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Bone Tumors MCQs

Practice Set 29 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 561

Topic: Bone Tumors

A 65-year-old male presents with a pathologic fracture of the proximal humerus. Radiographs show a distinct "punched-out" lytic lesion. Laboratory tests reveal an M-spike on serum protein electrophoresis. Which of the following imaging modalities is the most appropriate next step for staging the skeletal extent of this disease?

. Technetium-99m bone scan
. Whole-body low-dose CT or skeletal survey
. Gallium-67 scan
. Indium-111 WBC scan
. Ultrasound of the long bones

Correct Answer & Explanation

. Technetium-99m bone scan

Explanation

Whole-body low-dose CT is now the standard for staging the skeletal involvement of multiple myeloma, replacing the traditional radiographic skeletal survey. Technetium-99m bone scans rely on osteoblastic activity and often produce false negatives in purely lytic myeloma lesions.

Question 562

Topic: Bone Tumors

A 19-year-old male complains of severe, aching pain in his right proximal tibia that is worse at night and dramatically relieved by NSAIDs. Imaging shows a 1 cm radiolucent nidus surrounded by dense sclerotic bone. What is the most appropriate definitive management if medical therapy fails?

. Wide en bloc resection
. Chemotherapy followed by curettage
. Percutaneous radiofrequency ablation
. External beam radiation
. Intralesional steroid injection

Correct Answer & Explanation

. Wide en bloc resection

Explanation

The clinical presentation is classic for an osteoid osteoma. If medical management with NSAIDs fails or is poorly tolerated, percutaneous radiofrequency ablation is the gold standard definitive treatment due to its high success rate and low morbidity.

Question 563

Topic: Bone Tumors

A 14-year-old girl sustains a minor fall and complains of persistent arm pain. Radiographs show an expansile, multiloculated, radiolucent lesion in the metaphysis of the humerus. MRI demonstrates multiple fluid-fluid levels. Genetic analysis of the biopsy tissue is most likely to reveal a rearrangement involving which of the following genes?

. GNAS
. USP6
. IDH1
. EXT1
. BRAF

Correct Answer & Explanation

. GNAS

Explanation

Primary Aneurysmal Bone Cysts (ABCs) are now recognized as true neoplasms driven by translocations involving the USP6 gene on chromosome 17p13. The most common translocation is t(16;17)(q22;p13), fusing CDH11 to USP6. GNAS is mutated in fibrous dysplasia. IDH1/2 are mutated in enchondromas and chondrosarcomas. EXT1/EXT2 are mutated in osteochondromas. BRAF mutations are seen in Langerhans cell histiocytosis and non-ossifying fibromas.

Question 564

Topic: Bone Tumors
A 9-year-old girl presents with a limp and a discrepancy in leg length. Radiographs demonstrate a 'ground-glass' appearance in the proximal femur with a 'shepherd's crook' deformity. She is also noted to have large, irregular hyperpigmented macules on her trunk. Which endocrine abnormality is most commonly associated with this patient's condition?
. Precocious puberty
. Hyperparathyroidism
. Hypothyroidism
. Adrenal insufficiency
. Diabetes insipidus

Correct Answer & Explanation

. Precocious puberty

Explanation

The patient has McCune-Albright syndrome, which is characterized by the triad of polyostotic fibrous dysplasia, café-au-lait spots (with irregular 'coast of Maine' borders), and endocrine hyperfunction. The most common endocrinopathy is precocious puberty, although hyperthyroidism, growth hormone excess, and Cushing syndrome can also occur. The syndrome is caused by a post-zygotic activating mutation in the GNAS gene, leading to mosaicism.

Question 565

Topic: Bone Tumors

A 40-year-old woman is incidentally found to have a well-circumscribed, lobulated, cartilaginous lesion in the proximal humerus with punctate calcifications. There is no endosteal scalloping or cortical breakthrough. Molecular testing of such lesions frequently demonstrates mutations in which of the following enzymes?

. Succinate dehydrogenase
. Isocitrate dehydrogenase
. Malate dehydrogenase
. Fumarate hydratase
. Cytochrome c oxidase

Correct Answer & Explanation

. Succinate dehydrogenase

Explanation

Somatic mutations in the isocitrate dehydrogenase 1 or 2 (IDH1 or IDH2) genes are found in the majority of solitary enchondromas and central chondrosarcomas. These mutations lead to the production of an oncometabolite, 2-hydroxyglutarate (2-HG), which alters DNA methylation and promotes tumorigenesis. Multiple enchondromatosis (Ollier disease and Maffucci syndrome) is also associated with IDH1/2 mutations.

Question 566

Topic: Bone Tumors
A 10-year-old girl is evaluated for a limp and a leg-length discrepancy. Radiographs show a 'shepherd's crook' deformity of the proximal femur with 'ground-glass' opacities. Physical exam reveals large, irregular café-au-lait macules. What is the underlying molecular mechanism of her condition?
. Constitutive activation of adenylyl cyclase due to a GNAS missense mutation
. Loss of function of the tumor suppressor gene EXT1
. Overexpression of RANKL leading to excessive osteoclastogenesis
. Defect in type I collagen synthesis due to COL1A1 mutation
. Translocation resulting in the USP6 fusion oncogene

Correct Answer & Explanation

. Constitutive activation of adenylyl cyclase due to a GNAS missense mutation

Explanation

McCune-Albright syndrome consists of polyostotic fibrous dysplasia, café-au-lait spots, and endocrinopathies. It is caused by an activating missense mutation in the GNAS gene, leading to excessive cAMP production.

Question 567

Topic: Bone Tumors

A 20-year-old man presents with an aching back pain that is poorly relieved by NSAIDs. Imaging reveals a 3.5 cm lytic lesion with a sclerotic rim in the posterior elements of L3. Histology shows irregular osteoid trabeculae lined by plump osteoblasts in a highly vascular stroma. What is the most likely diagnosis?

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

Correct Answer & Explanation

. Osteoblastoma

Explanation

Osteoblastoma is histologically identical to osteoid osteoma but is distinguished by a size greater than 2 cm, progressive pain less responsive to NSAIDs, and a higher propensity for progressive growth.

Question 568

Topic: Bone Tumors
An 8-year-old girl presents with a limp and shortening of the left leg. Radiographs reveal multiple expansive, purely lytic lesions with a 'ground-glass' appearance in her left femur and tibia. Physical exam notes large, irregular café-au-lait macules with 'coast of Maine' borders, and she has signs of precocious puberty. Which of the following gene mutations is responsible for this condition?
. GNAS
. EXT1
. SQSTM1
. USP6
. TP53

Correct Answer & Explanation

. GNAS

Explanation

McCune-Albright syndrome is characterized by polyostotic fibrous dysplasia, café-au-lait macules, and endocrinopathies like precocious puberty. It is caused by an early postzygotic, activating mutation in the GNAS gene, leading to increased intracellular cAMP.

Question 569

Topic: Bone Tumors

A 9-year-old girl is evaluated for a limp and a leg length discrepancy. Physical examination reveals large, irregularly bordered cafe-au-lait spots. Radiographs of the femur demonstrate a "ground-glass" appearance and a "shepherd's crook" deformity. An activating mutation in which of the following genes is responsible for this condition?

. GNAS
. EXT1
. NF1
. SQSTM1
. USP6

Correct Answer & Explanation

. GNAS

Explanation

This presentation is classic for McCune-Albright syndrome, which features polyostotic fibrous dysplasia, cafe-au-lait macules, and endocrinopathies. It is caused by an activating post-zygotic somatic mutation in the GNAS gene.

Question 570

Topic: Bone Tumors

A 12-year-old girl presents with a "shepherd's crook" deformity of the proximal femur.

Radiographs show a classic ground-glass appearance. The underlying condition is driven by a genetic mutation that results in the constitutive activation of which of the following?

. Gs-alpha protein
. Fibroblast growth factor receptor 3 (FGFR3)
. Type I collagen (COL1A1)
. Runt-related transcription factor 2 (Runx2)
. Cartilage oligomeric matrix protein (COMP)

Correct Answer & Explanation

. Gs-alpha protein

Explanation

The clinical picture describes fibrous dysplasia. This condition is caused by a somatic activating mutation in the GNAS gene, which encodes the stimulatory G-protein alpha subunit (Gs-alpha), leading to increased intracellular cAMP.

Question 571

Topic: Bone Tumors
A 14-year-old girl is evaluated for a 'shepherd's crook' deformity of her proximal femur. Radiographs show a ground-glass intramedullary lesion. She also has multiple café-au-lait spots with irregular borders and a history of precocious puberty. What is the underlying genetic mechanism of her disease?
. Loss of heterozygosity of the EXT1 gene
. Activating mutation of the GNAS1 gene
. Inactivating mutation of the PTEN gene
. Amplification of the MDM2 gene
. Mutation in the SQSTM1 gene

Correct Answer & Explanation

. Activating mutation of the GNAS1 gene

Explanation

The patient has McCune-Albright syndrome, characterized by polyostotic fibrous dysplasia, 'coast of Maine' café-au-lait spots, and endocrinopathies. This is caused by an activating post-zygotic somatic mutation in the GNAS (GNAS1) gene, leading to overproduction of intracellular cAMP.

Question 572

Topic: Bone Tumors

An 18-year-old male complains of severe, progressively worsening nocturnal thigh pain that is completely relieved by ibuprofen. Radiographs reveal a cortical thickening with a 7mm radiolucent nidus. Which of the following is true regarding the pathophysiology of his pain?

. High levels of prostaglandin E2 (PGE2) produced by the nidus
. Rapid expansion of the periosteum due to aggressive woven bone formation
. Microfractures secondary to weakened cortical bone
. Release of histamine from mast cells within the lesion
. Direct nerve compression by the expanding mineralized matrix

Correct Answer & Explanation

. High levels of prostaglandin E2 (PGE2) produced by the nidus

Explanation

Osteoid osteomas produce high levels of prostaglandins (specifically PGE2 and prostacyclin) due to significantly increased COX-2 expression in the nidus. This chemical mediator causes the intense, unremitting nocturnal pain that is characteristically responsive to NSAIDs.

Question 573

Topic: Bone Tumors

A 25-year-old woman presents with a slow-growing mass on the posterior aspect of her distal femur. Radiographs show a heavily ossified, broad-based mass originating from the cortical surface without medullary involvement. Histology reveals low-grade spindle cells with abundant osteoid formation. What is her expected 5-year survival with wide surgical resection alone?

. Less than 20%
. 40-50%
. 60-70%
. Greater than 90%
. Virtually 0% without systemic chemotherapy

Correct Answer & Explanation

. Less than 20%

Explanation

Parosteal osteosarcoma is a low-grade surface osteosarcoma typically arising posterior to the distal femur. Because of its low grade and indolent behavior, wide surgical resection alone is often curative, yielding a greater than 90% 5-year survival rate. Adjuvant chemotherapy is generally not required unless there is evidence of dedifferentiation.

Question 574

Topic: Bone Tumors

A 68-year-old male with a long history of increasing hat size and bowing of his femurs presents with new, severe mid-thigh pain and a rapidly enlarging mass. Radiographs show a destructive lytic lesion in the bowed femur. What is the most likely histologic finding in the pre-existing bone?

. Thickened trabeculae with a mosaic pattern of prominent cement lines
. Extensive replacement of bone by fibrous tissue lacking osteoblastic rimming
. Thin, osteopenic trabeculae with unmineralized osteoid seams
. Avascular necrosis with empty lacunae
. Cartilage-capped bony exostoses

Correct Answer & Explanation

. Thickened trabeculae with a mosaic pattern of prominent cement lines

Explanation

The patient has secondary osteosarcoma arising in Paget disease of bone. Paget disease is characterized histologically by chaotic bone remodeling resulting in thickened trabeculae with haphazard, intersecting cement lines forming a 'mosaic' or 'jigsaw puzzle' pattern.

Question 575

Topic: Bone Tumors

A 16-year-old boy presents with worsening night pain in his tibia that is dramatically relieved by NSAIDs. Radiographs show a 1 cm radiolucent nidus surrounded by dense reactive sclerosis. If excised, histologic examination of the nidus is most likely to demonstrate which of the following?

. A network of woven bone trabeculae lined by prominent osteoblasts in a highly vascular stroma
. Lobules of hyaline cartilage with scattered binucleated chondrocytes
. Woven bone lacking osteoblastic rimming in a bland fibrous stroma
. Sheets of uniform small blue cells with minimal cytoplasm
. Osteoid production surrounded by highly pleomorphic, hyperchromatic cells

Correct Answer & Explanation

. A network of woven bone trabeculae lined by prominent osteoblasts in a highly vascular stroma

Explanation

The clinical scenario is classic for an osteoid osteoma. Histologically, the nidus of an osteoid osteoma consists of interconnected, disorganized trabeculae of woven bone (osteoid) rimmed by plump, active osteoblasts, set within a highly vascular connective tissue stroma containing numerous nerve fibers (which mediate the intense pain via prostaglandins).

Question 576

Topic: Bone Tumors
Fibrous dysplasia is associated with a post-zygotic, somatic activating mutation in the GNAS gene. This genetic alteration directly results in the constitutive activation of which of the following intracellular signaling mechanisms?
. Inhibition of the Wnt/beta-catenin pathway
. Increased production of cyclic AMP (cAMP)
. Upregulation of the PI3K/AKT/mTOR cascade
. Overactivation of the MAP kinase pathway
. Suppression of SMAD signaling via TGF-beta

Correct Answer & Explanation

. Increased production of cyclic AMP (cAMP)

Explanation

Fibrous dysplasia (and McCune-Albright syndrome when associated with endocrinopathies and café-au-lait spots) is caused by a mutation in the GNAS gene, which encodes the alpha subunit of the stimulatory G protein (Gs-alpha). The activating mutation results in loss of GTPase activity, leading to constitutive activation of adenylate cyclase and persistently elevated intracellular levels of cyclic AMP (cAMP). This alters the differentiation of skeletal progenitor cells.

Question 577

Topic: Bone Tumors

A 14-year-old boy presents with aching pain in his proximal tibia that is significantly worse at night and rapidly relieved by ibuprofen. Radiographs demonstrate a radiolucent nidus less than 1.5 cm surrounded by reactive sclerosis. Which biochemical mediator is produced in exceptionally high quantities by the cells within this nidus?

. Interleukin-1
. Prostaglandin E2
. Tumor Necrosis Factor-alpha
. Bone Morphogenetic Protein-2
. Transforming Growth Factor-beta

Correct Answer & Explanation

. Interleukin-1

Explanation

Osteoid osteomas secrete high levels of Prostaglandin E2 due to increased expression of COX-2 enzymes in the nidus. This accounts for the intense night pain that is characteristically relieved by NSAIDs.

Question 578

Topic: Bone Tumors

A 12-year-old boy presents with a 'shepherd's crook' deformity of his proximal femur. Radiographs demonstrate an expansive, intramedullary ground-glass lesion. What is the underlying cellular mechanism driving the pathogenesis of this osseous lesion?

. Loss of function of EXT1 causing disordered physeal growth
. Constitutive activation of Gs-alpha leading to increased intracellular cAMP
. Overexpression of CSF-1 resulting in giant cell recruitment
. Mutation of the RET proto-oncogene causing osteoblast proliferation
. Inactivation of PTEN promoting uncontrolled osteoclast activity

Correct Answer & Explanation

. Loss of function of EXT1 causing disordered physeal growth

Explanation

The patient has fibrous dysplasia, caused by a post-zygotic activating mutation in the GNAS gene. This results in constitutive activation of the Gs-alpha protein, elevating cAMP levels and preventing the differentiation of osteoprogenitor cells.

Question 579

Topic: Bone Tumors

A 68-year-old man presents with severe generalized back pain, normocytic anemia, and hypercalcemia. Radiographs show multiple punched-out lytic skull lesions. Which of the following imaging modalities is generally considered the LEAST sensitive for detecting the extent of skeletal involvement in this specific disease process?

. Skeletal survey (plain radiographs)
. Whole-body low-dose CT
. Technetium-99m bone scan
. MRI of the spine and pelvis
. PET-CT scan

Correct Answer & Explanation

. Skeletal survey (plain radiographs)

Explanation

In multiple myeloma, the neoplastic plasma cells secrete factors (like DKK1) that inhibit osteoblast activity. Therefore, a Technetium-99m bone scan, which relies on osteoblastic radiotracer uptake, is frequently falsely negative and less sensitive than CT or MRI.

Question 580

Topic: Bone Tumors

A 19-year-old man presents with localized nighttime pain in his proximal femur that is dramatically relieved by ibuprofen. CT imaging reveals a 1-cm radiolucent nidus surrounded by dense reactive sclerosis. The nidus of this lesion is characterized by high levels of which of the following enzymes?

. Cyclooxygenase-2 (COX-2)
. Alkaline phosphatase
. Matrix metalloproteinase-9 (MMP-9)
. Tartrate-resistant acid phosphatase (TRAP)
. Lysyl oxidase

Correct Answer & Explanation

. Cyclooxygenase-2 (COX-2)

Explanation

Osteoid osteomas secrete high levels of prostaglandins (especially PGE2) secondary to robust COX-2 expression within the nidus osteoblasts. This pathogenesis explains the classic nocturnal pain that is highly responsive to NSAIDs.

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