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Bone Tumors MCQs

Practice Set 21 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 401

Topic: Bone Tumors

A 70-year-old female with a long-standing history of polyostotic Paget's disease presents with new-onset, severe, and unrelenting pain in her right thigh. Radiographs demonstrate a new destructive, lytic lesion in previously pagetoid bone. What is the most likely diagnosis?

. Chondrosarcoma
. Multiple myeloma
. Ewing sarcoma
. Secondary osteosarcoma

Correct Answer & Explanation

. Secondary osteosarcoma

Explanation

Secondary osteosarcoma is a rare (approx. 1%) but highly lethal complication of Paget's disease. It typically presents as a rapid increase in localized pain and swelling, with radiographs showing a destructive bone lesion.

Question 402

Topic: Bone Tumors
A 7-year-old girl presents with a limp, precocious puberty, and large, irregular, hyperpigmented skin macules. Radiographs of the right femur show an expansile, radiolucent lesion with a "ground-glass" appearance. Which of the following describes the underlying genetic pathogenesis?
. Germline mutation in FGFR3
. Postzygotic somatic mutation in the GNAS gene
. Autosomal recessive mutation in TCIRG1
. Deletion on chromosome 15q
. Mutation in the NF1 gene

Correct Answer & Explanation

. Postzygotic somatic mutation in the GNAS gene

Explanation

McCune-Albright syndrome consists of polyostotic fibrous dysplasia, precocious puberty, and café-au-lait spots with rough "coast of Maine" borders. It is caused by a postzygotic somatic (mosaic) activating mutation in the GNAS gene.

Question 403

Topic: Bone Tumors

A 19-year-old male complains of right thigh pain that is worse at night and dramatically improves with ibuprofen. A CT scan reveals a 7-mm radiolucent nidus surrounded by dense sclerotic bone in the femoral diaphysis. What is the most appropriate definitive treatment?

. Wide surgical excision
. Intralesional steroid injection
. Radiofrequency ablation
. 6 weeks of intravenous antibiotics
. External beam radiation

Correct Answer & Explanation

. Radiofrequency ablation

Explanation

Osteoid osteoma classically presents with nocturnal pain relieved by NSAIDs due to high prostaglandin production by the nidus. Radiofrequency ablation (RFA) is the current gold standard definitive treatment, offering high success rates with minimal morbidity.

Question 404

Topic: Bone Tumors
A 10-year-old girl is evaluated for a shepherd's crook deformity of her proximal femur. Radiographs show a "ground-glass" appearance of the medullary canal. She also has precocious puberty and large café-au-lait macules with irregular borders. What is the underlying genetic mutation?
. NF1
. COL1A1
. FGFR3
. GNAS1
. RUNX2

Correct Answer & Explanation

. GNAS1

Explanation

McCune-Albright syndrome consists of polyostotic fibrous dysplasia, café-au-lait spots with irregular "coast of Maine" borders, and endocrine abnormalities. It is caused by a somatic activating mutation in the GNAS1 gene, which increases intracellular cAMP.

Question 405

Topic: Bone Tumors
A 65-year-old man presents with persistent back pain and fatigue. Blood tests reveal anemia, hypercalcemia, and an elevated creatinine. A serum protein electrophoresis demonstrates a monoclonal spike. Which imaging modality is most sensitive for detecting early impending pathologic fractures in this patient's long bones?
. Technetium-99m bone scan
. Standard skeletal survey (plain radiographs)
. Whole-body low-dose CT (WBLDCT)
. Positron emission tomography (PET)
. Diagnostic ultrasound

Correct Answer & Explanation

. Whole-body low-dose CT (WBLDCT)

Explanation

Multiple myeloma often results in purely lytic bone lesions that may not be active on a traditional Technetium-99m bone scan due to lack of osteoblastic response. Whole-body low-dose CT or MRI is currently favored over standard skeletal surveys for superior sensitivity in detecting lytic lesions.

Question 406

Topic: Bone Tumors

A 12-year-old girl presents with pain and swelling of her distal femur. MRI reveals an expansile, multiloculated metaphyseal lesion containing multiple fluid-fluid levels. Genetic testing of the biopsy specimen identifies a rearrangement of the USP6 gene. What is the diagnosis?

. Unicameral bone cyst
. Giant cell tumor of bone
. Telangiectatic osteosarcoma
. Aneurysmal bone cyst
. Fibrous dysplasia

Correct Answer & Explanation

. Aneurysmal bone cyst

Explanation

Primary aneurysmal bone cysts (ABCs) are characterized radiographically by fluid-fluid levels on MRI and genetically by translocations involving the USP6 gene on chromosome 17p13.

Question 407

Topic: Bone Tumors
A 9-year-old girl is evaluated for precocious puberty, hyperpigmented cutaneous macules with irregular borders, and multiple expansile bone lesions exhibiting a "ground-glass" matrix on radiographs. This syndrome is caused by a somatic activating mutation in which of the following genes?
. GNAS
. EXT1
. NF1
. PTEN
. SH3BP2

Correct Answer & Explanation

. GNAS

Explanation

The patient has McCune-Albright syndrome, characterized by polyostotic fibrous dysplasia, precocious puberty, and "coast of Maine" café-au-lait spots. It is caused by a somatic, post-zygotic activating mutation in the GNAS gene.

Question 408

Topic: Bone Tumors

An 8-year-old boy sustains a low-energy fracture of the proximal humerus. Radiographs show a centrally located, completely radiolucent metaphyseal lesion with a piece of cortical bone resting dependently at the bottom of the cyst cavity. What is this pathognomonic radiographic sign called?

. Shepherd's crook sign
. Fallen leaf sign
. Sunburst pattern
. Onion-skinning
. Popcorn calcification

Correct Answer & Explanation

. Fallen leaf sign

Explanation

The "fallen leaf" or "fallen fragment" sign occurs when a piece of fractured cortex falls through the fluid-filled cavity to the dependent portion of the lesion. It is highly specific for a unicameral (simple) bone cyst.

Question 409

Topic: Bone Tumors

A 16-year-old boy presents with severe nocturnal thigh pain that is completely relieved by ibuprofen. Imaging shows a 1 cm radiolucent nidus surrounded by dense reactive sclerosis in the femoral diaphysis. What is the primary mechanism of pain relief by NSAIDs in this condition?

. Inhibition of COX-2 mediated prostaglandin E2 (PGE2) production by the nidus
. Direct reduction of intraosseous pressure within the medullary canal
. Suppression of osteoclastic bone resorption at the sclerotic rim
. Inhibition of substance P release in the surrounding periosteum
. Vasoconstriction of feeding vessels to the nidus

Correct Answer & Explanation

. Inhibition of COX-2 mediated prostaglandin E2 (PGE2) production by the nidus

Explanation

Osteoid osteomas characteristically produce high levels of prostaglandin E2 (PGE2) due to intense COX-2 expression within the nidus. NSAIDs relieve pain by directly inhibiting this COX-mediated PGE2 production.

Question 410

Topic: Bone Tumors

A 25-year-old patient presents with a "shepherd's crook" deformity of the proximal femur. Radiographs show an expansile lesion with a "ground-glass" appearance. A somatic activating mutation in which of the following genes is characteristic of this condition?

. GNAS
. EXT1
. RB1
. TP53
. FGFR3

Correct Answer & Explanation

. GNAS

Explanation

Fibrous dysplasia is caused by a post-zygotic, somatic activating mutation in the GNAS gene. This leads to increased intracellular cAMP, which impairs the normal differentiation of bone-forming cells.

Question 411

Topic: Bone Tumors

An 18-year-old male complains of severe nocturnal thigh pain that is completely relieved by ibuprofen. Radiographs show a 1.0 cm radiolucent nidus surrounded by dense reactive sclerosis in the femoral diaphysis. The intense pain is pathogenically caused by the secretion of which substance by the nidus?

. Interleukin-1 (IL-1)
. Tumor necrosis factor-alpha (TNF-alpha)
. Prostaglandin E2 (PGE2)
. Bone morphogenetic protein-2 (BMP-2)
. Vascular endothelial growth factor (VEGF)

Correct Answer & Explanation

. Prostaglandin E2 (PGE2)

Explanation

Osteoid osteomas secrete high levels of Prostaglandin E2 (PGE2) and cyclooxygenase-2 (COX-2) from the nidus. This causes intense local inflammation and nocturnal pain, explaining the dramatic symptomatic relief achieved with NSAIDs.

Question 412

Topic: Bone Tumors

A 10-year-old girl is evaluated for a severe shepherd's crook deformity of the proximal femur and precocious puberty. Radiographs show extensive 'ground-glass' opacities in the affected bone. The pathogenesis of her underlying musculoskeletal condition is directly related to which of the following molecular mechanisms?

. Constitutive activation of adenylyl cyclase via a stimulatory G-protein
. Inactivating mutation of the PHEX gene
. Loss of function in the tumor suppressor gene PTEN
. Defective synthesis of Type I collagen
. Abnormal fibroblast growth factor receptor 3 (FGFR3) signaling

Correct Answer & Explanation

. Constitutive activation of adenylyl cyclase via a stimulatory G-protein

Explanation

The patient has McCune-Albright syndrome, which includes polyostotic fibrous dysplasia. This is caused by an activating post-zygotic somatic mutation in the GNAS gene, leading to constitutive activation of adenylyl cyclase and elevated intracellular cAMP.

Question 413

Topic: Bone Tumors

A 14-year-old boy complains of intense thigh pain that worsens at night and is dramatically relieved by ibuprofen. Imaging reveals a 1 cm radiolucent nidus surrounded by dense sclerotic bone in the proximal femur. Which of the following biochemical mediators is secreted in excess by the central nidus?

. Interleukin-1
. Prostaglandin E2
. Tumor necrosis factor-alpha
. Vascular endothelial growth factor
. Fibroblast growth factor 23

Correct Answer & Explanation

. Prostaglandin E2

Explanation

Osteoid osteomas typically produce high levels of Prostaglandin E2 (PGE2) and cyclooxygenase-2 (COX-2) within the central nidus. This robust production accounts for the profound localized pain that is classically responsive to NSAIDs.

Question 414

Topic: Bone Tumors

A 9-year-old boy presents with mild shoulder pain after throwing a baseball. Radiographs reveal a centrally located, purely lytic lesion in the proximal humeral metaphysis. A small cortical fragment is seen resting at the dependent portion of the radiolucent cavity. What is the most likely diagnosis?

. Aneurysmal bone cyst
. Chondroblastoma
. Unicameral bone cyst
. Osteosarcoma
. Eosinophilic granuloma

Correct Answer & Explanation

. Unicameral bone cyst

Explanation

The 'fallen leaf' or 'fallen fragment' sign on a radiograph represents a piece of fractured cortex resting at the bottom of a fluid-filled cavity. This sign is highly specific for a Unicameral (Simple) Bone Cyst complicated by a pathologic fracture.

Question 415

Topic: Bone Tumors

A 16-year-old male presents with a 6-month history of chronic, dull back pain that is not completely relieved by NSAIDs. Radiographs reveal an expansile, lytic lesion in the posterior elements of L3.

What is the most likely diagnosis?

. Aneurysmal Bone Cyst
. Osteoid Osteoma
. Osteosarcoma
. Osteoblastoma
. Ewing Sarcoma

Correct Answer & Explanation

. Osteoblastoma

Explanation

Osteoblastomas frequently involve the posterior elements of the spine and are classically larger than 2 cm. Unlike osteoid osteomas, the pain is typically less responsive to NSAIDs and less likely to be strictly nocturnal.

Question 416

Topic: Bone Tumors

A 9-year-old boy sustains a minor fall and presents with arm pain. Radiographs reveal a centrally located, lytic metaphyseal lesion in the proximal humerus with a 'fallen leaf' sign. Aspiration yields clear, yellow fluid. What is the most likely diagnosis?

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

Correct Answer & Explanation

. Unicameral bone cyst

Explanation

Unicameral (simple) bone cysts are fluid-filled, centrally located metaphyseal lesions commonly found in the proximal humerus or femur. A 'fallen leaf' sign represents a fractured piece of cortex settling at the bottom of the cystic cavity.

Question 417

Topic: Bone Tumors

A 17-year-old male presents with chronic dull, aching back pain that is not completely relieved by NSAIDs. Imaging shows a 2.5 cm expansile lytic lesion in the posterior elements of L3.

What is the most likely diagnosis?

. Osteoid osteoma
. Osteoblastoma
. Aneurysmal bone cyst
. Eosinophilic granuloma
. Osteosarcoma

Correct Answer & Explanation

. Osteoblastoma

Explanation

Osteoblastoma typically presents as an expansile lesion greater than 2 cm in the posterior elements of the spine. Unlike osteoid osteoma, the pain is less classically nocturnal and less completely responsive to NSAIDs.

Question 418

Topic: Bone Tumors

Which of the following radiographic findings is most characteristic of an aggressive osteoblastoma rather than conventional osteosarcoma?

. Codman triangle
. Sunburst periosteal reaction
. Expansile lesion with a thin shell of reactive periosteal bone
. Skip metastases in the same bone
. Cloud-like matrix mineralization in the soft tissue

Correct Answer & Explanation

. Expansile lesion with a thin shell of reactive periosteal bone

Explanation

Aggressive osteoblastoma often presents as a large, expansile lesion with a thin peripheral shell of reactive bone. Conventional osteosarcoma classically shows more destructive features like Codman's triangle or a sunburst reaction.

Question 419

Topic: Bone Tumors

A 12-year-old boy with Multiple Hereditary Exostoses (MHE) is evaluated for a rapidly growing, painful lesion on his proximal humerus. Mutations in EXT1 and EXT2 genes are implicated in MHE. These genes normally encode enzymes responsible for the synthesis of which molecule?

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

Correct Answer & Explanation

. Heparan sulfate

Explanation

EXT1 and EXT2 genes encode glycosyltransferases essential for the polymerization of heparan sulfate. Defects in this pathway disrupt normal physeal signaling, leading to osteochondroma formation.

Question 420

Topic: Bone Tumors
A 14-year-old girl presents with precocious puberty, café-au-lait macules with irregular 'coast of Maine' borders, and multiple lytic bone lesions with a ground-glass appearance. Histologic examination of the bone lesions would most likely reveal:
. Loose fibrovascular connective tissue intermixed with irregular osteoid and osteoblastic rimming
. Curvilinear trabeculae of woven bone lacking osteoblastic rimming in a fibrous stroma
. Multinucleated giant cells in a background of mononuclear stromal cells
. Nests of small round blue cells with positive CD99 staining
. Chondrocytes arranged in lobules with a permeative pattern

Correct Answer & Explanation

. Curvilinear trabeculae of woven bone lacking osteoblastic rimming in a fibrous stroma

Explanation

The clinical presentation is classic for McCune-Albright syndrome, which features polyostotic fibrous dysplasia. Histologically, fibrous dysplasia exhibits irregular trabeculae of woven bone (Chinese character pattern) in a fibrous stroma, characteristically lacking osteoblastic rimming.

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