on MRI is highly suspicious for malignant transformation of an osteochondroma to a secondary chondrosarcoma. Wide surgical resection is indicated.

Question 1160

Topic: 10. Pathology and Oncology

A 42-year-old male presents with a painful, lytic lesion in the proximal humeral epiphysis. Histology reveals cells with abundant clear cytoplasm, distinct cytoplasmic borders, and interspersed hyaline cartilage. Because of its epiphyseal location, this malignant entity is most commonly misdiagnosed radiographically as which benign tumor?

. Giant cell tumor
. Chondroblastoma
. Aneurysmal bone cyst
. Enchondroma
. Osteoid osteoma

Correct Answer & Explanation

. Chondroblastoma

Explanation

Clear cell chondrosarcoma typically arises in the epiphysis of long bones, which frequently leads to radiographic misdiagnosis as a chondroblastoma. Unlike chondroblastoma, clear cell chondrosarcoma requires wide en bloc resection.

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