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Bone Tumors MCQs

Practice Set 36 of 52

This practice set contains high-yield board review questions covering key concepts in Bone Tumors. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 701

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 702

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 703

Topic: Bone Tumors

What is the typical age range for presentation of conventional central chondrosarcoma?

. 0-10 years
. 10-20 years
. 20-30 years
. 30-60 years
. 70+ years

Correct Answer & Explanation

. 30-60 years

Explanation

Conventional central chondrosarcoma typically presents in adults, most commonly in the 3rd to 6th decades of life (30-60 years). It is rare in children and adolescents. While it can occur in older individuals, the peak incidence is within this range. Other variants like mesenchymal chondrosarcoma can occur in younger individuals.

Question 704

Topic: Bone Tumors

What is the primary reason for the resistance of conventional chondrosarcoma to conventional chemotherapy and external beam radiation therapy?

. Rapid proliferation rate of chondrocytes
. Lack of specific growth factor receptors
. Poor vascularity and hypoxic environment of cartilage
. High expression of multi-drug resistance proteins
. Inability of drugs to penetrate the cartilaginous matrix

Correct Answer & Explanation

. Poor vascularity and hypoxic environment of cartilage

Explanation

The primary reason for chondrosarcoma's resistance to chemotherapy and radiation therapy is attributed to the inherent poor vascularity and hypoxic environment of cartilaginous tissue, which limits drug delivery and the effectiveness of radiation. Chondrosarcomas generally have a slow growth rate, and while multi-drug resistance proteins can play a role, the fundamental nature of cartilage is key.

Question 705

Topic: Bone Tumors

Which of the following is typically a feature of Grade 1 conventional chondrosarcoma on histopathology?

. Prominent spindle cell component
. High cellularity with significant nuclear atypia and numerous mitotic figures
. Bland chondrocytes with small, uniform nuclei and rare mitotic figures, often with increased cellularity compared to enchondroma
. Areas of osteoid or bone formation within the cartilaginous matrix
. Large areas of necrosis

Correct Answer & Explanation

. Bland chondrocytes with small, uniform nuclei and rare mitotic figures, often with increased cellularity compared to enchondroma

Explanation

Grade 1 conventional chondrosarcoma is characterized by bland chondrocytes with small, uniform nuclei, often increased cellularity compared to an enchondroma, and rare or absent mitotic figures. It can be challenging to distinguish from enchondroma. Prominent spindle cells, high cellularity with significant atypia and mitoses, and necrosis are features of higher-grade chondrosarcomas or other sarcomas. Osteoid/bone formation would suggest osteosarcoma or dedifferentiated chondrosarcoma if it were an anaplastic component.

Question 706

Topic: Bone Tumors

Which of the following is most commonly associated with the highest rate of local recurrence after intralesional treatment?

. Grade 1 conventional chondrosarcoma of the phalanx
. Grade 2 conventional chondrosarcoma of the proximal humerus
. Clear cell chondrosarcoma of the proximal tibia
. Mesenchymal chondrosarcoma of the sacrum
. Grade 3 conventional chondrosarcoma of the ilium

Correct Answer & Explanation

. Grade 3 conventional chondrosarcoma of the ilium

Explanation

Intralesional treatment is generally contraindicated for any chondrosarcoma due to high recurrence rates, but its application to Grade 3 conventional chondrosarcoma of the ilium would yield the highest local recurrence rate due to the tumor's aggressive nature, high-grade histology, and the inherent difficulty of achieving true intralesional margins in the pelvis without contamination. Even Grade 2 lesions treated intralesionally would have high recurrence, but Grade 3 is worse. Phalanx lesions are often low-grade and more amenable to marginal excision. Mesenchymal chondrosarcoma and clear cell chondrosarcoma are distinct entities with their own characteristics.

Question 707

Topic: Bone Tumors

Which of the following features on a plain radiograph is most concerning for a low-grade central chondrosarcoma over an enchondroma?

. Expansile remodeling of the bone
. Presence of an intact sclerotic rim
. Punctate or ring-and-arc calcifications
. Diffuse cortical thickening and endosteal scalloping >2/3 of cortical thickness
. Well-defined lucent lesion in the diaphysis

Correct Answer & Explanation

. Diffuse cortical thickening and endosteal scalloping >2/3 of cortical thickness

Explanation

Diffuse cortical thickening and endosteal scalloping greater than 2/3 of the cortical thickness are strong indicators of a low-grade chondrosarcoma, signifying an infiltrative and slowly aggressive growth pattern. While expansile remodeling and calcifications can be seen in both, and an intact sclerotic rim usually favors benignity, significant cortical erosion/scalloping points towards malignancy. A well-defined lucent lesion is non-specific.

Question 708

Topic: Bone Tumors

What is the most common subtype of chondrosarcoma?

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

Correct Answer & Explanation

. Conventional central chondrosarcoma

Explanation

Conventional central chondrosarcoma accounts for the vast majority (approximately 85-90%) of all chondrosarcomas. The other subtypes listed are rare variants.

Question 709

Topic: Bone Tumors

Which of the following scenarios would most likely warrant consideration of neoadjuvant therapy (chemotherapy or radiation) for a chondrosarcoma, despite its general resistance?

. Grade 1 conventional chondrosarcoma in the proximal femur
. Small, resectable clear cell chondrosarcoma
. Mesenchymal chondrosarcoma in the spine causing neurological deficit
. Secondary peripheral chondrosarcoma of the scapula
. Low-grade central chondrosarcoma of the phalanx

Correct Answer & Explanation

. Mesenchymal chondrosarcoma in the spine causing neurological deficit

Explanation

While conventional chondrosarcomas are largely resistant, mesenchymal chondrosarcoma is an exception, showing some chemosensitivity. For a mesenchymal chondrosarcoma, especially in a difficult anatomical location like the spine causing neurological deficits, neoadjuvant chemotherapy may be considered to attempt tumor shrinkage and facilitate a safer, more complete resection. For other types of chondrosarcoma, neoadjuvant therapy is generally ineffective and not indicated as primary treatment. Grade 1 or clear cell types are generally managed surgically without neoadjuvant therapy. Peripheral chondrosarcoma is also primarily surgical.

Question 710

Topic: Bone Tumors

Which chondrosarcoma variant has a predilection for the craniofacial bones, particularly the maxilla and mandible, and exhibits a high local recurrence rate?

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

Correct Answer & Explanation

. Mesenchymal chondrosarcoma

Explanation

Mesenchymal chondrosarcoma has a distinct predilection for axial sites, including the craniofacial bones (especially maxilla, mandible, skull base), spine, and ribs. It is known for its aggressive nature, high local recurrence rate, and metastatic potential. The other types are less common in these specific locations or have different characteristic patterns.

Question 711

Topic: Bone Tumors

Which type of chondrosarcoma is least likely to respond to systemic chemotherapy?

. Mesenchymal chondrosarcoma
. Dedifferentiated chondrosarcoma (high-grade component)
. Conventional central chondrosarcoma Grade 1
. Conventional central chondrosarcoma Grade 3
. Clear cell chondrosarcoma

Correct Answer & Explanation

. Conventional central chondrosarcoma Grade 1

Explanation

Conventional central chondrosarcoma, particularly Grade 1, is notoriously resistant to systemic chemotherapy. Chemotherapy is generally not indicated for low-grade conventional chondrosarcomas. Mesenchymal chondrosarcoma and the high-grade component of dedifferentiated chondrosarcoma may show some limited response to chemotherapy, but conventional chondrosarcoma overall has poor chemosensitivity, and this is especially true for Grade 1. Clear cell is also largely chemorefractory.

Question 712

Topic: Bone Tumors

Which statement regarding dedifferentiated chondrosarcoma is correct?

. It represents a progression from Grade 1 to Grade 3 conventional chondrosarcoma.
. It typically arises de novo without a pre-existing cartilaginous lesion.
. It is characterized by a biphasic morphology of low-grade chondrosarcoma and high-grade non-cartilaginous sarcoma.
. It has a better prognosis than conventional Grade 3 chondrosarcoma.
. It is treated effectively with intralesional curettage and radiation.

Correct Answer & Explanation

. It is characterized by a biphasic morphology of low-grade chondrosarcoma and high-grade non-cartilaginous sarcoma.

Explanation

Dedifferentiated chondrosarcoma is pathologically defined by its biphasic morphology, consisting of a low-grade conventional chondrosarcoma component sharply juxtaposed with a high-grade, non-cartilaginous sarcoma (e.g., osteosarcoma, fibrosarcoma). It has a very poor prognosis, worse than conventional Grade 3 chondrosarcoma. It does not simply represent a grade progression but a distinct, more aggressive entity. It often arises from a pre-existing cartilaginous lesion or conventional chondrosarcoma. Intralesional curettage and radiation are ineffective.

Question 713

Topic: Bone Tumors

A 62-year-old patient undergoes an unplanned intralesional excision for what was thought to be an enchondroma of the proximal femur. Final pathology reveals a Grade 2 chondrosarcoma with positive margins. What is the most appropriate next step?

. Observation with serial imaging
. Adjuvant radiation therapy alone
. Systemic chemotherapy
. Re-excision with wide margins
. Palliative care

Correct Answer & Explanation

. Re-excision with wide margins

Explanation

An unplanned intralesional excision of a Grade 2 chondrosarcoma with positive margins necessitates a planned re-excision with wide margins. This is crucial for local control and to prevent recurrence and potential dedifferentiation. Observation is inadequate. Adjuvant radiation is generally ineffective for conventional chondrosarcoma. Chemotherapy is not a primary treatment for conventional chondrosarcoma. Palliative care is not appropriate given the potential for cure with adequate surgery.

Question 714

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 715

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 716

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 717

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 718

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 719

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 720

Topic: Bone Tumors

A 9-year-old girl has routine X-rays following a minor ankle sprain, revealing an incidental, well-defined, lytic lesion with a sclerotic rim in the distal tibial metaphysis. The lesion appears eccentric and mildly expansile. Which MRI sequence would be most helpful in distinguishing a NOF from an aneurysmal bone cyst (ABC) or unicameral bone cyst (UBC)?

. T1-weighted sequence
. T2-weighted sequence
. Fat-suppressed T2-weighted sequence
. Post-contrast T1-weighted sequence
. Gradient Echo sequence

Correct Answer & Explanation

. Post-contrast T1-weighted sequence

Explanation

While T1 and T2 sequences provide information on signal characteristics (NOFs typically show low to intermediate T1 and variable T2 signal depending on fibrous content and lipid), a post-contrast T1-weighted sequence is crucial for differentiating cystic lesions. Aneurysmal bone cysts (ABCs) characteristically show internal septal enhancement with fluid-fluid levels, while unicameral bone cysts (UBCs) typically show minimal to no internal enhancement, often just peripheral rim enhancement. NOFs will often show solid or peripheral enhancement of the fibrous tissue, distinguishing them from cystic lesions with fluid-fluid levels or simple fluid.

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