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10. Pathology and Oncology MCQs

Practice Set 266 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 5301

Topic: Bone Tumors

For enchondromas in high-risk locations (e.g., long bones in older patients) where differentiation from low-grade chondrosarcoma is challenging, what modification to standard curettage might be considered?

. Adjuvant radiation therapy
. En bloc resection
. Extended curettage with adjuvant therapy (e.g., cryoablation or phenol)
. Systemic chemotherapy
. Prophylactic amputation

Correct Answer & Explanation

. Extended curettage with adjuvant therapy (e.g., cryoablation or phenol)

Explanation

In cases where there is a higher suspicion of low-grade chondrosarcoma, or to reduce the risk of recurrence in borderline lesions, extended curettage combined with a local adjuvant therapy (such as cryoablation, phenol, or argon beam coagulation) is often performed. These adjuvants help to destroy any residual microscopic tumor cells in the cavity walls, effectively expanding the margins of the intralesional resection. En bloc resection is typically reserved for higher-grade chondrosarcomas. Radiation and chemotherapy are not standard for low-grade chondrosarcomas or enchondromas.

Question 5302

Topic: 10. Pathology and Oncology

What is the primary utility of a PET scan in the workup of a known enchondroma?

. To assess bone mineral density
. To differentiate benign from malignant chondroid lesions
. To evaluate vascularity of the lesion
. To stage distant metastases
. To identify pathological fractures

Correct Answer & Explanation

. To differentiate benign from malignant chondroid lesions

Explanation

PET/CT, using FDG, can be helpful in differentiating benign enchondromas from low-grade chondrosarcomas. Malignant chondroid tumors tend to have higher metabolic activity and will show increased FDG uptake, whereas benign enchondromas typically show little to no uptake. However, there can be overlap, especially with highly active enchondromas or very low-grade chondrosarcomas.

Question 5303

Topic: 10. Pathology and Oncology

When evaluating for subtle cortical breach or extension into soft tissue in a suspected chondroid tumor, which imaging modality is generally preferred?

. Plain radiographs
. CT scan
. MRI
. Ultrasound
. Bone scan

Correct Answer & Explanation

. MRI

Explanation

MRI is superior to CT for assessing soft tissue involvement, marrow invasion, and subtle cortical breach due to its excellent soft tissue contrast resolution. While CT is good for cortical details and calcifications, MRI provides more comprehensive information regarding the extent of the lesion and its relationship to surrounding structures.

Question 5304

Topic: Bone Tumors

A young patient presents with multiple cartilaginous lesions in their long bones. Which of the following conditions is least likely to be in the differential diagnosis?

. Ollier's disease
. Maffucci's syndrome
. Multiple osteochondromatosis
. Fibrous dysplasia
. Metachondromatosis

Correct Answer & Explanation

. Fibrous dysplasia

Explanation

Fibrous dysplasia is a fibro-osseous lesion characterized by immature woven bone within a fibrous stroma, often appearing as a 'ground-glass' lesion, not primarily cartilaginous. The other conditions (Ollier's disease, Maffucci's syndrome, multiple osteochondromatosis, and metachondromatosis) all involve multiple cartilaginous lesions or cartilage-capped bony exostoses and would be appropriate differentials.

Question 5305

Topic: 10. Pathology and Oncology

The presence of a periosteal reaction associated with an intramedullary cartilaginous lesion is concerning for:

. Healing fracture
. Benign enchondroma
. Low-grade chondrosarcoma
. Non-ossifying fibroma
. Bone infarct

Correct Answer & Explanation

. Low-grade chondrosarcoma

Explanation

While periosteal reaction can occur with a fracture through an enchondroma, anintactintramedullary cartilaginous lesion exhibiting a periosteal reaction is a significant radiographic red flag for malignancy, specifically a low-grade chondrosarcoma. It suggests cortical irritation or impending cortical breach due to aggressive growth, which is not characteristic of a benign, quiescent enchondroma.

Question 5306

Topic: 10. Pathology and Oncology

A 25-year-old male has an incidental 3 cm chondroid lesion in his distal femur, clearly benign on radiographs and MRI. He is asymptomatic. What is the most appropriate next step?

. Observation with no further imaging
. Surgical biopsy
. Curettage and bone grafting
. Annual MRI for 5 years
. Annual X-rays for 2-3 years

Correct Answer & Explanation

. Annual X-rays for 2-3 years

Explanation

For an asymptomatic, radiographically benign enchondroma in a long bone, observation with serial plain radiographs (typically annually for 2-3 years) is appropriate to monitor for any subtle changes in size, cortical integrity, or development of symptoms. Aggressive imaging like annual MRI is generally overkill for a clearly benign lesion, and biopsy or surgery is not indicated in the absence of symptoms or suspicious features.

Question 5307

Topic: 10. Pathology and Oncology

Enchondromas typically originate from rests of cartilage within the metaphysis, but can extend into the diaphysis. This explains their common location in the:

. Epiphysis
. Joint space
. Metadiaphysis
. Periosteum
. Subchondral bone

Correct Answer & Explanation

. Metadiaphysis

Explanation

Enchondromas are intramedullary cartilaginous tumors believed to arise from displaced rests of growth plate cartilage within the bone. As such, they are classically found in the metaphysis or extend into the diaphysis, thus commonly described as metadiaphyseal lesions. They are not typically epiphyseal (chondroblastoma is) or periosteal.

Question 5308

Topic: 10. Pathology and Oncology

Which of the following statements regarding the growth of a solitary enchondroma is generally true?

. They typically grow rapidly, doubling in size every 6 months
. They continue to grow aggressively throughout adulthood
. They usually stabilize in size after skeletal maturity
. Growth suggests malignant transformation in all cases
. They are always present at birth

Correct Answer & Explanation

. They usually stabilize in size after skeletal maturity

Explanation

Benign solitary enchondromas generally stabilize in size or grow very slowly after skeletal maturity. Significant growth in an adult enchondroma is a concerning sign and should prompt further investigation for potential malignant transformation to chondrosarcoma. They are not always present at birth and do not typically grow rapidly like aggressive tumors.

Question 5309

Topic: Bone Tumors

A 7-year-old child presents with an asymptomatic solitary lytic lesion in the metaphysis of the distal femur. There are no calcifications. Which of the following is less likely to be the diagnosis compared to an enchondroma, given the absence of calcifications?

. Non-ossifying fibroma
. Unicameral bone cyst
. Aneurysmal bone cyst
. Enchondroma
. Fibrous cortical defect

Correct Answer & Explanation

. Enchondroma

Explanation

While some enchondromas can be purely lytic, the classic radiographic feature of an enchondroma is the presence of punctate or rings-and-arcs calcifications within the cartilaginous matrix. In a child, a solitary purely lytic lesion in the metaphysis without calcifications would more commonly suggest diagnoses like a non-ossifying fibroma, unicameral bone cyst, aneurysmal bone cyst, or fibrous cortical defect. Therefore, enchondroma is less likely in this specific scenario due to the absence of its typical calcifications.

Question 5310

Topic: 10. Pathology and Oncology

Which of the following clinical presentations most strongly suggests a chondrosarcoma rather than a benign enchondroma?

. Painless swelling in the small bone of the hand
. Incidental finding on X-ray
. New onset of constant, dull pain in a large long bone in a 55-year-old
. Pathological fracture in a phalanx
. Lesion with punctate calcifications in a 20-year-old

Correct Answer & Explanation

. New onset of constant, dull pain in a large long bone in a 55-year-old

Explanation

New onset of constant, dull, increasing pain in an intramedullary chondroid lesion, particularly in a large long bone of an older adult, is the most concerning symptom for malignant transformation to chondrosarcoma. Enchondromas are typically asymptomatic unless complicated by fracture. Painless swelling or incidental findings are less specific, and while pathological fractures can occur in benign enchondromas, new, unremitting pain is a more direct indicator of a biologically active, potentially malignant lesion.

Question 5311

Topic: 10. Pathology and Oncology

When using adjuvant cryoablation during extended curettage for chondroid lesions, what is the primary goal?

. To promote osteogenesis
. To enhance bone graft integration
. To sterilize the tumor bed and kill residual tumor cells
. To reduce post-operative pain
. To reduce surgical bleeding

Correct Answer & Explanation

. To sterilize the tumor bed and kill residual tumor cells

Explanation

The primary goal of adjuvant therapy like cryoablation (or phenol, argon beam) used during extended curettage is to destroy any microscopic residual tumor cells that may have been left behind in the tumor cavity walls, thereby minimizing the risk of local recurrence. It acts as a local cytotoxic agent to sterilize the tumor bed, particularly in cases where differentiation between benign and low-grade malignant is challenging or in aggressive benign lesions.

Question 5312

Topic: 10. Pathology and Oncology

A patient presenting with multifocal enchondromas, particularly if unilateral and deforming, should be carefully screened for complications including:

. Premature closure of growth plates
. Pathological fractures
. Short stature
. Malignant transformation
. All of the above

Correct Answer & Explanation

. All of the above

Explanation

Conditions like Ollier's disease (multifocal enchondromatosis) can lead to a variety of complications including limb length discrepancies due to premature or asymmetric growth plate arrest, angular deformities, pathological fractures (due to weakened bone), and a significantly increased risk of malignant transformation to chondrosarcoma. Therefore, screening for all these complications is essential.

Question 5313

Topic: 10. Pathology and Oncology

While sporadic enchondromas are often associated with IDH1/IDH2 mutations, Ollier's disease is frequently linked to somatic mosaic mutations in which gene?

. PTPN11
. ACVR1
. EXT1/EXT2
. IDH1/IDH2
. GNAS

Correct Answer & Explanation

. IDH1/IDH2

Explanation

Ollier's disease, like solitary enchondromas and central low-grade chondrosarcomas, is strongly associated with somatic mosaic mutations in IDH1 and IDH2 genes. This suggests a common molecular pathway for these cartilaginous tumors, with the mosaicism explaining the multifocal and often unilateral distribution in Ollier's. EXT1/EXT2 mutations are linked to multiple osteochondromatosis.

Question 5314

Topic: 10. Pathology and Oncology

Among benign cartilaginous bone tumors, which of the following is most common to be found as a solitary lesion within the intramedullary cavity?

. Chondroblastoma
. Osteochondroma
. Enchondroma
. Chondromyxoid fibroma
. Periosteal chondroma

Correct Answer & Explanation

. Enchondroma

Explanation

Enchondroma is the most common benign intramedullary cartilaginous tumor. Osteochondroma, while the most common benign bone tumor overall, is an exostosis (surface lesion) rather than intramedullary. Chondroblastoma is a rare benign cartilaginous tumor typically found in the epiphysis. Chondromyxoid fibroma and periosteal chondroma are much rarer than enchondroma.

Question 5315

Topic: 10. Pathology and Oncology

The continued growth of enchondromas in conditions like Ollier's disease after skeletal maturity is believed to be due to:

. Persistent activity of mutated growth factor receptors
. Disrupted apoptosis pathways in chondrocytes
. Increased vascularization of the lesions
. Activation of osteoclastic activity
. Chronic inflammation

Correct Answer & Explanation

. Disrupted apoptosis pathways in chondrocytes

Explanation

In conditions like Ollier's disease and Maffucci's syndrome, the enchondromas often continue to grow even after skeletal maturity. This is linked to the underlying IDH1/IDH2 mutations, which lead to an accumulation of D-2-hydroxyglutarate (D-2-HG). This oncometabolite disrupts normal chondrocyte differentiation and metabolism, leading to persistent proliferation and impaired apoptosis of the chondrocytes, thereby facilitating continued tumor growth.

Question 5316

Topic: 10. Pathology and Oncology

A 65-year-old patient presents with a several-month history of worsening, dull, persistent pain in their proximal femur. Radiographs show an intramedullary lesion with internal calcifications. What is the most critical next step in their workup?

. Immediate open biopsy
. MRI with contrast
. Bone scan
. Observation with NSAIDs
. Prophylactic fixation

Correct Answer & Explanation

. MRI with contrast

Explanation

In an older patient with new, worsening pain associated with a chondroid lesion in a large long bone, suspicion for chondrosarcoma is high. An MRI with contrast is the most critical next step. It provides detailed information about the lesion's extent, marrow involvement, cortical integrity, soft tissue extension, and enhancement characteristics, which are crucial for differentiating a benign enchondroma from a low-grade chondrosarcoma. This information then guides the planning of a biopsy and definitive treatment.

Question 5317

Topic: 10. Pathology and Oncology

When planning surgery for a Stage IIB osteosarcoma, which surgical margin is generally considered the minimum acceptable to achieve local control, assuming good response to neoadjuvant chemotherapy?

. Intralesional
. Marginal
. Wide
. Radical
. Palliative

Correct Answer & Explanation

. Wide

Explanation

For high-grade malignant tumors like Stage IIB osteosarcoma, a wide surgical margin is the standard goal to achieve local control. This aims for a microscopically negative margin through healthy tissue outside the reactive zone. Intralesional or marginal excisions have unacceptably high local recurrence rates for high-grade sarcomas. Radical excision is often reserved for situations where wide margins are difficult to achieve safely (e.g., specific anatomical locations) or for very large, extensive tumors.

Question 5318

Topic: 10. Pathology and Oncology
According to Enneking's staging, a musculoskeletal sarcoma with distant metastases, regardless of grade or local extent, falls into which stage?
. Stage IA
. Stage IIB
. Stage III
. Stage IV
. Metastatic disease is not part of Enneking's system

Correct Answer & Explanation

. Stage III

Explanation

Any malignant tumor with distant metastases (M1) is automatically classified as Stage III in the Enneking system, regardless of its grade (G) or local extent (T). Metastatic disease significantly impacts prognosis and treatment strategy.

Question 5319

Topic: 10. Pathology and Oncology

A patient with a Stage 3 (Aggressive) benign tumor, such as an aggressive giant cell tumor with pathological fracture and significant soft tissue extension, typically requires which type of surgical margin?

. Intralesional curettage
. Marginal excision
. Wide excision
. Palliative debulking
. Observation only

Correct Answer & Explanation

. Wide excision

Explanation

Stage 3 benign tumors exhibit aggressive local growth, often with cortical destruction, soft tissue extension, and high local recurrence rates if treated with intralesional or marginal methods. Therefore, a wide excision, aiming for clear margins through healthy tissue, is often necessary to achieve local control for these aggressive benign lesions, similar to low-grade malignancies.

Question 5320

Topic: 10. Pathology and Oncology

Which factor is NOT included in the Enneking Musculoskeletal Tumor Society (MSTS) staging system for malignant tumors?

. Histological grade (G)
. Local extent (T)
. Presence of regional lymph node involvement
. Presence of distant metastases (M)
. All of the above are included

Correct Answer & Explanation

. All of the above are included

Explanation

The Enneking MSTS staging system for malignant tumors uses Grade (G), Local Extent (T), and Metastasis (M). It does not explicitly include regional lymph node involvement as a primary staging criterion for sarcomas, unlike carcinomas. While lymph node metastases can occur, they are generally rare in sarcomas and, if present, would fall under M1 (distant metastasis).

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