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Bone Tumors MCQs

Practice Set 19 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 361

Topic: Bone Tumors

A 19-year-old man presents with right thigh pain that is worse at night and dramatically relieved by ibuprofen. CT scan shows a 9-mm radiolucent nidus surrounded by dense reactive bone in the lesser trochanter. If the patient is intolerant to long-term NSAID use, what is the most appropriate next step in management?

. Wide resection
. Marginal excision
. Percutaneous radiofrequency ablation
. Intralesional steroid injection
. External beam radiation therapy

Correct Answer & Explanation

. Percutaneous radiofrequency ablation

Explanation

The clinical presentation and radiographic findings are classic for an osteoid osteoma. While observation with NSAIDs is the first-line treatment for many patients, percutaneous radiofrequency ablation (RFA) is the gold standard surgical/interventional treatment in the appendicular skeleton when medical management fails or is not tolerated. It offers a highly successful, minimally invasive alternative to surgical resection.

Question 362

Topic: Bone Tumors

A 7-year-old boy presents with mild right arm pain after throwing a baseball. Radiographs show a centrally located, well-circumscribed radiolucent lesion in the proximal humeral metaphysis spanning the width of the medullary canal. A small fragment of bone is seen resting in the dependent portion of the cystic lesion. What is the most likely diagnosis?

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

Correct Answer & Explanation

. Unicameral bone cyst

Explanation

The description is classic for a unicameral bone cyst (UBC), also known as a simple bone cyst. They typically appear as central metaphyseal lytic lesions in the proximal humerus or proximal femur of children. The presence of a small piece of fractured cortex resting at the bottom of the fluid-filled cyst is known as the 'fallen leaf' or 'fallen fragment' sign and is considered pathognomonic for a UBC.

Question 363

Topic: Bone Tumors
A 9-year-old girl is evaluated for a leg length discrepancy and a progressive bowing deformity of her left femur. Radiographs show a 'shepherd's crook' deformity with ground-glass opacities in the proximal femur. Physical examination reveals multiple large café-au-lait spots with irregular 'coast of Maine' borders on her trunk. Which endocrinopathy is most commonly associated with her underlying condition?
. Precocious puberty
. Hypothyroidism
. Diabetes insipidus
. Hyperparathyroidism
. Cushing's disease

Correct Answer & Explanation

. Precocious puberty

Explanation

The patient has McCune-Albright syndrome, which is characterized by the classic triad of polyostotic fibrous dysplasia (producing the 'shepherd's crook' deformity and ground-glass appearance), café-au-lait macules with irregular borders, and hyperfunctioning endocrinopathies. The most common endocrine abnormality in this syndrome is gonadotropin-independent precocious puberty.

Question 364

Topic: Bone Tumors

A 21-year-old man presents with nocturnal thigh pain that is completely relieved by NSAIDs. Radiographs demonstrate a radiolucent nidus with surrounding dense reactive sclerosis in the femoral diaphysis.

Which of the following molecules is secreted in abnormally high concentrations by the nidus of this lesion, accounting for the characteristic pain pattern?

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

Correct Answer & Explanation

. Prostaglandin E2 (PGE2)

Explanation

The clinical and radiographic presentation describes an osteoid osteoma. The hallmark symptom is intense nocturnal pain that typically responds dramatically to nonsteroidal anti-inflammatory drugs (NSAIDs) or aspirin. This distinct clinical feature is due to the nidus of the osteoid osteoma producing high levels of prostaglandins, particularly Prostaglandin E2 (PGE2), up to 100 to 1,000 times normal tissue levels. NSAIDs block cyclooxygenase, inhibiting PGE2 synthesis and relieving the pain.

Question 365

Topic: Bone Tumors

An 18-year-old male presents with a 6-month history of dull, aching back pain that is worsened at night. He reports that the pain is only mildly relieved by ibuprofen. Imaging demonstrates a 2.5 cm radiolucent lesion with a central nidus located in the posterior elements of the L4 vertebra. Histology shows interlacing trabeculae of woven bone surrounded by prominent osteoblasts. What is the most likely diagnosis?

. Osteoid osteoma
. Aneurysmal bone cyst
. Osteoblastoma
. Osteochondroma
. Chondromyxoid fibroma

Correct Answer & Explanation

. Osteoblastoma

Explanation

The patient's presentation is most consistent with an osteoblastoma. While histologically identical to an osteoid osteoma (showing interlacing trabeculae of woven bone lined by prominent osteoblasts), an osteoblastoma is distinguished by its larger size (> 2 cm). Clinically, the pain associated with osteoblastoma is often less severe at night and less responsive to NSAIDs compared to osteoid osteoma. Both tumors have a predilection for the posterior elements of the spine.

Question 366

Topic: Bone Tumors
An 8-year-old girl sustains a minor fall and presents with a proximal femur fracture. Radiographs reveal a 'shepherd's crook' deformity of the proximal femur and a diaphyseal lesion with a 'ground-glass' appearance. The patient has a history of precocious puberty and has large, irregular café-au-lait macules on her trunk. What is the underlying pathophysiological mechanism of her bone disease?
. Constitutive activation of the Gs-alpha protein due to a missense mutation
. Deficiency of the enzyme tissue-nonspecific alkaline phosphatase (TNSALP)
. Impaired formation of the osteoclast ruffled border secondary to TCIRG1 mutation
. Defective synthesis of type I collagen due to COL1A1 or COL1A2 mutations
. Upregulation of fibroblast growth factor receptor 3 (FGFR3)

Correct Answer & Explanation

. Constitutive activation of the Gs-alpha protein due to a missense mutation

Explanation

The patient has McCune-Albright syndrome, a triad of polyostotic fibrous dysplasia, precocious puberty (or other endocrinopathies), and café-au-lait spots with irregular 'coast of Maine' borders. The underlying etiology is a somatic, post-zygotic missense mutation in the GNAS gene, which encodes the alpha subunit of the stimulatory G protein (Gs-alpha). This mutation leads to constitutive activation of adenylate cyclase, increased intracellular cAMP, and subsequent abnormal cellular proliferation and differentiation, resulting in the replacement of normal bone with immature fibrous tissue.

Question 367

Topic: Bone Tumors

A 25-year-old female presents with a painless mass on the posterior aspect of her distal thigh. Radiographs reveal a dense, extensively ossified mass attached to the posterior cortex of the distal femur via a broad base. Biopsy shows well-formed woven bone trabeculae within a bland fibrous stroma, with minimal cellular atypia. What is the most likely diagnosis and the most appropriate standard of care?

. Periosteal osteosarcoma; neoadjuvant chemotherapy and wide resection
. Osteochondroma; marginal excision
. High-grade surface osteosarcoma; neoadjuvant chemoradiation
. Parosteal osteosarcoma; wide resection alone
. Myositis ossificans; observation

Correct Answer & Explanation

. Parosteal osteosarcoma; wide resection alone

Explanation

Parosteal osteosarcoma is a low-grade surface osteosarcoma that classically presents on the posterior aspect of the distal femur in young adults. Radiographically, it appears as a dense, heavily ossified mass attached to the cortex. Unlike classic intramedullary high-grade osteosarcomas, parosteal osteosarcomas rarely require chemotherapy (unless dedifferentiation is identified). The definitive treatment is wide surgical resection alone.

Question 368

Topic: Bone Tumors

A 19-year-old man presents with localized right leg pain that is significantly worse at night and dramatically relieved within 30 minutes of taking ibuprofen. Imaging demonstrates a 7-mm radiolucent nidus surrounded by dense, reactive sclerotic bone in the anterior cortex of the mid-diaphyseal tibia. If the patient desires definitive treatment but wishes to avoid open surgery, which of the following is considered the standard of care?

. Radiofrequency ablation
. Cryotherapy
. Intralesional injection of methylprednisolone
. High-intensity focused ultrasound (HIFU)
. External beam radiation therapy

Correct Answer & Explanation

. Radiofrequency ablation

Explanation

The patient's clinical and radiographic presentation is classic for an osteoid osteoma. While observation with NSAIDs is an option (as lesions can spontaneously burn out over several years), radiofrequency ablation (RFA) is the definitive, minimally invasive treatment of choice. It has excellent success rates and has largely replaced surgical 'en bloc' or burr-down excision.

Question 369

Topic: Bone Tumors
A 12-year-old girl is evaluated for a prominent leg length discrepancy and a limp. She has a documented history of precocious puberty and has several large, irregular café-au-lait spots with jagged borders on her trunk. Radiographs of her proximal femur demonstrate a 'shepherd's crook' deformity with a ground-glass appearance of the medullary canal. A mutation in which of the following genes is the underlying cause of this patient's syndrome?
. EXT1
. NF1
. GNAS1
. FGFR3
. RUNX2

Correct Answer & Explanation

. GNAS1

Explanation

This patient has McCune-Albright syndrome, which is characterized by the triad of polyostotic fibrous dysplasia, endocrine abnormalities (most commonly precocious puberty), and café-au-lait macules with 'coast of Maine' (jagged) borders. It is caused by a sporadic, postzygotic activating mutation in the GNAS1 gene. This mutation encodes an abnormal alpha subunit of the stimulatory G protein (Gs), leading to continuous activation of adenylate cyclase and overproduction of intracellular cAMP.

Question 370

Topic: Bone Tumors

A 14-year-old boy presents with pain and swelling over his proximal humerus after minor trauma. Radiographs show an expansile, radiolucent, metaphyseal lesion. MRI demonstrates multiple fluid-fluid levels within the lesion. A core biopsy reveals blood-filled cavernous spaces lacking an endothelial lining. A cytogenetic abnormality in which of the following genes is most likely associated with the pathogenesis of this primary lesion?

. EXT1
. GNAS
. TP53
. USP6
. RB1

Correct Answer & Explanation

. USP6

Explanation

The clinical, radiographic, and histological findings describe an Aneurysmal Bone Cyst (ABC). Primary ABCs are now known to be true neoplasms driven by genetic translocations, most commonly involving the USP6 (ubiquitin specific peptidase 6) gene on chromosome 17p13. EXT1 is associated with hereditary multiple exostoses. GNAS mutations are found in fibrous dysplasia. TP53 and RB1 mutations are associated with osteosarcoma.

Question 371

Topic: Bone Tumors

A 19-year-old man reports a 6-month history of right thigh pain that is particularly severe at night and brings him out of sleep. He notes that taking over-the-counter ibuprofen provides dramatic and near-complete relief for several hours. Radiographs show profound diaphyseal cortical thickening with a 7-mm radiolucent nidus. The intense pain and the specific response to nonsteroidal anti-inflammatory drugs (NSAIDs) in this condition are directly related to the high local concentration of which of the following mediators?

. Interleukin-1 (IL-1)
. Tumor necrosis factor-alpha (TNF-alpha)
. Prostaglandin E2 (PGE2)
. Substance P
. Transforming growth factor-beta (TGF-beta)

Correct Answer & Explanation

. Prostaglandin E2 (PGE2)

Explanation

The presentation of night pain dramatically relieved by NSAIDs, combined with a small radiolucent nidus surrounded by dense reactive cortical bone, is pathognomonic for an osteoid osteoma. The nidus of an osteoid osteoma produces abnormally high levels of cyclooxygenase-2 (COX-2) and its downstream product, Prostaglandin E2 (PGE2). PGE2 mediates both the intense localized pain and the dense reactive bone formation surrounding the lesion. The dramatic pain relief provided by NSAIDs is directly attributable to their inhibition of COX, which halts PGE2 synthesis.

Question 372

Topic: Bone Tumors
A 62-year-old man presents with diffuse back and rib pain. Radiographs show multiple punched-out lytic lesions in the skull and pelvis. Laboratory evaluation reveals hypercalcemia, renal insufficiency, and anemia. Bone marrow aspirate shows >10% clonal plasma cells. Which of the following laboratory abnormalities is most strongly associated with a poor overall survival prognosis in this disease?
. Elevated serum calcium
. Decreased serum albumin
. Elevated serum beta-2 microglobulin
. Presence of Bence Jones proteins in the urine
. Elevated serum alkaline phosphatase

Correct Answer & Explanation

. Elevated serum beta-2 microglobulin

Explanation

The patient's presentation is diagnostic of multiple myeloma (CRAB criteria: hyperCalcemia, Renal insufficiency, Anemia, Bone lesions). The Revised International Staging System (R-ISS) for multiple myeloma relies heavily on serum beta-2 microglobulin and serum albumin levels, along with LDH and high-risk chromosomal abnormalities. An elevated beta-2 microglobulin (>5.5 mg/L) is the most significant biochemical indicator of high tumor burden, diminished renal function, and poor prognosis.

Question 373

Topic: Bone Tumors

A 20-year-old woman is incidentally found to have a proximal femoral lesion during imaging for a hip strain. The radiograph shows a diaphyseal 'ground-glass' appearance surrounded by a sclerotic rim, with mild varus bowing. She has no endocrine abnormalities or cafe-au-lait spots. The underlying genetic mutation for this bony lesion involves which of the following?

. GNAS1 mutation leading to increased cAMP
. EXT1 mutation leading to abnormal heparan sulfate synthesis
. RET proto-oncogene mutation
. APC gene mutation
. p53 mutation

Correct Answer & Explanation

. GNAS1 mutation leading to increased cAMP

Explanation

The radiographic description ('ground-glass' matrix, mild bowing deformity) is classic for fibrous dysplasia. Fibrous dysplasia (both monostotic and polyostotic forms, as well as McCune-Albright syndrome) is caused by a somatic, activating postzygotic mutation in the GNAS1 gene. This gene encodes the alpha subunit of the stimulatory G protein (Gs). The mutation causes constitutive activation of adenylate cyclase, leading to increased intracellular cAMP, which results in the abnormal differentiation of osteoblasts and replacement of normal medullary bone with fibrous stroma.

Question 374

Topic: Bone Tumors

A 16-year-old boy complains of persistent anterior thigh pain that has worsened over the past 4 months. He notes the pain is significantly worse at night and is dramatically relieved within 30 minutes of taking ibuprofen. Radiographs demonstrate a diaphyseal cortical thickening with a 1-cm central radiolucent nidus. What is the pathophysiologic mechanism responsible for the characteristic pain in this condition?

. Increased local concentration of prostaglandins, specifically PGE2
. Local compression of terminal branches of the femoral nerve
. Increased local production of interleukin-6 and TNF-alpha
. Rapid expansion of the periosteum due to aggressive tumor growth
. Accumulation of bradykinin in the surrounding muscle tissues

Correct Answer & Explanation

. Increased local concentration of prostaglandins, specifically PGE2

Explanation

The classic presentation of an osteoid osteoma includes intense, localized pain that is worse at night and dramatically relieved by NSAIDs. Pathologically, the central nidus of an osteoid osteoma produces very high levels of prostaglandins, particularly PGE2. This high local concentration of prostaglandins stimulates sensory nerve endings within the lesion, causing the intense pain. NSAIDs work by inhibiting cyclooxygenase (COX), thereby blocking prostaglandin synthesis and providing rapid pain relief.

Question 375

Topic: Bone Tumors

A 19-year-old man presents with severe right leg pain that is worse at night and dramatically improves with NSAIDs. Radiographs show a sclerotic lesion in the tibial diaphysis with a small central radiolucent nidus. The intense pain associated with this lesion is primarily mediated by high levels of which of the following within the nidus?

. Substance P
. Prostaglandin E2
. Interleukin-1
. Tumor necrosis factor-alpha
. Bradykinin

Correct Answer & Explanation

. Prostaglandin E2

Explanation

The clinical presentation is classic for an osteoid osteoma. The pain is characteristically severe, worse at night, and relieved by NSAIDs. This is because the nidus of an osteoid osteoma produces high levels of prostaglandins, particularly Prostaglandin E2 (PGE2), which mediates the pain response and local vasodilation. NSAIDs block the cyclooxygenase (COX) enzyme, thereby decreasing PGE2 production and relieving pain.

Question 376

Topic: Bone Tumors

A 12-year-old girl is evaluated for a noticeable leg length discrepancy and a limp. Radiographs of her left femur show an expansive, purely lytic lesion with a 'ground-glass' appearance and a characteristic 'shepherd's crook' deformity of the proximal femur. This condition is caused by a somatic activating mutation in which of the following?

. GNAS1 gene
. EXT1 gene
. FGFR3 gene
. RB1 gene
. p53 gene

Correct Answer & Explanation

. GNAS1 gene

Explanation

The clinical and radiographic findings describe fibrous dysplasia, specifically involving the proximal femur leading to a 'shepherd's crook' deformity. Fibrous dysplasia is caused by a somatic, activating missense mutation in the GNAS1 gene, which encodes the alpha subunit of the stimulatory G protein (Gs-alpha). This mutation leads to an overproduction of cAMP, affecting the differentiation of bone marrow stromal cells.

Question 377

Topic: Bone Tumors

A 9-year-old boy presents with a 3-month history of deep, aching pain in his proximal femur that worsens at night. He reports dramatic relief of his symptoms 30 minutes after taking ibuprofen. Radiographs and a CT scan reveal a 7-mm radiolucent nidus surrounded by dense, reactive cortical sclerosis. The intense pain experienced by this patient is most directly mediated by elevated levels of which of the following substances produced by the nidus?

. Interleukin-1
. Tumor necrosis factor-alpha
. Prostaglandin E2
. Substance P
. Bradykinin

Correct Answer & Explanation

. Prostaglandin E2

Explanation

The patient has a classic presentation of an osteoid osteoma. Osteoid osteomas secrete high levels of prostaglandins, particularly Prostaglandin E2 (PGE2), which mediates the severe pain and the characteristic vasodilation around the lesion. This is the physiological basis for the dramatic pain relief provided by nonsteroidal anti-inflammatory drugs (NSAIDs).

Question 378

Topic: Bone Tumors

A 35-year-old man presents with a locally aggressive, osteolytic lesion in the epiphysis of his distal radius. Histopathologic examination reveals abundant, evenly distributed multinucleated osteoclast-like giant cells in a background of round to oval mononuclear cells. Which of the following genetic alterations is highly specific for the neoplastic cells in this tumor?

. GNAS mutation
. H3F3A mutation
. EXT1 mutation
. IDH1 mutation
. PTEN mutation

Correct Answer & Explanation

. H3F3A mutation

Explanation

Giant cell tumor of bone (GCTB) is characterized by a high frequency of somatic mutations in the H3F3A gene, which encodes the histone H3.3 variant. This mutation (most commonly G34W) is found in the mononuclear neoplastic stromal cells, not the reactive giant cells, and is a highly specific diagnostic marker for GCTB. GNAS mutations are seen in fibrous dysplasia, EXT1/2 in osteochondromas, and IDH1/2 in enchondromas and chondrosarcomas.

Question 379

Topic: Bone Tumors

A 14-year-old girl presents with a rapidly enlarging mass in her proximal fibula. Radiographs reveal an eccentric, expansile, purely lytic metaphyseal lesion with a thin 'eggshell' cortical rim. MRI demonstrates multiple fluid-fluid levels. Genetic analysis of the primary lesion would most likely reveal a translocation involving which of the following genes?

. USP6
. EXT1
. GNAS
. RUNX2
. COL1A1

Correct Answer & Explanation

. USP6

Explanation

Primary Aneurysmal Bone Cysts (ABCs) are neoplastic processes characterized by translocations involving the USP6 gene on chromosome 17p13. EXT1 is associated with multiple hereditary exostoses. GNAS mutations are seen in fibrous dysplasia. RUNX2 mutations cause cleidocranial dysplasia. COL1A1 mutations are seen in osteogenesis imperfecta.

Question 380

Topic: Bone Tumors

A 22-year-old man has a 6-month history of a dull, aching pain in his posterior neck. He notes that the pain is constant and is not consistently relieved by over-the-counter NSAIDs. A CT scan of the cervical spine reveals a 2.5-cm radiolucent nidus surrounded by a thin rim of reactive sclerosis located in the posterior elements of C5. Histological examination of a biopsy specimen reveals interconnected, disorganized trabeculae of woven bone lined by prominent osteoblasts within a highly vascularized connective tissue stroma. What is the most likely diagnosis?

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

Correct Answer & Explanation

. Osteoblastoma

Explanation

The clinical, radiographic, and histological findings are indicative of an osteoblastoma. Histologically, osteoblastoma and osteoid osteoma appear virtually identical, characterized by a highly vascularized stroma and interlacing trabeculae of woven bone lined by numerous plump osteoblasts. They are primarily differentiated based on their clinical behavior and size. Osteoblastomas are classically larger than 2 cm in diameter and have a predilection for the posterior elements of the spine (similar to osteoid osteoma, but generally larger). Clinically, the pain associated with osteoblastoma is usually a dull ache that is less predictably nocturnal and is not as dramatically relieved by NSAIDs or salicylates compared to the classic presentation of osteoid osteoma. Aneurysmal bone cysts often have blood-filled cavernous spaces, while chondroblastoma typically occurs in the epiphysis and features chondroblasts with 'chicken-wire' calcifications.

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