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Bone Tumors MCQs

Practice Set 37 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 721

Topic: Bone Tumors

A 7-year-old child presents with a well-defined, asymptomatic lesion on a radiograph of the distal femur. The lesion is cortical-based, eccentrically located, and appears lucent with a sclerotic rim. Which term is most accurately used to describe a small, purely cortical lesion with these features?

. Unicameral Bone Cyst
. Aneurysmal Bone Cyst
. Fibrous Cortical Defect
. Osteoid Osteoma
. Chondromyxoid Fibroma

Correct Answer & Explanation

. Fibrous Cortical Defect

Explanation

A small, purely cortical, asymptomatic non-ossifying fibroma is often referred to as a fibrous cortical defect (FCD). FCDs are essentially smaller versions of NOFs, sharing the same histological and radiographic characteristics. They are very common, found in up to 30-40% of children. Unicameral bone cysts and aneurysmal bone cysts are typically medullary. Osteoid osteoma has a characteristic nidus, and chondromyxoid fibroma is a distinct cartilaginous tumor.

Question 722

Topic: Bone Tumors

A 13-year-old boy presents with localized pain in his distal tibia. Radiographs reveal a 5 cm lytic lesion with an irregular sclerotic rim involving more than 50% of the cortex. Given the risk of pathological fracture, which is the most critical factor guiding surgical intervention in this case?

. Patient's preference for early return to sports.
. The exact location (e.g., weight-bearing area).
. The presence of a visible fluid-fluid level on MRI.
. Elevated serum calcium levels.
. The duration of symptoms.

Correct Answer & Explanation

. The exact location (e.g., weight-bearing area).

Explanation

The size and location of the NOF, particularly its involvement of the cortical bone (typically >50% of the diameter or a lesion >2 cm in diameter in a weight-bearing bone), are the most critical factors determining the risk of pathological fracture and, consequently, the need for surgical intervention. While patient preference is considered, it's not the primary 'critical factor' guiding the surgical decision from a medical standpoint. Fluid-fluid levels suggest an ABC, not an NOF. Elevated calcium is irrelevant. Duration of symptoms may indicate progression but not directly fracture risk as much as size/location.

Question 723

Topic: Bone Tumors

On T1-weighted MRI, a Non-Ossifying Fibroma typically demonstrates what signal intensity?

. Markedly hyperintense, similar to fat.
. Hypointense to isointense compared to muscle.
. Heterogeneously hyperintense due to fluid levels.
. Isointense to cortical bone.
. Markedly hypointense due to calcification.

Correct Answer & Explanation

. Hypointense to isointense compared to muscle.

Explanation

NOFs are predominantly fibrous lesions. On T1-weighted MRI, they typically appear hypointense to isointense relative to muscle. Any areas of lipid-laden foam cells might slightly increase signal, but the overall fibrous content makes it less bright than fat and without the heterogeneous fluid signals of an ABC. It is not markedly calcified like an osteochondroma, nor is it isointense to cortical bone which is dark on all sequences.

Question 724

Topic: Bone Tumors

On T2-weighted MRI, a Non-Ossifying Fibroma typically demonstrates what signal intensity?

. Markedly hypointense due to dense collagen.
. Markedly hyperintense due to high fluid content.
. Variable signal intensity, often intermediate to hyperintense, depending on fibrous and fluid content.
. Signal void due to high iron deposition.
. Bright with internal fluid-fluid levels.

Correct Answer & Explanation

. Variable signal intensity, often intermediate to hyperintense, depending on fibrous and fluid content.

Explanation

On T2-weighted MRI, the signal intensity of a NOF can be variable. Areas of dense fibrous tissue appear hypointense, while areas with more cellularity, edema, or myxoid changes can appear intermediate to hyperintense. It is not typically 'markedly hypointense' (which would imply very dense, inactive tissue) nor 'markedly hyperintense' (which would imply significant fluid or vascularity like an ABC). Fluid-fluid levels are characteristic of ABCs, not NOFs. Signal void from iron deposition is not a primary feature.

Question 725

Topic: Bone Tumors

Which of the following microscopic features is LEAST characteristic of a Non-Ossifying Fibroma?

. Spindle cell proliferation in a storiform pattern.
. Scattered multinucleated giant cells.
. Presence of foam cells (lipid-laden macrophages).
. Production of osteoid and woven bone trabeculae.
. Hemosiderin deposition.

Correct Answer & Explanation

. Production of osteoid and woven bone trabeculae.

Explanation

While NOFs are fibrous lesions, they do not typically produce osteoid or woven bone trabeculae, which would be characteristic of osteoid osteoma, osteoblastoma, or fibrous dysplasia. The other features (storiform spindle cells, giant cells, foam cells, hemosiderin) are classic histological hallmarks of NOF.

Question 726

Topic: Bone Tumors

The 'active' phase of a Non-Ossifying Fibroma on radiographs is characterized by:

. A completely sclerotic lesion with dense ossification.
. A well-defined, lucent lesion with a sclerotic rim and cortical thinning.
. A diffuse, permeative lesion with indistinct margins.
. Multiple fluid-fluid levels within the lesion.
. A central nidus surrounded by a sclerotic halo.

Correct Answer & Explanation

. A well-defined, lucent lesion with a sclerotic rim and cortical thinning.

Explanation

The 'active' phase of an NOF (or fibrous cortical defect) is characterized by a lucent, often eccentric, well-defined lesion with a sclerotic rim and cortical thinning. This phase represents the growing or mature fibrous lesion. The 'latent' or healing phase shows increasing sclerosis and eventual complete fill-in. Diffuse permeative lesions are aggressive. Fluid-fluid levels are ABCs. A central nidus is an osteoid osteoma.

Question 727

Topic: Bone Tumors

A 10-year-old with a known NOF in the distal tibia is scheduled for a follow-up radiograph in 6 months. What radiographic finding would indicate the lesion is entering its 'healing' or 'latent' phase?

. Increased size and further cortical thinning.
. Development of new periosteal reaction.
. Increased central sclerosis and gradual filling in of the lucency.
. Development of fluid-fluid levels.
. Soft tissue mass formation adjacent to the lesion.

Correct Answer & Explanation

. Increased central sclerosis and gradual filling in of the lucency.

Explanation

The 'healing' or 'latent' phase of a Non-Ossifying Fibroma is characterized by a gradual increase in central sclerosis, with the lesion becoming denser and eventually filling in with normal bone. The lesion typically shrinks and the lucent area is replaced by opaque bone. Increased size, periosteal reaction, fluid-fluid levels, or soft tissue masses are signs of lesion activity, other pathologies, or complications, not healing NOF.

Question 728

Topic: Bone Tumors

A 9-year-old patient presents with chronic, dull pain in the knee, worse at night and relieved by NSAIDs. Radiographs show a small (1.5 cm) lucent lesion with a central nidus and surrounding sclerotic bone in the proximal tibia. While considering the differential, why is a NOF less likely than Osteoid Osteoma in this specific clinical presentation?

. NOFs are typically purely lytic, lacking a central nidus.
. NOFs are never painful.
. NOFs are typically larger than 1.5 cm.
. Pain from NOF is not relieved by NSAIDs.
. NOFs commonly cause night pain.

Correct Answer & Explanation

. NOFs are typically purely lytic, lacking a central nidus.

Explanation

The classic presentation of an Osteoid Osteoma includes chronic pain, often worse at night, and characteristic relief with NSAIDs, along with a small lucent nidus and reactive sclerosis. While NOFs can cause pain, especially if large or fractured, they rarely present with night pain specifically relieved by NSAIDs, and their radiographic appearance is a purely lytic lesion with a sclerotic rim, not a distinct central nidus. NOFs can be small (fibrous cortical defect) or large.

Question 729

Topic: Bone Tumors

Which radiological sign, if present, would strongly suggest a diagnosis other than Non-Ossifying Fibroma in a metaphyseal lesion?

. Eccentric cortical location.
. Sclerotic rim.
. Fluid-fluid levels on MRI.
. Multiloculated appearance.
. Cortical thinning.

Correct Answer & Explanation

. Fluid-fluid levels on MRI.

Explanation

Fluid-fluid levels on MRI are highly characteristic of an Aneurysmal Bone Cyst (ABC) and are typically not seen in a Non-Ossifying Fibroma. While NOFs can be eccentric, have a sclerotic rim, appear multiloculated, and cause cortical thinning, the presence of fluid-fluid levels would strongly point away from an NOF and towards an ABC or other cystic/hemorrhagic lesion.

Question 730

Topic: Bone Tumors

Which imaging finding is characteristic of a healing or 'burnt-out' Non-Ossifying Fibroma?

. Persistent large lytic lesion with no change.
. Increasingly dense, homogenous sclerosis filling the defect.
. Development of new fluid-fluid levels.
. Cortical erosion and periosteal reaction.
. Expansion into the joint space.

Correct Answer & Explanation

. Increasingly dense, homogenous sclerosis filling the defect.

Explanation

A healing or 'burnt-out' NOF is characterized by increasing central sclerosis as the fibrous tissue is replaced by normal bone, eventually leaving a dense, homogenous sclerotic area. The lesion effectively resolves and fills in. Persistent lucency, new fluid levels, cortical erosion with periosteal reaction, or joint space invasion are not typical for a healing NOF.

Question 731

Topic: Bone Tumors
A 10-year-old is incidentally found to have a small, <1 cm, purely cortical fibrous lesion in the distal femur. What is the most appropriate descriptive term for this lesion?
. Non-Ossifying Fibroma
. Fibrous Cortical Defect
. Osteofibrous Dysplasia
. Unicameral Bone Cyst
. Cortical Desmoid

Correct Answer & Explanation

. Fibrous Cortical Defect

Explanation

A small (<2-3 cm), purely cortical fibrous lesion in the metaphysis is most accurately termed a Fibrous Cortical Defect (FCD). Non-Ossifying Fibroma (NOF) is typically used for larger lesions that extend into the medullary cavity, though they are considered the same entity pathologically. Osteofibrous dysplasia is a distinct entity often in the tibia/fibula with epithelial rests. UBC is medullary and cystic. Cortical desmoid is a normal variant (stress phenomenon) at the posterior medial femoral condyle, often bilateral.

Question 732

Topic: Bone Tumors

What is the typical imaging appearance of an osteoid osteoma in the spine on CT?

. Purely lytic lesion with soft tissue mass
. Expansile 'soap bubble' appearance
. Central lucent nidus surrounded by dense reactive sclerosis
. Homogeneous blastic lesion
. T1 hyperintense, T2 hyperintense lesion

Correct Answer & Explanation

. Central lucent nidus surrounded by dense reactive sclerosis

Explanation

Osteoid osteomas are benign bone-forming tumors characterized by a small, radiolucent nidus (typically < 1.5 cm) surrounded by a zone of dense reactive sclerosis. This appearance is best seen on CT. The nidus is the metabolically active part and often shows intense uptake on bone scan. The other options describe different types of lesions: Ewing's/metastasis (lytic with soft tissue), aneurysmal bone cyst ('soap bubble'), blastic metastasis (homogeneous blastic), and hemangioma (T1/T2 hyperintense).

Question 733

Topic: Bone Tumors

Which of the following features on MRI is most characteristic of a myxopapillary ependymoma of the filum terminale?

. Large associated syrinx within the spinal cord
. Expansile lesion with multiple fluid-fluid levels
. Well-circumscribed, lobulated, enhancing lesion at the conus/filum terminale, often with peripheral hemosiderin capping due to hemorrhage
. Intradural-extramedullary location with a dural tail sign
. Intramedullary lesion with heterogeneous enhancement and associated peritumoral edema

Correct Answer & Explanation

. Well-circumscribed, lobulated, enhancing lesion at the conus/filum terminale, often with peripheral hemosiderin capping due to hemorrhage

Explanation

Myxopapillary ependymomas are typically found at the conus medullaris or filum terminale. On MRI, they are characteristically well-circumscribed, lobulated, and show strong homogeneous enhancement. A key feature is the presence of peripheral hemosiderin capping or intratumoral hemorrhage, often seen as T1/T2 signal changes due to blood products, resulting from their high vascularity and tendency to bleed. A large syrinx is more typical of higher cervical/thoracic ependymomas. Fluid-fluid levels are characteristic of ABC. Dural tail is for meningioma. Heterogeneous enhancement with peritumoral edema is less specific.

Question 734

Topic: Bone Tumors

When evaluating a shoulder X-ray, how can an osteophyte be radiographically differentiated from an osteochondroma?

. Osteophytes are always larger
. Osteochondromas show continuity of cortex and medulla with the underlying bone
. Osteophytes cause joint space narrowing
. Osteochondromas are exclusively found at joint margins
. Osteophytes are always pedunculated

Correct Answer & Explanation

. Osteochondromas show continuity of cortex and medulla with the underlying bone

Explanation

The key radiographic feature differentiating an osteochondroma from an osteophyte (or other bone lesion) is the continuity of its cortical and medullary bone with the underlying parent bone. Osteophytes are bony outgrowths at joint margins, associated with degenerative changes, and do not necessarily show this medullary continuity. Osteochondromas can be sessile or pedunculated and originate from the bone surface, often near growth plates, not exclusively at joint margins.

Question 735

Topic: Bone Tumors

A 19-year-old male presents with night pain in his tibia that is dramatically relieved by NSAIDs. Radiographs show a small radiolucent nidus surrounded by dense sclerotic bone. The dramatic pain relief provided by NSAIDs is due to the inhibition of which molecule highly produced by this lesion?

. Interleukin-1 (IL-1)
. Tumor necrosis factor-alpha (TNF-a)
. Prostaglandin E2 (PGE2)
. Transforming growth factor-beta (TGF-b)
. Bone morphogenetic protein-2 (BMP-2)

Correct Answer & Explanation

. Prostaglandin E2 (PGE2)

Explanation

The typical presentation describes an osteoid osteoma. The nidus of an osteoid osteoma produces high levels of Prostaglandin E2 (PGE2), which causes the severe, localized night pain that is characteristically relieved by NSAIDs.

Question 736

Topic: Bone Tumors

A 9-year-old boy presents with arm pain after throwing a baseball. Radiographs reveal a minimally displaced pathologic fracture through a centrally located, geographic, purely radiolucent lesion in the proximal humerus metaphysis. A small fragment of cortical bone is seen resting at the dependent portion of the radiolucent cavity.

What is the most likely diagnosis?

. Aneurysmal bone cyst
. Unicameral bone cyst
. Non-ossifying fibroma
. Eosinophilic granuloma
. Osteosarcoma

Correct Answer & Explanation

. Unicameral bone cyst

Explanation

The scenario describes the classic 'fallen leaf' (or 'fallen fragment') sign, which is pathognomonic for a unicameral bone cyst (UBC), also known as a simple bone cyst. It occurs when a piece of the thin cortical wall fractures and falls into the fluid-filled cavity. Aneurysmal bone cysts (ABCs) are typically eccentrically located and expansile, and do not demonstrate this sign.

Question 737

Topic: Bone Tumors
A 55-year-old male presents with deep thigh pain. Radiographs show a large destructive diaphyseal lesion with 'popcorn' calcification. Histology shows abundant hyaline cartilage with significant atypia. Which of the following is the mainstay of treatment for conventional Grade II chondrosarcoma?
. Neoadjuvant chemotherapy followed by wide surgical resection
. Definitive radiation therapy
. Wide surgical resection alone
. Curettage and cementation
. Primary amputation

Correct Answer & Explanation

. Wide surgical resection alone

Explanation

Conventional chondrosarcomas are notoriously resistant to both chemotherapy and radiation therapy due to their poor vascularity, extracellular matrix, and slow growth rate. The mainstay of treatment for intermediate to high-grade (Grade II or III) chondrosarcomas is wide surgical resection alone.

Question 738

Topic: Bone Tumors

A 65-year-old male presents with persistent mid-back pain, fatigue, and recent onset of polyuria. Laboratory tests reveal normocytic anemia and hypercalcemia. Radiographs show multiple punched-out lytic lesions in the vertebral bodies. Which of the following is the most appropriate initial diagnostic test to confirm the underlying pathology?

. Bone scintigraphy (Tc-99m)
. Serum alkaline phosphatase
. Serum and urine protein electrophoresis
. Dual-energy X-ray absorptiometry (DEXA)
. Positron emission tomography (PET)

Correct Answer & Explanation

. Serum and urine protein electrophoresis

Explanation

Serum and urine protein electrophoresis with immunofixation is the most appropriate initial diagnostic test for multiple myeloma. It detects the monoclonal protein spike (M-spike) characteristic of the disease. Bone scans are notoriously falsely negative in multiple myeloma as the lesions are purely lytic with little reactive bone formation.

Question 739

Topic: Bone Tumors

A 14-year-old boy presents with progressive knee pain. Radiographs reveal an eccentric, expansile, lytic lesion in the distal femoral metaphysis. MRI demonstrates multiple fluid-fluid levels within the lesion. What is the most likely diagnosis?

. Aneurysmal bone cyst
. Unicameral bone cyst
. Osteosarcoma
. Chondroblastoma
. Non-ossifying fibroma

Correct Answer & Explanation

. Aneurysmal bone cyst

Explanation

An aneurysmal bone cyst (ABC) typically presents as a benign, eccentric, blood-filled lytic lesion in the metaphysis of growing children. Fluid-fluid levels on MRI, representing layering of blood products, are a classic hallmark.

Question 740

Topic: Bone Tumors

A 65-year-old male presents with a pathologic fracture of the proximal humerus. Laboratory workup reveals hypercalcemia, anemia, and elevated total serum protein. Radiographs show multiple 'punched-out' lytic lesions in the skull and pelvis. Which of the following tests is most definitive for confirming the underlying diagnosis?

. Serum alkaline phosphatase levels
. Prostate-specific antigen (PSA)
. Serum and urine protein electrophoresis (SPEP/UPEP)
. Bone scan (technetium-99m)
. Erythrocyte sedimentation rate (ESR)

Correct Answer & Explanation

. Serum and urine protein electrophoresis (SPEP/UPEP)

Explanation

The clinical presentation (pathologic fracture, hypercalcemia, anemia, punched-out lytic lesions) is classic for Multiple Myeloma. The most definitive initial non-invasive diagnostic tests are serum and urine protein electrophoresis (SPEP and UPEP) with immunofixation to detect a monoclonal (M) protein spike. Bone scans are often falsely negative in multiple myeloma because the lesions are purely lytic.

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