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Bone Tumors MCQs

Practice Set 18 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 341

Topic: Bone Tumors

A 22-year-old man presents with a 6-month history of dull aching pain in his posterior thoracic spine. The pain is persistent and not reliably relieved by NSAIDs. A CT scan shows a 2.5-cm expansile radiolucent lesion in the posterior elements of T10 with surrounding reactive sclerosis. Histology shows interlacing trabeculae of woven bone with prominent osteoblastic rimming and vascular connective tissue, but no cellular atypia. Which of the following is the most likely diagnosis?

. Osteoid osteoma
. Osteoblastoma
. Aneurysmal bone cyst
. Osteosarcoma
. Chondroblastoma

Correct Answer & Explanation

. Osteoid osteoma

Explanation

The clinical and radiographic presentation is consistent with an osteoblastoma. Osteoblastomas are histologically identical to osteoid osteomas (interlacing woven bone trabeculae with osteoblastic rimming) but are distinguished clinically and radiographically by their larger size (>2.0 cm), distinct predilection for the posterior elements of the spine, and pain that is less consistently nocturnal or relieved by NSAIDs compared to the exquisite NSAID sensitivity of osteoid osteomas.

Question 342

Topic: Bone Tumors

A 16-year-old boy experiences severe, throbbing leg pain that is consistently worse at night and dramatically relieved by taking ibuprofen. Radiographs demonstrate a diaphyseal cortical thickening in the anterior tibia with a 5-mm radiolucent nidus. The intense pain associated with this specific bone lesion is primarily mediated by the local overproduction of which of the following substances?

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

Correct Answer & Explanation

. Prostaglandin E2 (PGE2)

Explanation

The clinical scenario is a classic presentation of an osteoid osteoma: a small (<1.5 cm) radiolucent nidus surrounded by reactive sclerotic bone, causing intense, unrelenting night pain that is exquisitely sensitive to nonsteroidal anti-inflammatory drugs (NSAIDs). The nidus of an osteoid osteoma produces massive amounts of Prostaglandin E2 (PGE2) and prostacyclin (often 100 to 1000 times the level of normal bone), along with increased expression of cyclooxygenase-2 (COX-2). PGE2 mediates the intense pain and local vasodilation.

Question 343

Topic: Bone Tumors
A 65-year-old man presents with generalized bone pain and a recent pathologic fracture of the proximal humerus. Laboratory studies show anemia, hypercalcemia, and renal insufficiency. Serum protein electrophoresis reveals a monoclonal spike. Which of the following is the most appropriate initial diagnostic imaging modality for staging his skeletal disease?
. Technetium-99m bone scan
. Whole-body low-dose CT (WBLDCT)
. Positron emission tomography (PET) scan
. Gadolinium-enhanced MRI of the humerus
. Single-photon emission computed tomography (SPECT)

Correct Answer & Explanation

. Whole-body low-dose CT (WBLDCT)

Explanation

Whole-body low-dose CT (WBLDCT) is now considered the standard of care and preferred initial imaging modality for detecting osteolytic bone lesions in multiple myeloma. Technetium-99m bone scans depend on osteoblastic activity, which is severely suppressed in myeloma, frequently leading to false-negative results.

Question 344

Topic: Bone Tumors

A 14-year-old girl presents with pain and swelling in her right shoulder. Radiographs demonstrate an expansile, eccentric lytic lesion in the proximal humerus metaphysis with a thin sclerotic rim. MRI shows multiple fluid-fluid levels. The pathogenesis of this lesion is most strongly associated with a rearrangement involving which of the following genes?

. GNAS
. EXT1
. USP6
. RUNX2
. TP53

Correct Answer & Explanation

. USP6

Explanation

Primary aneurysmal bone cysts (ABCs) are true neoplasms characterized by translocations causing the upregulation of the USP6 gene on chromosome 17p13. GNAS mutations are seen in fibrous dysplasia; EXT1/EXT2 are associated with multiple hereditary exostoses; RUNX2 is associated with cleidocranial dysplasia; and TP53 is associated with Li-Fraumeni syndrome.

Question 345

Topic: Bone Tumors
A 9-year-old girl is evaluated for a limp and a discrepancy in leg length. Radiographs reveal a 'shepherd's crook' deformity of the proximal femur with a 'ground-glass' appearance. She also has irregularly bordered hyperpigmented skin macules and a history of precocious puberty. This condition is caused by a somatic activating mutation resulting in the overproduction of which intracellular signaling molecule?
. Cyclic AMP (cAMP)
. Cyclic GMP (cGMP)
. Inositol triphosphate (IP3)
. Tyrosine kinase
. Beta-catenin

Correct Answer & Explanation

. Cyclic AMP (cAMP)

Explanation

McCune-Albright syndrome consists of polyostotic fibrous dysplasia, café-au-lait spots, and endocrine abnormalities. It is caused by a somatic mutation in the GNAS gene, which encodes the stimulatory G protein alpha subunit (Gsα). This mutation results in constitutive activation of adenylyl cyclase and unregulated overproduction of intracellular cAMP.

Question 346

Topic: Bone Tumors

A 22-year-old man presents with a 6-month history of left knee pain that is significantly worse at night. The pain is dramatically relieved within 30 minutes of taking ibuprofen. Radiographs reveal a 1-cm radiolucent nidus surrounded by dense, reactive sclerotic bone in the proximal tibial diaphysis. Which of the following inflammatory mediators is most responsible for this classic pain pattern?

. Interleukin-1 (IL-1)
. Tumor necrosis factor-alpha (TNF-alpha)
. Prostaglandin E2 (PGE2)
. Substance P
. Bradykinin

Correct Answer & Explanation

. Prostaglandin E2 (PGE2)

Explanation

The clinical scenario is classic for an osteoid osteoma. The intense night pain associated with osteoid osteomas is due to the local production of exceptionally high levels of prostaglandins, particularly Prostaglandin E2 (PGE2), by the nidus. Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit cyclooxygenase, effectively blocking PGE2 production and providing dramatic symptomatic relief.

Question 347

Topic: Bone Tumors

A 12-year-old boy is found to have an incidental lesion in the proximal humerus during a workup for shoulder stiffness. Radiographs show a centrally located, well-circumscribed radiolucent lesion in the metaphysis with mild cortical thinning. If a diagnostic aspiration of this intact lesion is performed, which of the following fluid characteristics is most classically expected?

. High amylase content
. Frank, uncoagulated blood
. Clear or serosanguineous fluid with high levels of prostaglandins
. Clear yellow fluid with high cholesterol content
. Purulent fluid with high polymorphonuclear cells

Correct Answer & Explanation

. Clear or serosanguineous fluid with high levels of prostaglandins

Explanation

The radiographic description strongly suggests a unicameral (simple) bone cyst (UBC). Aspiration of an intact UBC typically yields clear or serosanguineous fluid. Biochemical analysis of this cyst fluid reliably demonstrates significantly elevated levels of prostaglandins (especially PGE2), alkaline phosphatase, interleukins, and nitrogen. Frank blood would be more characteristic of an aneurysmal bone cyst.

Question 348

Topic: Bone Tumors

A 19-year-old man complains of a dull, aching pain in his right thigh that consistently worsens at night but is profoundly relieved by ibuprofen. CT imaging reveals a 0.8-cm radiolucent nidus surrounded by dense reactive cortical sclerosis in the femoral diaphysis. If a surgical resection is performed, histological analysis of the central nidus would most likely reveal which of the following?

. A mature cartilage cap undergoing endochondral ossification
. Blood-filled cavernous spaces separated by fibrous septa lacking endothelial lining
. Sheets of atypical chondrocytes within an abundant myxoid matrix
. Whorls of bland spindle cells in a dense collagenous background
. Interlacing trabeculae of woven bone lined by prominent, plump osteoblasts

Correct Answer & Explanation

. Interlacing trabeculae of woven bone lined by prominent, plump osteoblasts

Explanation

The clinical history and CT findings are pathognomonic for an osteoid osteoma. Histologically, the central nidus is composed of highly vascularized connective tissue containing interlacing trabeculae of osteoid (woven bone) lined by prominent, benign-appearing osteoblasts. Option A describes an osteochondroma. Option B is characteristic of an aneurysmal bone cyst. Option C describes a myxoid chondrosarcoma. Option D is typical of a benign fibrous lesion such as a non-ossifying fibroma.

Question 349

Topic: Bone Tumors

A 65-year-old woman is being evaluated for generalized bone pain, profound fatigue, and recent onset of hypercalcemia. Laboratory studies confirm a normocytic anemia, elevated serum creatinine, and a monoclonal spike on serum protein electrophoresis. Plain radiographs show multiple sharply marginated 'punched-out' lytic lesions in her skull and pelvis. If a technetium-99m bone scan is performed, which of the following findings is most likely?

. Diffuse uniformly increased radiotracer uptake throughout the axial skeleton
. Normal or 'cold' radiotracer uptake at the sites of the lytic lesions
. A 'superscan' appearance with absent renal radiotracer uptake
. Intensely increased focal uptake exclusively at the sites of the lytic lesions
. Asymmetric increased uptake isolated to the appendicular skeleton

Correct Answer & Explanation

. Normal or 'cold' radiotracer uptake at the sites of the lytic lesions

Explanation

The patient's presentation meets the CRAB criteria (Hypercalcemia, Renal failure, Anemia, Bone lesions) diagnostic of multiple myeloma. The lytic bone lesions in myeloma result from profound osteoclast activation mediated by myeloma cells, coupled with a striking suppression of osteoblast activity. Because technetium-99m methylene diphosphonate (Tc-99m MDP) bone scans rely on osteoblastic activity (new bone formation) to accumulate radiotracer, the purely osteolytic, osteoblast-suppressed lesions of multiple myeloma typically appear normal or 'cold' on a bone scan. Skeletal surveys or whole-body low-dose CT/MRI/PET are the preferred imaging modalities.

Question 350

Topic: Bone Tumors

A 15-year-old boy reports severe, throbbing right thigh pain that is worse at night and completely relieved by ibuprofen. A CT scan shows a 7-mm radiolucent nidus surrounded by dense sclerotic bone in the femoral diaphysis. What is the primary mediator responsible for the severe pain associated with this lesion?

. Interleukin-1 (IL-1)
. Tumor necrosis factor-alpha (TNF-alpha)
. Prostaglandin E2 (PGE2)
. Substance P
. Bradykinin

Correct Answer & Explanation

. Prostaglandin E2 (PGE2)

Explanation

The presentation is classic for an osteoid osteoma. The severe, nocturnal pain that is characteristically relieved by NSAIDs is caused by the high levels of Prostaglandin E2 (PGE2) produced by the nidus, which contains high concentrations of cyclooxygenase-2 (COX-2).

Question 351

Topic: Bone Tumors
A 25-year-old woman is evaluated for a limp and dull aching pain in her right hip. She has a history of precocious puberty and notes multiple hyperpigmented macules with irregular borders on her torso. Radiographs of the proximal right femur show an expansile, medullary, ground-glass lesion with a 'shepherd's crook' deformity. The underlying genetic mutation responsible for this patient's condition results in which of the following cellular derangements?
. Constitutive activation of the Gs-alpha protein
. Inactivation of the tumor suppressor gene p53
. Overexpression of the RUNX2 transcription factor
. Defective osteoclast ruffled border formation
. Decreased production of type I collagen

Correct Answer & Explanation

. Constitutive activation of the Gs-alpha protein

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 abnormalities (most commonly precocious puberty). The underlying pathogenesis is a post-zygotic somatic missense mutation in the GNAS1 gene. This mutation causes a loss of GTPase activity, leading to the constitutive activation of the Gs-alpha protein. This results in the overproduction of intracellular cyclic AMP (cAMP), which disrupts normal osteoblast differentiation and leads to the formation of immature, woven bone (fibrous dysplasia).

Question 352

Topic: Bone Tumors

An 18-year-old man complains of persistent mid-back pain that is worse at night. He reports that the pain is only partially relieved by ibuprofen. A CT scan of the thoracic spine demonstrates a well-circumscribed, 2.8-cm radiolucent nidus in the posterior elements of T12, surrounded by moderate reactive sclerosis. Based on the size and clinical characteristics of the lesion, what is the most likely diagnosis?

. Osteoid osteoma
. Osteoblastoma
. Aneurysmal bone cyst
. Osteosarcoma
. Chondroblastoma

Correct Answer & Explanation

. Osteoblastoma

Explanation

Osteoid osteoma and osteoblastoma are histologically identical benign bone-forming tumors. The primary distinction between the two is based on size and clinical behavior. Osteoblastomas are defined by a nidus that is larger than 1.5 to 2.0 cm (typically >2 cm). Clinically, osteoblastomas have a predilection for the posterior elements of the spine (similar to osteoid osteomas) but tend to be progressively enlarging and cause pain that is less consistently relieved by NSAIDs compared to the classic presentation of osteoid osteoma. Given the 2.8-cm nidus size, the correct diagnosis is osteoblastoma.

Question 353

Topic: Bone Tumors

A 14-year-old girl sustains a minor fall and reports persistent shoulder pain. Radiographs of the proximal humerus show a central, purely lytic lesion with cortical thinning. A 'fallen leaf' sign is noted. A needle is advanced into the lesion for aspiration and injection. What type of fluid is typically aspirated from this cyst?

. Serosanguineous fluid with extremely high alkaline phosphatase
. Clear yellow fluid with high levels of prostaglandins
. Pure venous blood under pulsatile pressure
. Purulent fluid with a high leukocyte count
. Viscous mucin with high hyaluronic acid content

Correct Answer & Explanation

. Clear yellow fluid with high levels of prostaglandins

Explanation

The clinical presentation and 'fallen leaf' (or fallen fragment) sign are pathognomonic for a unicameral bone cyst (UBC) or simple bone cyst, which has fractured. Fluid aspirated from an active UBC is typically clear or straw-colored (yellowish) and contains highly elevated levels of prostaglandins, particularly PGE2, which are believed to contribute to cyst expansion by stimulating bone resorption. Aneurysmal bone cysts typically yield dark blood under moderate pressure.

Question 354

Topic: Bone Tumors

A 19-year-old man presents with severe night pain in his right shin that is dramatically relieved by nonsteroidal anti-inflammatory drugs (NSAIDs). CT scan shows a 7-mm radiolucent nidus surrounded by dense reactive cortical sclerosis in the tibial diaphysis. If the patient elects for surgical intervention, what is the most appropriate definitive management?

. En bloc resection with wide margins
. Radiofrequency ablation (RFA)
. Radiation therapy
. Intralesional injection of corticosteroids
. Amputation

Correct Answer & Explanation

. Radiofrequency ablation (RFA)

Explanation

The clinical and radiographic presentation is classic for an osteoid osteoma (nidus < 1.5 cm, characteristic night pain relieved by NSAIDs). Radiofrequency ablation (RFA) is the current standard of care for definitive treatment of typical appendicular osteoid osteomas when non-operative management fails or the patient desires intervention. RFA is highly successful, less invasive, and avoids the structural weakening of the bone associated with open surgical excision.

Question 355

Topic: Bone Tumors
A 9-year-old girl is evaluated for a severe varus deformity of her proximal femur, described radiographically as a 'shepherd's crook'. She is noted to have large, irregular areas of skin hyperpigmentation on her trunk. Which of the following endocrine abnormalities is most commonly associated with this patient's underlying condition?
. Precocious puberty
. Hypothyroidism
. Hyperparathyroidism
. Adrenal insufficiency
. Type 1 diabetes mellitus

Correct Answer & Explanation

. Precocious puberty

Explanation

The patient has McCune-Albright syndrome, which is defined by the classic triad of polyostotic fibrous dysplasia (causing the 'shepherd's crook' deformity), café-au-lait spots with irregular 'coast of Maine' borders, and autonomous endocrine hyperfunction. The most common endocrine manifestation is precocious puberty. It is caused by a somatic activating mutation in the GNAS gene.

Question 356

Topic: Bone Tumors
A 20-year-old man presents with an aching left thigh pain that is notably worse at night and dramatically relieved by taking ibuprofen. Radiographs show a small radiolucent nidus (< 1.5 cm) surrounded by dense reactive sclerosis in the femoral diaphysis. Which of the following inflammatory mediators is produced in high levels by this lesion and mediates the characteristic pain?
. Interleukin-1 (IL-1)
. Tumor necrosis factor-alpha (TNF-a)
. Prostaglandin E2 (PGE2)
. Leukotriene B4 (LTB4)
. Matrix metalloproteinase-9 (MMP-9)

Correct Answer & Explanation

. Prostaglandin E2 (PGE2)

Explanation

The classic presentation of an osteoid osteoma is night pain relieved by NSAIDs or salicylates. The nidus contains osteoblasts that produce high concentrations of Prostaglandin E2 (PGE2) and cyclooxygenase-2 (COX-2) enzymes. The localized high concentration of PGE2 causes nerve irritation and the intense, characteristic nocturnal pain.

Question 357

Topic: Bone Tumors
A 9-year-old girl is evaluated for precocious puberty and several large café-au-lait spots with irregular 'coast of Maine' borders on her trunk. Radiographs of her femur demonstrate an expansile medullary lesion with a ground-glass appearance and severe varus bowing. A mutation in which of the following genes is most likely responsible for her condition?
. EXT1
. FGFR3
. GNAS1
. COL1A1
. NF1

Correct Answer & Explanation

. GNAS1

Explanation

The triad of polyostotic fibrous dysplasia (ground-glass bone lesions with 'shepherd's crook' bowing deformity), precocious puberty (or other endocrinopathies), and café-au-lait macules with irregular borders ('coast of Maine') defines McCune-Albright syndrome. It is caused by a postzygotic, activating somatic mutation in the GNAS1 gene, which encodes the alpha subunit of the Gs protein, leading to continuous cAMP production.

Question 358

Topic: Bone Tumors

A 19-year-old male presents with severe right thigh pain that is distinctly worse at night and dramatically relieved by over-the-counter ibuprofen. Radiographs reveal localized cortical thickening in the proximal femoral diaphysis with a central 7-mm radiolucent nidus. The dramatic pain relief provided by NSAIDs in this condition is directly mediated by the inhibition of which substance produced by the nidus?

. Prostaglandin E2 (PGE2)
. Tumor necrosis factor-alpha (TNF-a)
. Interleukin-1 (IL-1)
. Substance P
. Osteoprotegerin (OPG)

Correct Answer & Explanation

. Prostaglandin E2 (PGE2)

Explanation

The patient has an osteoid osteoma, characterized by a radiolucent nidus less than 1.5 cm and surrounding reactive sclerosis. The nidus contains osteoblasts that produce high levels of Prostaglandin E2 (PGE2), which directly mediates the intense nocturnal pain. NSAIDs provide dramatic relief by inhibiting cyclooxygenase (COX), thereby halting PGE2 synthesis.

Question 359

Topic: Bone Tumors
A 68-year-old woman presents with worsening intractable back pain and generalized fatigue. Investigations reveal normocytic anemia, hypercalcemia, and an elevated monoclonal M-protein spike on serum protein electrophoresis (SPEP). Suspecting multiple myeloma, what is the most sensitive and currently recommended whole-body imaging modality to assess the extent of skeletal osteolytic lesions in this patient?
. Technetium-99m methylene diphosphonate (Tc-99m MDP) bone scan
. Whole-body low-dose computed tomography (WBLDCT)
. Conventional full-body skeletal plain radiograph survey
. Single-photon emission computed tomography (SPECT)
. Dual-energy X-ray absorptiometry (DEXA) scan

Correct Answer & Explanation

. Whole-body low-dose computed tomography (WBLDCT)

Explanation

According to the International Myeloma Working Group (IMWG), Whole-Body Low-Dose CT (WBLDCT) is now the recommended first-line imaging modality for assessing skeletal involvement in multiple myeloma. It is far more sensitive than conventional skeletal surveys for detecting small osteolytic lesions. Technetium-99m bone scans are notoriously poor for myeloma because the lesions are purely osteoclastic/lytic and lack the osteoblastic activity required for radiotracer uptake.

Question 360

Topic: Bone Tumors
A 22-year-old woman sustains a pathologic fracture of her proximal femur. Pre-injury radiographs obtained from an outside hospital reveal a 'ground-glass' appearance of the medullary canal with a severe varus 'shepherd's crook' deformity. Physical examination notes large, irregular café-au-lait macules on her trunk. An activating somatic mutation in which of the following genes is fundamentally responsible for her condition?
. GNAS
. EXT1
. FGFR3
. PTH1R
. RET

Correct Answer & Explanation

. GNAS

Explanation

The patient presents with polyostotic fibrous dysplasia and café-au-lait macules (with irregular 'coast of Maine' borders), indicating McCune-Albright syndrome. Fibrous dysplasia is caused by a somatic, post-zygotic activating missense mutation in the GNAS gene. This gene encodes the alpha subunit of the stimulatory G protein (Gs-alpha). The mutation leads to constitutively increased intracellular cyclic AMP (cAMP), which disrupts the normal differentiation of osteoblasts, resulting in the characteristic proliferation of immature spindle cells and poorly formed woven bone (the 'ground-glass' appearance on radiographs).

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