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10. Pathology and Oncology MCQs

Practice Set 265 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 5281

Topic: 10. Pathology and Oncology

Regarding the biological behavior of chondrosarcoma, what distinguishes it from most other primary bone sarcomas (e.g., osteosarcoma, Ewing sarcoma)?

. Rapid systemic spread and early metastasis
. High sensitivity to chemotherapy and radiation therapy
. Predominantly affects pediatric and adolescent populations
. Often presents as a low-grade tumor with slow growth and primarily local recurrence risk
. Metastasizes primarily to regional lymph nodes

Correct Answer & Explanation

. Often presents as a low-grade tumor with slow growth and primarily local recurrence risk

Explanation

Chondrosarcoma, particularly the conventional type, often presents as a low-grade tumor with a relatively slow growth rate. Its primary risk is local recurrence if not adequately resected with wide margins. While higher grades can metastasize, its general behavior is less aggressive than osteosarcoma or Ewing sarcoma, which are typically high-grade, rapidly spreading, and responsive to neoadjuvant therapy. Chondrosarcoma also affects adults more commonly and rarely metastasizes to lymph nodes.

Question 5282

Topic: 10. Pathology and Oncology

A 70-year-old patient with Paget's disease of bone develops a rapidly enlarging, painful mass in a previously affected bone. Biopsy reveals a high-grade pleomorphic sarcoma with areas of focal cartilaginous differentiation. What is the most likely diagnosis?

. Conventional chondrosarcoma Grade 3
. Mesenchymal chondrosarcoma
. Dedifferentiated chondrosarcoma
. Paget's sarcoma (osteosarcoma variant)
. Clear cell chondrosarcoma

Correct Answer & Explanation

. Paget's sarcoma (osteosarcoma variant)

Explanation

Malignant transformation of Paget's disease most commonly results in osteosarcoma (often referred to as Paget's sarcoma), but can rarely also result in fibrosarcoma or chondrosarcoma. The description of a rapidly enlarging, painful mass with a high-grade pleomorphic sarcoma and focal cartilaginous differentiation (Paget's sarcoma can have chondroblastic features) is highly suggestive of a Paget's sarcoma, often an osteosarcoma or a related high-grade sarcoma. While dedifferentiated chondrosarcoma is possible, the strong association with Paget's disease points to Paget's sarcoma as the most direct diagnosis in this context.

Question 5283

Topic: 10. Pathology and Oncology

Which of the following is the most important factor in determining the prognosis of conventional chondrosarcoma?

. Patient age
. Tumor size
. Histological grade
. Location of the tumor (axial vs. appendicular)
. Duration of symptoms

Correct Answer & Explanation

. Histological grade

Explanation

The histological grade (Grade 1, 2, or 3) is the single most important factor in determining the prognosis of conventional chondrosarcoma, directly correlating with metastatic potential and overall survival. While tumor size and location (especially axial vs. appendicular) do impact management and can influence prognosis, the grade is paramount in predicting biological behavior.

Question 5284

Topic: 10. Pathology and Oncology

What is the primary imaging modality for local staging of a chondrosarcoma in an appendicular bone, specifically to assess soft tissue extension and intramedullary involvement?

. Plain X-ray
. Computed Tomography (CT)
. Magnetic Resonance Imaging (MRI)
. Bone Scintigraphy
. Ultrasound

Correct Answer & Explanation

. Magnetic Resonance Imaging (MRI)

Explanation

Magnetic Resonance Imaging (MRI) is the gold standard for local staging of bone sarcomas, including chondrosarcoma, due to its excellent soft tissue contrast. It accurately delineates tumor margins, intramedullary extent, neurovascular involvement, and soft tissue extension. While X-ray and CT provide bony detail, they are inferior for soft tissue evaluation. Bone scintigraphy assesses metabolic activity. Ultrasound has limited utility for intraosseous lesions.

Question 5285

Topic: Bone Tumors

A 50-year-old patient with a history of corticosteroid use presents with hip pain. Radiographs show a lucent lesion with central calcifications in the femoral head. On MRI, the lesion has a "double-rim" sign. This feature is most characteristic of:

. Enchondroma
. Low-grade chondrosarcoma
. Bone infarct
. Giant cell tumor
. Aneurysmal bone cyst

Correct Answer & Explanation

. Bone infarct

Explanation

The "double-rim" sign on MRI (a low signal intensity outer rim and a high signal intensity inner rim on T2-weighted images) is pathognomonic for osteonecrosis or bone infarct. Central calcifications can sometimes be seen within a bone infarct, which can be in the differential for a calcified intramedullary lesion, but the MRI features are distinct. Enchondromas generally do not present with this sign.

Question 5286

Topic: 10. Pathology and Oncology
A 60-year-old male presents with dull, constant pain in his distal femur. Radiographs show a 4 cm intramedullary lesion with a lobulated contour, speckled calcifications, and mild endosteal scalloping (<1/3 cortical thickness). A recent MRI shows no clear cortical breach or soft tissue mass, but increased tracer uptake on bone scan compared to previous studies. What is the most appropriate next step?
. Continued observation with annual X-rays
. PET scan for metabolic activity
. Open biopsy
. Prophylactic internal fixation
. Radiation therapy

Correct Answer & Explanation

. Open biopsy

Explanation

New onset or worsening pain in a chondroid lesion, especially in a long bone of an older patient, coupled with increased tracer uptake on a bone scan (suggesting metabolic activity), are concerning signs for malignant transformation to chondrosarcoma, even if other radiographic features are subtle. A definitive diagnosis requires a biopsy (either open or image-guided core biopsy if sufficient tissue can be obtained) to assess the histology and grade the tumor.

Question 5287

Topic: 10. Pathology and Oncology

What is a potential limitation of intralesional curettage for enchondromas, particularly in the long bones?

. High risk of malignant transformation post-procedure
. Inability to obtain sufficient tissue for diagnosis
. High recurrence rate if inadequate curettage
. Increased risk of pathological fracture after procedure
. Extensive blood loss

Correct Answer & Explanation

. High recurrence rate if inadequate curettage

Explanation

The main limitation and most common complication of intralesional curettage for enchondromas is local recurrence, particularly if the curettage is incomplete and microscopic cartilaginous nests are left behind. Malignant transformation is not induced by the procedure. Curettage provides ample tissue for diagnosis. While a temporary weakening of the bone occurs, pathological fracture risk is generally lower than if left untreated or in some other tumor types.

Question 5288

Topic: 10. Pathology and Oncology

Following successful curettage and bone grafting of an enchondroma, what is the typical recommended radiographic follow-up schedule?

. Monthly X-rays for 1 year
. Annually for 5 years, then as needed
. No further follow-up if asymptomatic
. CT scan every 6 months
. PET scan annually

Correct Answer & Explanation

. Annually for 5 years, then as needed

Explanation

After curettage and bone grafting of an enchondroma, long-term radiographic follow-up is generally recommended to monitor for recurrence or malignant transformation. A common protocol involves annual radiographs for approximately 5 years, and then as needed based on clinical symptoms or any suspicious findings. More frequent imaging or advanced modalities are typically reserved for symptomatic lesions or those with concerning features.

Question 5289

Topic: 10. Pathology and Oncology

An enchondroma-like lesion in which of the following locations carries the highest intrinsic risk of being a low-grade chondrosarcoma, even if radiographically benign-appearing?

. Phalanges of the hand
. Distal femur
. Proximal humerus
. Pelvis
. Distal tibia

Correct Answer & Explanation

. Pelvis

Explanation

Chondroid lesions in the axial skeleton (pelvis, scapula, sternum, ribs) and proximal long bones (femur, humerus) carry a higher intrinsic risk of being a low-grade chondrosarcoma compared to those in the small bones of the hands and feet or more distal long bones, even when imaging features appear benign. Lesions in the pelvis, in particular, are notorious for challenging differentiation and a higher index of suspicion for malignancy is warranted.

Question 5290

Topic: 10. Pathology and Oncology

What is the primary purpose of bone grafting after curettage of an enchondroma?

. To induce malignant transformation
. To prevent infection
. To restore structural integrity and promote healing
. To serve as a marker for future biopsies
. To stimulate immune response

Correct Answer & Explanation

. To restore structural integrity and promote healing

Explanation

After intralesional curettage of an enchondroma, a cavity remains. Bone grafting (autograft or allograft) is performed to fill this defect, provide structural support to the bone, and create a scaffold for new bone formation, thereby promoting healing and reducing the risk of pathological fracture. It does not induce malignancy, prevent infection (though careful aseptic technique is vital), or serve as a biopsy marker.

Question 5291

Topic: Bone Tumors

A purely lytic, expansile lesion without internal calcifications in the metadiaphysis of a long bone would make enchondroma less likely and raise suspicion for what differential?

. Fibrous dysplasia
. Non-ossifying fibroma
. Aneurysmal bone cyst
. Osteoid osteoma
. Bone infarct

Correct Answer & Explanation

. Aneurysmal bone cyst

Explanation

Enchondromas typically contain chondroid matrix calcifications, though occasionally they can be purely lytic. However, a purely lytic, expansile lesion, especially without internal calcifications, makes enchondroma less likely. An aneurysmal bone cyst (ABC) is a strong differential for such a presentation, often being expansile and purely lytic. Fibrous dysplasia typically has a 'ground-glass' matrix. Non-ossifying fibroma and osteoid osteoma have characteristic appearances, but are not usually expansile in this manner without calcifications as the primary distinguishing factor. Bone infarcts often have calcified rims or serpiginous patterns.

Question 5292

Topic: 10. Pathology and Oncology

A key characteristic distinguishing Ollier's disease from solitary enchondroma is:

. Presence of soft tissue hemangiomas
. Unilateral distribution of lesions
. Predominance in the appendicular skeleton
. Higher risk of pathological fracture
. Significantly lower risk of malignant transformation

Correct Answer & Explanation

. Unilateral distribution of lesions

Explanation

Ollier's disease is characterized by multiple enchondromas, typically with an asymmetric or unilateral distribution affecting the long bones. This distinguishes it from solitary enchondroma, which is a single lesion. The presence of soft tissue hemangiomas is characteristic of Maffucci's syndrome. While Ollier's disease does have a higher risk of pathological fracture and malignant transformation compared to solitary enchondromas, the multifocal, often unilateral presentation is the defining diagnostic characteristic.

Question 5293

Topic: 10. Pathology and Oncology

While enchondromas are often asymptomatic, what is the most common cause of pain when it does occur in the absence of malignant transformation?

. Nerve impingement
. Rapid growth
. Pathological microfracture
. Joint effusion
. Infection

Correct Answer & Explanation

. Pathological microfracture

Explanation

When an enchondroma becomes symptomatic without evidence of malignant transformation, the most common cause of pain is pathological microfractures or small stress fractures through the weakened bone within or surrounding the lesion. These microfractures can be precipitated by minor trauma or repetitive stress. Rapid growth, nerve impingement, or joint effusion are less common causes of pain for an uncomplicated benign enchondroma.

Question 5294

Topic: 10. Pathology and Oncology

Enchondromas in children, especially in the hands and feet, are typically managed with what approach if asymptomatic?

. Surgical excision due to high growth potential
. Observation and serial radiographs
. Radiation therapy
. Growth hormone inhibitors
. Biopsy regardless of symptoms

Correct Answer & Explanation

. Observation and serial radiographs

Explanation

Similar to adults, asymptomatic, radiographically benign enchondromas in children are typically managed with observation and serial radiographs. Surgical intervention is usually reserved for symptomatic lesions, those causing deformity, or with suspicious features. The risk of malignant transformation in solitary enchondromas is very low in children.

Question 5295

Topic: 10. Pathology and Oncology

Which imaging modality is generally superior for visualizing the chondroid matrix calcifications within an enchondroma?

. Ultrasound
. MRI
. CT
. Nuclear bone scan
. Plain X-ray

Correct Answer & Explanation

. CT

Explanation

Computed Tomography (CT) is superior for detecting and characterizing subtle calcifications within a lesion, as well as for evaluating cortical integrity and endosteal scalloping, which are crucial features for evaluating chondroid tumors. While plain X-rays can show obvious calcifications, CT provides much greater detail and eliminates superimposition. MRI is excellent for soft tissue contrast but less sensitive for calcifications.

Question 5296

Topic: 10. Pathology and Oncology

What feature is least suggestive of a benign enchondroma and more concerning for a low-grade chondrosarcoma?

. Smooth, intact periosteum
. Sharp interface with normal marrow
. Absence of soft tissue mass
. Extensive bone destruction and cortical breakthrough
. Lobulated growth pattern

Correct Answer & Explanation

. Extensive bone destruction and cortical breakthrough

Explanation

Extensive bone destruction and cortical breakthrough with an associated soft tissue mass are definitive signs of an aggressive, malignant process, such as a chondrosarcoma. Benign enchondromas typically have an intact, smooth periosteum, a sharp interface with normal marrow, and do not extend into the soft tissues. A lobulated growth pattern is characteristic of cartilaginous tumors, both benign and malignant.

Question 5297

Topic: Bone Tumors

A rare variant of enchondroma that presents as an exophytic lesion mimicking an osteochondroma but composed entirely of cartilage is known as:

. Enchondroma perosteum
. Enchondroma protuberans
. Juxtacortical chondroma
. Chondromyxoid fibroma
. Periosteal chondroma

Correct Answer & Explanation

. Enchondroma protuberans

Explanation

Enchondroma protuberans is a rare variant of enchondroma that grows exophytically from the bone surface, often mimicking an osteochondroma radiographically, but histologically composed of pure cartilaginous tissue without an overlying bony cap. Periosteal chondromas are also surface lesions, but usually arise from the periosteum itself.

Question 5298

Topic: 10. Pathology and Oncology

A core needle biopsy of a suspicious femoral lesion yields tissue consistent with low-grade chondroid neoplasm, but the pathologist notes cellularity that makes definitive differentiation from enchondroma difficult without further sample. The patient is symptomatic with pain. What is the most appropriate next step?

. Observation with repeat biopsy in 6 months
. Wide en bloc resection
. Intralesional curettage
. Open incisional biopsy or excisional biopsy
. Radiation therapy

Correct Answer & Explanation

. Open incisional biopsy or excisional biopsy

Explanation

When a core needle biopsy of a symptomatic and suspicious chondroid lesion is inconclusive or equivocal between enchondroma and low-grade chondrosarcoma, obtaining a larger tissue sample is crucial for definitive diagnosis. This is best achieved via an open incisional biopsy (if planning a subsequent definitive resection) or an excisional biopsy if the lesion is small and amenable to complete removal. This provides the pathologist with sufficient material to grade the lesion accurately and guide appropriate treatment. Observation is inappropriate for a symptomatic, suspicious, and equivocal lesion.

Question 5299

Topic: 10. Pathology and Oncology

Patients with enchondromas carrying IDH1/IDH2 mutations are associated with what prognosis?

. Increased likelihood of developing other primary tumors
. Higher risk of recurrence after curettage
. Increased risk of malignant transformation to chondrosarcoma
. Resistance to chemotherapy
. Better response to radiation therapy

Correct Answer & Explanation

. Increased risk of malignant transformation to chondrosarcoma

Explanation

IDH1/IDH2 mutations are frequently found in enchondromas and are recognized as a driver mutation in the development of chondrosarcomas. Therefore, the presence of these mutations in an enchondroma is associated with an increased risk of malignant transformation to a chondrosarcoma. This genetic alteration is a key area of current research into the pathogenesis of chondroid tumors.

Question 5300

Topic: 10. Pathology and Oncology
Beyond enchondromatosis and hemangiomas, what other associated features might be seen in Maffucci's syndrome?
. Café-au-lait spots
. Lisch nodules
. Ovarian granulosa cell tumors
. Renal cysts
. Medullary thyroid carcinoma

Correct Answer & Explanation

. Ovarian granulosa cell tumors

Explanation

Maffucci's syndrome is associated with a range of other malignancies beyond chondrosarcoma, including ovarian granulosa cell tumors, angiosarcomas, pancreatic adenocarcinoma, and brain gliomas. This broad oncogenic risk highlights the complex nature of the syndrome. Café-au-lait spots and Lisch nodules are associated with Neurofibromatosis. Renal cysts and medullary thyroid carcinoma are not typically associated with Maffucci's.

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