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10. Pathology and Oncology MCQs

Practice Set 262 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 5221

Topic: 10. Pathology and Oncology

Which of the following factors would most likely lead to consideration of amputation over limb salvage for an osteosarcoma of the distal femur?

. Patient request for amputation due to preference for prosthetic fitting.
. Tumor size greater than 15 cm.
. Infection of the primary tumor site.
. Pathological fracture that has extended beyond the soft tissue compartment.
. Poor response to neoadjuvant chemotherapy (less than 50% necrosis).

Correct Answer & Explanation

. Infection of the primary tumor site.

Explanation

Infection of the primary tumor site is a strong contraindication to limb salvage with endoprosthetic reconstruction, as the risk of prosthetic infection is exceedingly high and devastating. While tumor size, pathological fracture, and poor chemotherapy response are challenging factors that may make limb salvage more difficult or increase recurrence risk, they are not absolute contraindications in themselves. A patient's informed request for amputation is a valid reason, but the question asks what 'would most likely lead to consideration' by the surgeon due to clinical factors. An uncontainable pathological fracture can make limb salvage impossible due to inability to achieve wide margins. Poor response to chemotherapy is a poor prognostic factor, but limb salvage is still attempted if feasible.

Question 5222

Topic: Bone Tumors

What is the most effective imaging modality for detecting early pulmonary metastases in a patient undergoing surveillance for osteosarcoma?

. Plain chest X-ray
. CT scan of the chest
. MRI of the chest
. PET/CT scan
. Ultrasound of the chest

Correct Answer & Explanation

. CT scan of the chest

Explanation

A CT scan of the chest is the most effective and sensitive imaging modality for detecting early, small pulmonary metastases from osteosarcoma. Plain chest X-rays have poor sensitivity for small nodules. MRI and PET/CT can detect pulmonary nodules but are typically not used as the primary routine surveillance tool due to cost, accessibility, and artifact issues (MRI) or radiation dose (PET/CT for frequent use). Ultrasound has no role in detecting lung metastases.

Question 5223

Topic: 10. Pathology and Oncology

Which of the following describes the most common histological variant of osteosarcoma?

. Telangiectatic
. Chondroblastic
. Fibroblastic
. Osteoblastic
. Small cell

Correct Answer & Explanation

. Osteoblastic

Explanation

Osteoblastic osteosarcoma is the most common histological variant of conventional osteosarcoma, characterized by the production of abundant osteoid and immature bone matrix by malignant osteoblasts. Chondroblastic and fibroblastic variants are also common, reflecting the differentiation patterns of the tumor, but osteoblastic is the most frequent. Telangiectatic and small cell osteosarcomas are rarer variants.

Question 5224

Topic: Bone Tumors

What is the primary concern for a growing child undergoing limb salvage with a conventional, fixed-length endoprosthesis after resection of a distal femoral osteosarcoma?

. Risk of prosthetic loosening.
. Long-term infection risk.
. Development of significant limb length discrepancy.
. Lack of sensory feedback in the reconstructed limb.
. Poor cosmetic outcome.

Correct Answer & Explanation

. Development of significant limb length discrepancy.

Explanation

In a skeletally immature patient, a conventional, fixed-length endoprosthesis does not grow, while the contralateral limb continues to grow. This will inevitably lead to a significant limb length discrepancy over time, requiring multiple revision surgeries for lengthening or contralateral limb shortening. This is a major concern. Loosening and infection are risks for any endoprosthesis, but limb length discrepancy is specific to the growing child with a fixed implant. Lack of sensory feedback is common to all prostheses, and cosmetic outcome is a factor, but not the primary concern related to 'fixed-length' in a 'growing child'.

Question 5225

Topic: 10. Pathology and Oncology

Which of the following is considered an absolute contraindication to neoadjuvant chemotherapy in a patient diagnosed with osteosarcoma?

. Pathological fracture at presentation.
. Presence of pulmonary metastases.
. Patient age over 60 years.
. Severe pre-existing renal dysfunction.
. Tumor size greater than 10 cm.

Correct Answer & Explanation

. Severe pre-existing renal dysfunction.

Explanation

Severe pre-existing renal dysfunction is a significant contraindication to standard high-dose methotrexate chemotherapy, a cornerstone of osteosarcoma treatment, as methotrexate is primarily cleared by the kidneys and can cause severe nephrotoxicity. Cisplatin also has nephrotoxicity. Modifications or alternative regimens would be necessary. Pathological fracture or pulmonary metastases are not contraindications; rather, they influence the overall treatment strategy. Age over 60 may lead to dose adjustments due to comorbidities but is not an absolute contraindication. Tumor size influences surgical planning but not the need for chemotherapy.

Question 5226

Topic: Bone Tumors

A patient with a distal femoral osteosarcoma, initially treated with limb salvage, develops a local recurrence in the residual bone proximal to the endoprosthesis. What is the most appropriate next step in management?

. Systemic chemotherapy alone, as local recurrence is a sign of widespread disease.
. Palliative radiation therapy to the recurrence site.
. Surgical wide resection of the recurrence, possibly requiring amputation.
. Observation with serial imaging to assess growth rate.
. Intra-arterial chemotherapy to the limb.

Correct Answer & Explanation

. Surgical wide resection of the recurrence, possibly requiring amputation.

Explanation

Local recurrence of osteosarcoma, particularly if resectable, warrants aggressive surgical management, often involving a wider resection that may necessitate amputation if limb salvage is no longer feasible with adequate margins. While systemic therapy may be part of the overall plan, surgical removal of the recurrence offers the best chance for local control and potentially improved survival. Local recurrence is not always indicative of widespread disease and may still be curable. Palliative radiation might be considered if surgery is not an option, and observation is inappropriate for an aggressive recurrence.

Question 5227

Topic: 10. Pathology and Oncology

A 55-year-old male presents with a 6-month history of dull, aching pain in his left proximal humerus, not relieved by rest. Radiographs reveal a lytic lesion with punctate and ring-and-arc calcifications within the medullary cavity, associated with cortical thickening and periosteal reaction. Which of the following is the most appropriate initial management step?

. Observation with serial radiographs
. CT-guided core needle biopsy
. Wide en bloc resection
. Intralesional curettage
. Adjuvant radiation therapy

Correct Answer & Explanation

. CT-guided core needle biopsy

Explanation

The patient's age, insidious pain, and radiographic findings (lytic lesion with chondroid matrix calcifications, cortical thickening, and periosteal reaction) are highly suspicious for a chondrosarcoma, particularly a low-grade lesion. A CT-guided core needle biopsy is the most appropriate initial management step to confirm the diagnosis, grade the tumor, and guide definitive surgical planning. Observation is not appropriate given the suspicious features. Wide en bloc resection is the definitive treatment but should only be performed after a confirmed diagnosis. Intralesional curettage is inadequate for chondrosarcoma due to high recurrence rates. Adjuvant radiation is typically reserved for unresectable tumors or positive margins, not as an initial step.

Question 5228

Topic: 10. Pathology and Oncology

Which histological grade of conventional chondrosarcoma is associated with the highest metastatic potential?

. Grade 0 (benign enchondroma)
. Grade 1
. Grade 2
. Grade 3
. Dedifferentiated chondrosarcoma

Correct Answer & Explanation

. Grade 3

Explanation

Among conventional chondrosarcomas, Grade 3 lesions exhibit the highest metastatic potential. Dedifferentiated chondrosarcoma, while having an even worse prognosis due to its anaplastic component, is considered a distinct entity with a high-grade sarcoma component, not merely a 'Grade 4' conventional chondrosarcoma. Grade 0 is a benign enchondroma. Grade 1 and 2 have progressively increasing metastatic risk, but Grade 3 represents the highest risk within the conventional grading system.

Question 5229

Topic: 10. Pathology and Oncology

A 40-year-old female presents with a slowly growing, painful mass in her right ilium. Imaging reveals a large, lobulated lesion with internal calcifications arising from the bone. Biopsy confirms a Grade 2 chondrosarcoma. What is the most crucial principle in the surgical management of this tumor?

. Intralesional curettage to preserve bone stock
. Marginal excision to minimize morbidity
. Wide en bloc resection with clear margins
. Adjuvant chemotherapy followed by delayed surgery
. Preoperative radiation therapy to shrink the tumor

Correct Answer & Explanation

. Wide en bloc resection with clear margins

Explanation

Wide en bloc resection with clear surgical margins is the gold standard and most crucial principle in the surgical management of chondrosarcoma. These tumors are highly resistant to chemotherapy and radiation, making surgical extirpation the primary curative modality. Intralesional curettage or marginal excision is associated with high local recurrence rates. While adjuvant therapies might be considered in specific high-risk or positive margin cases, they are not the primary principle for initial surgical management, especially for a resectable Grade 2 lesion.

Question 5230

Topic: 10. Pathology and Oncology

Regarding the differentiation of an enchondroma from a low-grade central chondrosarcoma in an appendicular skeleton lesion, which of the following MRI features is most suggestive of chondrosarcoma?

. Lobulated morphology on T2-weighted images
. Calcified matrix within the lesion
. Cortical scalloping greater than 2/3 of cortical thickness
. High signal intensity on T2-weighted images
. Presence of fat signal within the lesion

Correct Answer & Explanation

. Cortical scalloping greater than 2/3 of cortical thickness

Explanation

Cortical scalloping greater than 2/3 of cortical thickness, or actual cortical breakthrough/destruction, is a strong indicator of a low-grade chondrosarcoma rather than an enchondroma. While lobulated morphology, calcified matrix, and high T2 signal can be seen in both, significant cortical erosion suggests aggressive behavior. Fat signal within the lesion would be more indicative of a benign fatty lesion or bone infarct.

Question 5231

Topic: 10. Pathology and Oncology

A 68-year-old male with Ollier's disease develops increasing pain and a palpable mass in his left femur. Radiographs show enlargement and increased mineralization of an existing enchondroma-like lesion. Which type of chondrosarcoma is he most likely to develop?

. Dedifferentiated chondrosarcoma
. Mesenchymal chondrosarcoma
. Conventional central chondrosarcoma
. Clear cell chondrosarcoma
. Juxtacortical chondrosarcoma

Correct Answer & Explanation

. Conventional central chondrosarcoma

Explanation

Patients with Ollier's disease (multiple enchondromatosis) have a significantly increased risk of developing conventional central chondrosarcoma, which arises from malignant transformation of one of their benign enchondromas. Dedifferentiated chondrosarcoma can arise from any conventional chondrosarcoma, but the primary transformation in Ollier's is typically to conventional central type. Mesenchymal, clear cell, and juxtacortical chondrosarcomas are distinct, rarer variants not specifically linked to Ollier's disease in this manner.

Question 5232

Topic: Bone Tumors

Which of the following is considered a poor prognostic indicator in conventional chondrosarcoma?

. Location in the appendicular skeleton
. Histological Grade 1
. Age less than 40 years
. Positive surgical margins
. Presence of 'popcorn' calcifications

Correct Answer & Explanation

. Positive surgical margins

Explanation

Positive surgical margins are a strong and consistent poor prognostic indicator, significantly increasing the risk of local recurrence and potentially metastasis. Location in the appendicular skeleton generally has a better prognosis than axial lesions. Grade 1 is low grade and has a good prognosis. Age less than 40 is typically associated with better prognosis in many cancers, though chondrosarcoma peaks later. 'Popcorn' calcifications are a radiographic feature consistent with chondroid matrix, not a prognostic indicator of malignancy.

Question 5233

Topic: 10. Pathology and Oncology

A 25-year-old male presents with a painful mass in his maxilla. Biopsy reveals small round cells with areas of cartilage formation and a hemangiopericytoma-like vascular pattern. What is the most likely diagnosis?

. Conventional chondrosarcoma Grade 1
. Mesenchymal chondrosarcoma
. Clear cell chondrosarcoma
. Dedifferentiated chondrosarcoma
. Chondroblastoma

Correct Answer & Explanation

. Mesenchymal chondrosarcoma

Explanation

The description of small round cells, areas of cartilage formation, and a hemangiopericytoma-like vascular pattern is pathognomonic for mesenchymal chondrosarcoma. This tumor frequently occurs in craniofacial bones, spine, and pelvis, and less commonly in long bones. Conventional chondrosarcomas have more classic chondroid matrix. Clear cell chondrosarcoma has polygonal cells with clear cytoplasm. Dedifferentiated chondrosarcoma shows a transition from conventional chondrosarcoma to a high-grade non-cartilaginous sarcoma. Chondroblastoma occurs in epiphyses and has characteristic 'chicken wire' calcifications.

Question 5234

Topic: 10. Pathology and Oncology

A 50-year-old patient undergoes wide en bloc resection for a Grade 2 conventional chondrosarcoma of the proximal femur. Postoperative MRI at 6 months shows no evidence of local recurrence. What is the most appropriate long-term follow-up strategy?

. No further imaging is needed if the patient is asymptomatic.
. Annual chest X-ray for 5 years, then biannually.
. CT scan of the chest, abdomen, and pelvis every 6 months for 2 years, then annually.
. MRI of the local site and chest X-ray every 6-12 months for 5-10 years.
. Bone scan every year indefinitely.

Correct Answer & Explanation

. MRI of the local site and chest X-ray every 6-12 months for 5-10 years.

Explanation

Follow-up for resected chondrosarcoma, especially Grade 2 or higher, typically involves surveillance for both local recurrence and distant metastases. Lung is the most common site of metastasis. MRI of the local site to detect recurrence and CT chest to detect lung metastases are standard. For a Grade 2 chondrosarcoma, aggressive surveillance is warranted, usually involving MRI of the local site and chest imaging (CT is more sensitive than X-ray) every 6-12 months for several years, then yearly. CT of the abdomen/pelvis may be included for large axial tumors, but chest is paramount. Option 3 is the most comprehensive and appropriate given the tumor grade. Option 2 is insufficient. Option 1 is negligent. Option 5 is not the primary imaging for metastasis.

Question 5235

Topic: 10. Pathology and Oncology

Which of the following genetic mutations is most commonly associated with central chondrosarcoma?

. TP53
. IDH1/IDH2
. MYC amplification
. TERT promoter mutations
. H3F3A

Correct Answer & Explanation

. IDH1/IDH2

Explanation

Mutations in Isocitrate Dehydrogenase 1 and 2 (IDH1/IDH2) are found in a significant proportion (approximately 50-70%) of central enchondromas and conventional central chondrosarcomas (Grades 1 and 2). They are considered early events in chondrosarcoma development. While other mutations can occur, IDH mutations are the most commonly identified and diagnostically relevant in central chondrosarcomas. TP53 is more associated with high-grade sarcomas generally. MYC and TERT are found in some aggressive tumors but are not as common or specific as IDH mutations in central chondrosarcoma.

Question 5236

Topic: 10. Pathology and Oncology

A 70-year-old male with a history of multiple osteochondromas (Hereditary Multiple Exostoses) presents with increasing pain in a previously asymptomatic lesion on his distal femur. Radiographs show a thickened cartilaginous cap exceeding 2 cm. What is the most appropriate next step?

. NSAIDs and observation
. CT-guided biopsy of the cartilaginous cap
. Excision of the osteochondroma with its cartilaginous cap
. Systemic chemotherapy
. Radiation therapy

Correct Answer & Explanation

. Excision of the osteochondroma with its cartilaginous cap

Explanation

In a patient with Hereditary Multiple Exostoses, an increase in pain and a cartilaginous cap thickness exceeding 2 cm (or 1 cm in adults generally) on an osteochondroma are highly suspicious for malignant transformation into a secondary peripheral chondrosarcoma. Therefore, surgical excision of the entire osteochondroma, including its cartilaginous cap and underlying stalk, with wide margins, is the recommended treatment, provided it is resectable. A biopsy could be considered but excision is often definitive and diagnostic. NSAIDs and observation are inappropriate given the high suspicion. Chemotherapy and radiation are generally ineffective for chondrosarcoma.

Question 5237

Topic: Bone Tumors

Which variant of chondrosarcoma is characterized by bland chondrocytes with clear cytoplasm, typically arising in the epiphysis or epiphyseal equivalent of long bones?

. Conventional central chondrosarcoma
. Dedifferentiated chondrosarcoma
. Clear cell chondrosarcoma
. Mesenchymal chondrosarcoma
. Juxtacortical chondrosarcoma

Correct Answer & Explanation

. Clear cell chondrosarcoma

Explanation

Clear cell chondrosarcoma is a rare, low-grade variant that typically arises in the epiphysis or apophysis of long bones (e.g., proximal humerus, distal femur) and is characterized histologically by cells with clear cytoplasm, often resembling chondroblastoma, but with infiltrative growth. Conventional central chondrosarcoma is medullary. Dedifferentiated has a high-grade non-cartilaginous component. Mesenchymal has small round cells. Juxtacortical arises on the surface of the bone.

Question 5238

Topic: 10. Pathology and Oncology

A 45-year-old male presents with a large, destructive mass in his sacrum, causing neurological symptoms. Biopsy reveals a Grade 3 chondrosarcoma. What is the biggest challenge in treating this specific presentation?

. Resistance to chemotherapy
. High metastatic potential
. Achieving wide surgical margins
. Difficulty in histological grading
. Lack of suitable prosthetic reconstruction options

Correct Answer & Explanation

. Achieving wide surgical margins

Explanation

The biggest challenge in treating sacral chondrosarcomas, especially large, destructive, or high-grade lesions, is achieving wide surgical margins without causing unacceptable neurological deficit (e.g., bowel/bladder dysfunction, lower extremity weakness). While chondrosarcomas are resistant to chemotherapy and have metastatic potential (especially Grade 3), the anatomical constraints of the sacrum make radical resection extremely difficult, often resulting in marginal or intralesional excisions with high local recurrence rates. Histological grading is typically possible. Reconstruction is complex but secondary to achieving adequate margins.

Question 5239

Topic: 10. Pathology and Oncology

A 60-year-old patient with a known enchondroma in the distal femur presents with new onset of dull pain. MRI shows growth of the lesion, cortical erosion, and soft tissue extension. Biopsy confirms Grade 2 chondrosarcoma. What surgical approach would be most appropriate?

. Intralesional curettage with adjuvant cryosurgery
. Marginal excision using a periosteal stripping technique
. Wide en bloc resection preserving the joint
. Amputation at the hip level
. Preoperative radiation followed by curettage

Correct Answer & Explanation

. Wide en bloc resection preserving the joint

Explanation

For a resectable Grade 2 chondrosarcoma of the distal femur with soft tissue extension, wide en bloc resection is the standard of care. This approach aims to achieve clear surgical margins, which is paramount for local control. Joint preservation is highly desirable if oncologically sound. Amputation is reserved for extensive, unresectable tumors or failures of limb salvage. Intralesional curettage and marginal excision are inadequate for Grade 2 chondrosarcoma and carry high recurrence rates. Radiation is not typically effective as a primary neoadjuvant therapy for conventional chondrosarcoma.

Question 5240

Topic: 10. Pathology and Oncology

Which of the following is characteristic of dedifferentiated chondrosarcoma?

. Presence of IDH1/2 mutations in the dedifferentiated component
. Typically arises from previously irradiated bone
. Composed of two distinct components: low-grade chondrosarcoma and high-grade non-cartilaginous sarcoma
. Excellent prognosis with intralesional curettage
. Metastasizes primarily to regional lymph nodes

Correct Answer & Explanation

. Composed of two distinct components: low-grade chondrosarcoma and high-grade non-cartilaginous sarcoma

Explanation

Dedifferentiated chondrosarcoma is characterized by the abrupt juxtaposition of a well-differentiated conventional chondrosarcoma component (often Grade 1) with a high-grade, non-cartilaginous sarcoma component (e.g., osteosarcoma, fibrosarcoma, undifferentiated pleomorphic sarcoma). This biphasic morphology is key. It carries a poor prognosis. IDH mutations are typically found in the chondrosarcoma component, not necessarily the dedifferentiated component. It does not typically arise from irradiated bone and metastasizes hematogenously, primarily to the lungs, not regional lymph nodes. Intralesional curettage is absolutely contraindicated due to its high-grade nature and poor prognosis.

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