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Bone Tumors MCQs

Practice Set 28 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 541

Topic: Bone Tumors

Which of the following describes the characteristic radiographic appearance of a unicameral bone cyst (UBC)?

. Sunburst periosteal reaction with Codman's triangle
. Ground-glass appearance with shepherd's crook deformity
. Eccentric lytic lesion with cortical destruction
. Metaphyseal lesion with 'fallen leaf' sign
. Onion-skin periosteal reaction

Correct Answer & Explanation

. Metaphyseal lesion with 'fallen leaf' sign

Explanation

A unicameral bone cyst (UBC), or simple bone cyst, is typically a metaphyseal lesion (often proximal humerus or femur) that appears as a well-circumscribed, lytic lesion. The 'fallen leaf' sign refers to a fragment of cortical bone that has fractured off and fallen into the fluid-filled cavity of the cyst, indicating a pathologic fracture through the cyst. Sunburst reaction and Codman's triangle are associated with osteosarcoma. Ground-glass appearance with shepherd's crook deformity is characteristic of fibrous dysplasia. Eccentric lytic lesion with cortical destruction is more indicative of aggressive tumors like osteosarcoma or giant cell tumor. Onion-skin reaction is seen in Ewing sarcoma.

Question 542

Topic: Bone Tumors

Which of the following describes the characteristic radiographic appearance of fibrous dysplasia?

. Sunburst periosteal reaction with Codman's triangle
. Ground-glass appearance with shepherd's crook deformity
. Onion-skin periosteal reaction
. Lytic lesion with a 'soap bubble' appearance
. Dense sclerosis with a central nidus

Correct Answer & Explanation

. Ground-glass appearance with shepherd's crook deformity

Explanation

Fibrous dysplasia is characterized by a 'ground-glass' appearance on radiographs due to immature woven bone within a fibrous stroma. When affecting the proximal femur, severe forms can lead to bowing and deformity known as a 'shepherd's crook deformity.' Sunburst reaction is osteosarcoma. Onion-skin reaction is Ewing sarcoma. Lytic lesions with 'soap bubble' appearance can be seen in aneurysmal bone cysts or giant cell tumors. Dense sclerosis with a central nidus is characteristic of osteoid osteoma.

Question 543

Topic: Bone Tumors

What is the classic radiographic finding associated with osteosarcoma?

. Punctuated calcifications with a 'ring and arc' pattern
. Expansile lytic lesion with a 'soap bubble' appearance
. Cortical thickening and periosteal reaction with 'onion skin' appearance
. Sunburst periosteal reaction and Codman's triangle
. Geographic lysis with sclerotic border

Correct Answer & Explanation

. Sunburst periosteal reaction and Codman's triangle

Explanation

Osteosarcoma classically presents with aggressive radiographic features, including a 'sunburst' periosteal reaction (spicules of new bone radiating outwards) and Codman's triangle (triangular elevation of the periosteum at the margins of the lesion). These indicate rapid bone formation and destruction. 'Ring and arc' calcifications are characteristic of chondrosarcoma. 'Soap bubble' appearance is often seen in giant cell tumors. 'Onion skin' periosteal reaction is characteristic of Ewing's sarcoma. Geographic lysis with a sclerotic border is more indicative of a benign or slow-growing lesion.

Question 544

Topic: Bone Tumors

A 14-year-old boy presents with progressive knee pain and swelling over the past 2 months. A representative imaging study of the distal femur is shown below.

Assuming the radiograph demonstrates a destructive metaphyseal lesion with a 'sunburst' periosteal reaction and Codman's triangle, what is the most likely diagnosis?

. Osteosarcoma
. Ewing Sarcoma
. Giant Cell Tumor
. Chondrosarcoma
. Osteoid Osteoma

Correct Answer & Explanation

. Osteosarcoma

Explanation

The clinical presentation of a teenager with a destructive, bone-forming metaphyseal lesion demonstrating aggressive periosteal reactions (like a sunburst pattern or Codman's triangle) is highly characteristic of conventional osteosarcoma. Giant cell tumors are typically epiphyseal, and Ewing sarcoma usually presents as a permeative diaphyseal lesion with 'onion-skin' periosteal reaction.

Question 545

Topic: Bone Tumors

A 30-year-old patient undergoes surgical resection of a low-grade chondrosarcoma from the proximal humerus. The surgeon achieves an intralesional margin due to anatomical constraints (proximity to glenoid and neurovascular structures) but meticulously burrs the cavity and uses adjuvant cryotherapy. What is the most significant risk associated with this approach for a chondrosarcoma?

. Increased risk of pathological fracture
. High rate of distant metastasis
. Significant increase in local recurrence
. Development of post-operative infection
. Compromised shoulder function

Correct Answer & Explanation

. Significant increase in local recurrence

Explanation

Chondrosarcomas, even low-grade ones, are known for their potential for local recurrence, especially after intralesional or marginal resections. Chondrosarcoma cells can be left behind within the pseudo-capsule or surrounding tissues with intralesional approaches. While adjuvant treatments like burring and cryotherapy aim to reduce this risk, an intralesional margin inherently carries a significantly higher risk of local recurrence compared to marginal or wide excisions. Pathological fracture, distant metastasis (for low-grade, this risk is low), infection, and functional compromise are potential complications of any surgery but not themost significantrisk specific to an intralesional approach for chondrosarcoma. Local recurrence is the primary concern for oncologic outcome.

Question 546

Topic: Bone Tumors

Which benign bone tumor is most commonly found in the metaphysis of long bones, particularly the distal femur or proximal tibia, and has a characteristic 'ground glass' or 'fibrous' appearance on X-ray, often with an intact cortex?

. Osteochondroma
. Non-ossifying fibroma (NOF)
. Fibrous dysplasia
. Enchondroma
. Osteoblastoma

Correct Answer & Explanation

. Fibrous dysplasia

Explanation

Fibrous dysplasia is a developmental anomaly of bone characterized by the replacement of normal bone marrow and cancellous bone with fibrous tissue and immature woven bone. It classically presents in the metaphysis/diaphysis of long bones (e.g., femur, tibia), has a 'ground glass' or 'shepherd's crook' deformity appearance on X-ray, often with an intact or expanded cortex. Non-ossifying fibroma is also metaphyseal but has a more 'bubbly' or 'soap-bubble' appearance. Osteochondroma is an exostosis. Enchondroma is a cartilaginous lesion, often in small bones of hands/feet. Osteoblastoma is similar to osteoid osteoma but larger.

Question 547

Topic: Bone Tumors

Which of the following primary bone tumors is most commonly associated with a 'sunburst' or 'Codman's triangle' appearance on plain radiographs?

. Chondrosarcoma
. Ewing sarcoma
. Osteosarcoma
. Multiple myeloma
. Enchondroma

Correct Answer & Explanation

. Osteosarcoma

Explanation

Osteosarcoma, particularly the conventional intramedullary type, is classically associated with aggressive periosteal reactions. These include a 'sunburst' pattern (spicules of bone radiating outwards from the cortex) and 'Codman's triangle' (elevation of the periosteum creating a triangular area). These signs indicate rapid bone formation by the tumor and aggressive periosteal lifting. While Ewing sarcoma can also have an aggressive periosteal reaction ('onion skin'), and chondrosarcoma can have matrix calcification, the 'sunburst' and 'Codman's triangle' are most characteristic of osteosarcoma.

Question 548

Topic: Bone Tumors

A 19-year-old male complains of severe, progressively worsening pain in his left thigh that is notably worse at night. The pain is rapidly relieved by ibuprofen. A CT scan reveals a 0.8 cm radiolucent nidus surrounded by reactive sclerosis in the femoral diaphysis. What is the primary mechanism by which nonsteroidal anti-inflammatory drugs (NSAIDs) relieve this patient's pain?

. Inhibition of leukotriene synthesis within the nidus
. Decreased production of interleukins
. Inhibition of cyclooxygenase, decreasing high levels of Prostaglandin E2
. Direct suppression of osteoclast activity
. Reduction of substance P in the surrounding periosteum

Correct Answer & Explanation

. Inhibition of cyclooxygenase, decreasing high levels of Prostaglandin E2

Explanation

The classic presentation of an osteoid osteoma is night pain exquisitely relieved by NSAIDs. This is due to the high concentration of Prostaglandin E2 (PGE2) produced by the central nidus, which is inhibited by NSAIDs via cyclooxygenase blockade.

Question 549

Topic: Bone Tumors

A 22-year-old man complains of a dull, aching pain in his right tibia that worsens at night and is dramatically relieved by ibuprofen. Radiographs show thickened cortical bone with a small 8mm radiolucent nidus. Which of the following is the most appropriate first-line definitive treatment if conservative management fails?

. Open intralesional curettage and bone grafting
. Wide en bloc resection
. Radiofrequency ablation
. External beam radiation therapy
. Chemotherapy followed by surgical resection

Correct Answer & Explanation

. Radiofrequency ablation

Explanation

The clinical picture is pathognomonic for an osteoid osteoma (night pain relieved by NSAIDs, <1.5 cm radiolucent nidus with surrounding sclerosis). If symptomatic relief with NSAIDs is insufficient or undesired long-term, the gold standard definitive and minimally invasive treatment is percutaneous CT-guided radiofrequency ablation (RFA).

Question 550

Topic: Bone Tumors

A 65-year-old male presents with severe, atraumatic back pain and hypercalcemia. Radiographs show a 'punched-out' lytic lesion in the L3 vertebral body. Suspecting multiple myeloma, a workup is initiated. Which of the following imaging modalities is the LEAST sensitive for detecting additional skeletal lesions in this patient?

. Whole-body low-dose CT
. Positron emission tomography (PET-CT)
. Whole-body MRI
. Technetium-99m bone scintigraphy
. Skeletal survey radiography

Correct Answer & Explanation

. Technetium-99m bone scintigraphy

Explanation

Technetium-99m (Tc-99m) bone scans rely on osteoblastic activity. Multiple myeloma lesions are almost purely osteolytic and lack reactive osteoblastic bone formation; thus, they classically present as 'cold' or yield false-negative results on a bone scan. Low-dose CT, MRI, and PET are vastly superior imaging modalities for the detection of myeloma lesions.

Question 551

Topic: Bone Tumors

A 10-year-old girl is evaluated for multiple bony prominences around her knees and wrists. Radiographs confirm multiple osteochondromas. Genetic testing reveals a mutation in the EXT1 gene. This mutation directly disrupts the biosynthesis of which of the following macromolecules?

. Hyaluronic acid
. Heparan sulfate
. Chondroitin sulfate
. Keratan sulfate
. Type II collagen

Correct Answer & Explanation

. Heparan sulfate

Explanation

Multiple hereditary exostoses (MHE) is an autosomal dominant condition caused by mutations in the EXT1 or EXT2 genes. These genes encode glycosyltransferases essential for the polymerization and biosynthesis of heparan sulfate. The resulting deficiency in heparan sulfate proteoglycans disrupts normal Indian hedgehog (Ihh) signaling at the growth plate, leading to the formation of osteochondromas.

Question 552

Topic: Bone Tumors
A 9-year-old girl presents with a prominent limp and an apparent leg length discrepancy. Radiographs reveal a ground-glass appearance in the proximal femur with a 'shepherd's crook' deformity. Physical examination shows irregular, large pigmented skin patches with rough borders. What is the underlying molecular pathogenesis of this patient's bone lesions?
. Loss of function mutation in the NF1 gene
. Activating mutation in the GNAS gene causing persistent cAMP production
. Mutation in the FGFR3 gene resulting in constitutively active tyrosine kinase
. Defect in the CBFA1/RUNX2 transcription factor
. Inactivating mutation in the SQSTM1 gene

Correct Answer & Explanation

. Activating mutation in the GNAS gene causing persistent cAMP production

Explanation

The clinical picture describes McCune-Albright syndrome, defined by the triad of polyostotic fibrous dysplasia, 'coast of Maine' café-au-lait spots, and endocrinopathies (like precocious puberty). Fibrous dysplasia is caused by a somatic activating mutation in the GNAS gene, which encodes the alpha subunit of the stimulatory G protein (Gs). This leads to constitutively active adenylate cyclase, resulting in elevated intracellular cAMP and subsequent abnormal osteoblast differentiation.

Question 553

Topic: Bone Tumors

A 55-year-old male undergoes en bloc resection of a clival tumor. Histopathology reveals lobulated architecture containing characteristic physaliferous cells with abundant, bubbly, vacuolated cytoplasm embedded in a myxoid stroma. Which of the following immunohistochemical markers is most highly specific for confirming this diagnosis and distinguishing it from a chondrosarcoma?

. S100 protein
. Cytokeratin
. Brachyury
. CD99
. Epithelial Membrane Antigen (EMA)

Correct Answer & Explanation

. Brachyury

Explanation

The lesion described is a chordoma, characterized histologically by physaliferous (bubbly) cells. Differentiating chordoma from chondrosarcoma can sometimes be challenging, particularly in the skull base and spine. Both can be positive for S100. However, Brachyury (a transcription factor crucial for notochord development) is highly sensitive and specific for chordoma and is negative in chondrosarcomas. Chordomas are also typically positive for epithelial markers (Cytokeratin and EMA), whereas conventional chondrosarcomas are negative, but Brachyury is considered the definitive confirmatory marker.

Question 554

Topic: Bone Tumors

A 22-year-old male presents with chronic mid-back pain. He describes the pain as a dull, constant ache that is not reliably relieved by NSAIDs. A CT scan of the thoracic spine shows a 3.5 cm expansile, radiolucent lesion with scattered matrix calcifications originating in the posterior elements of T10. Histology demonstrates interconnected trabeculae of woven bone lined by prominent, plump osteoblasts within a highly vascularized connective tissue stroma. What is the most likely diagnosis?

. Osteoid osteoma
. Osteoblastoma
. Aneurysmal bone cyst
. Chondroblastoma
. Giant cell tumor

Correct Answer & Explanation

. Osteoblastoma

Explanation

The clinical presentation and histology describe an osteoblastoma. Histologically, osteoblastoma is very similar (often identical) to osteoid osteoma, displaying woven bone trabeculae rimmed by active osteoblasts. However, osteoblastomas are distinguished clinically and radiographically by their larger size (>2 cm), progressive growth, and propensity to cause pain that is typically NOT relieved by NSAIDs or aspirin (unlike the nocturnal pain of osteoid osteoma that responds dramatically to NSAIDs). They most commonly occur in the posterior elements of the spine.

Question 555

Topic: Bone Tumors

A 16-year-old boy presents with severe right thigh pain that awakens him from sleep. The pain is consistently and rapidly relieved by taking ibuprofen. A CT scan demonstrates a well-circumscribed 8 mm radiolucent nidus surrounded by dense sclerotic bone in the proximal femur. The intense, nocturnal pain experienced by this patient is directly mediated by dramatically elevated local production of which of the following?

. Interleukin-1 (IL-1)
. Prostaglandin E2 (PGE2)
. Tumor Necrosis Factor-alpha (TNF-a)
. Substance P
. Bradykinin

Correct Answer & Explanation

. Prostaglandin E2 (PGE2)

Explanation

The classic presentation of an osteoid osteoma includes nocturnal pain that is dramatically responsive to NSAIDs. This response occurs because the nidus of the osteoid osteoma produces high levels of Prostaglandin E2 (PGE2). Cyclooxygenase inhibitors (NSAIDs) block the production of PGE2, providing substantial pain relief.

Question 556

Topic: Bone Tumors

A 14-year-old girl is evaluated for a progressive deformity of her proximal femur. Radiographs show a purely lytic lesion in the metadiaphysis with a classic 'ground-glass' matrix and a 'shepherd's crook' varus deformity.

Which of the following genetic alterations is responsible for the pathogenesis of this condition?

. EXT1 mutation
. USP6 rearrangement
. GNAS activating mutation
. TP53 deletion
. RB1 loss of heterozygosity

Correct Answer & Explanation

. GNAS activating mutation

Explanation

The clinical and radiographic description is classic for Fibrous Dysplasia (ground glass matrix, shepherd's crook deformity). Fibrous dysplasia is caused by a somatic activating missense mutation in the GNAS gene (specifically at the Arg201 codon), which encodes the alpha subunit of the Gs stimulatory protein. This leads to constitutive activation of adenylate cyclase and excessive intracellular cAMP, preventing proper maturation of osteoblasts.

Question 557

Topic: Bone Tumors

A 21-year-old male presents with chronic, dull back pain. Radiographs and CT show a 3.5 cm expansile, radiolucent mass with central ossification involving the posterior elements of the L4 vertebra.

Which of the following features differentiates this diagnosis (Osteoblastoma) from an Osteoid Osteoma?

. Size <1.5 cm and nocturnal pain completely relieved by NSAIDs
. Epiphyseal location and "chicken wire" calcification
. Size >2.0 cm and progressive dull aching pain not completely relieved by NSAIDs
. Permeative diaphyseal destruction with an "onion skin" periosteal reaction
. Purely lytic metaphyseal lesion with a "fallen leaf" sign

Correct Answer & Explanation

. Size >2.0 cm and progressive dull aching pain not completely relieved by NSAIDs

Explanation

Osteoblastoma and osteoid osteoma are histologically very similar (forming woven bone trabeculae lined by prominent osteoblasts). However, osteoblastoma is distinguished clinically and radiographically: it is larger (defined as >2 cm, whereas osteoid osteoma is <1.5-2 cm), often found in the spine (posterior elements), and produces a dull, aching pain that is generally NOT completely relieved by NSAIDs, unlike the classic nocturnal NSAID-responsive pain of an osteoid osteoma.

Question 558

Topic: Bone Tumors

An 18-year-old male presents with severe, progressive back pain that worsens at night and is dramatically relieved by naproxen. He has recently developed a painful scoliosis. CT imaging identifies a 1.0 cm radiolucent nidus surrounded by dense reactive sclerosis in the right posterior elements of the T8 vertebra. Regarding the resultant spinal deformity, which statement is most accurate?

. The lesion is typically located on the concavity of the scoliotic curve.
. The lesion is typically located on the convexity of the scoliotic curve.
. The lesion is typically located at the exact apex of the convexity.
. The curvature varies randomly and shows no consistent relationship to the lesion side.
. The resultant scoliosis is always non-structural and purely compensatory for leg length inequality.

Correct Answer & Explanation

. The lesion is typically located on the concavity of the scoliotic curve.

Explanation

The patient has an osteoid osteoma of the spine. When an osteoid osteoma arises in the spine, it predominantly affects the posterior elements (lamina, pedicle). The severe pain causes asymmetric muscle spasm, leading to a scoliotic deformity. Classically, the resulting curve is rigid, and the tumor nidus is found on the concavity of the curve due to the intense local muscle spasm.

Question 559

Topic: Bone Tumors

A 9-year-old boy sustains a proximal humerus fracture after a minor fall. Radiographs demonstrate a fracture through a large, centrally located, radiolucent lesion in the metaphysis that mildly expands the bone. A small fragment of cortical bone is visible resting at the dependent (bottom) portion of the radiolucent cavity.

What is this characteristic radiographic sign called?

. Sunburst sign
. Fallen leaf sign
. Shepherd's crook deformity
. Corduroy sign
. Blade of grass sign

Correct Answer & Explanation

. Fallen leaf sign

Explanation

The 'fallen leaf' or 'fallen fragment' sign is pathognomonic for a Simple Bone Cyst (Unicameral Bone Cyst). Because the cyst is fluid-filled and lacks a solid matrix, a fractured fragment of cortex can fall freely through the fluid to rest at the dependent portion of the cavity. If the cyst were a solid tumor (like an enchondroma or fibrous dysplasia), the fragment would remain suspended in place.

Question 560

Topic: Bone Tumors

A 65-year-old female presents with progressive back pain and fatigue. Radiographs demonstrate multiple 'punched-out' lytic lesions in her skull and lumbar vertebral bodies without a sclerotic rim. Laboratory analysis reveals hypercalcemia, anemia, and an elevated serum creatinine. The primary neoplastic cells involved in this disease process are derived from which of the following cellular lineages?

. Osteoblasts
. Chondrocytes
. T-lymphocytes
. Macrophages
. B-lymphocytes (Plasma cells)

Correct Answer & Explanation

. B-lymphocytes (Plasma cells)

Explanation

The clinical presentation (CRAB criteria: Calcium elevation, Renal insufficiency, Anemia, Bone lesions) and radiographic findings are classic for Multiple Myeloma, the most common primary malignancy of bone in adults. It is characterized by the neoplastic clonal proliferation of plasma cells, which are terminally differentiated B-lymphocytes.

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