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Bone Tumors MCQs

Practice Set 40 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 781

Topic: Bone Tumors

A 16-year-old boy presents with nocturnal thigh pain that is dramatically relieved by NSAIDs. Imaging reveals a 7mm radiolucent nidus surrounded by dense sclerosis in the femoral diaphysis. What is the biochemical basis for the profound pain relief with NSAIDs?

. The nidus produces high levels of Prostaglandin E2 (PGE2) which NSAIDs inhibit
. NSAIDs shrink the highly vascular nidus
. NSAIDs directly reduce periosteal reaction
. The nidus expresses high levels of COX-1 only
. NSAIDs induce apoptosis of the osteoblastic tumor cells

Correct Answer & Explanation

. The nidus produces high levels of Prostaglandin E2 (PGE2) which NSAIDs inhibit

Explanation

The classic night pain of an osteoid osteoma is mediated by extremely high levels of prostaglandins (specifically PGE2) produced by the nidus. NSAIDs inhibit cyclooxygenase (COX), drastically reducing PGE2 production and providing profound pain relief.

Question 782

Topic: Bone Tumors

A 16-year-old male presents with deep nocturnal aching in his proximal tibia that is dramatically relieved by ibuprofen. Radiographs show localized cortical thickening with a small 5mm radiolucent nidus. What is the primary mechanism by which the pharmacologic agent provides pain relief in this condition?

. Inhibition of osteoclast activity
. Inhibition of cyclooxygenase and decreasing prostaglandin E2 levels
. Selective blockade of mu-opioid receptors
. Reduction of local histamine release
. Direct inhibition of substance P in the dorsal root ganglion

Correct Answer & Explanation

. Inhibition of cyclooxygenase and decreasing prostaglandin E2 levels

Explanation

Osteoid osteomas produce high levels of prostaglandins (specifically PGE2) within the nidus, which cause the characteristic nocturnal pain. NSAIDs provide dramatic relief by inhibiting cyclooxygenase and decreasing local prostaglandin synthesis.

Question 783

Topic: Bone Tumors

A 19-year-old male reports persistent nocturnal thigh pain that is completely relieved by ibuprofen. Imaging reveals a 7mm radiolucent nidus surrounded by reactive sclerosis in the femoral diaphysis. What is the standard, minimally invasive definitive treatment?

. En bloc resection
. Curettage and bone grafting
. Radiofrequency ablation (RFA)
. Radiation therapy
. Long-term narcotic pain management

Correct Answer & Explanation

. Radiofrequency ablation (RFA)

Explanation

Radiofrequency ablation (RFA) is the current gold standard and least invasive definitive treatment for an osteoid osteoma. It provides excellent success rates with minimal morbidity compared to open surgical resection.

Question 784

Topic: Bone Tumors

A 13-year-old girl presents with right groin pain and the imaging and histology shown. The histology reveals irregular, woven bone trabeculae in a fibrous stroma without osteoblastic rimming ('Chinese letter' pattern). This condition is associated with a somatic activating mutation in which of the following genes?

. EXT1
. GNAS1
. RB1
. TP53
. FGFR3

Correct Answer & Explanation

. GNAS1

Explanation

Correct Answer: BThe clinical, radiographic (ground-glass appearance, Shepherd's crook deformity), and histologic ('Chinese letter' woven bone lacking osteoblastic rimming in a fibrous stroma) findings are diagnostic of fibrous dysplasia. Fibrous dysplasia is caused by a somatic, post-zygotic activating mutation in the GNAS1 gene, which encodes the alpha subunit of the stimulatory G protein (Gs-alpha), leading to increased intracellular cAMP and abnormal osteoblast differentiation.

Question 785

Topic: Bone Tumors

A 13-year-old girl presents with right groin pain. Radiographs reveal a ground-glass lesion in the proximal femur with a mild 'Shepherd's crook' deformity. Histologic examination demonstrates proliferating fibroblasts in a loose spindle cell background with dysplastic metaplastic trabeculae arranged in a 'Chinese letter' pattern. Which of the following is the most likely diagnosis?

. Unicameral bone cyst
. Aneurysmal bone cyst
. Fibrous dysplasia
. Chondromyxoid fibroma
. Osteofibrous dysplasia

Correct Answer & Explanation

. Fibrous dysplasia

Explanation

Correct Answer: Fibrous dysplasiaThe clinical, radiographic, and histologic findings are classic for fibrous dysplasia. Radiographically, it presents as a lytic, expansile lesion with a 'ground-glass' matrix, often leading to bowing deformities in the proximal femur known as a 'Shepherd's crook' deformity. Histologically, it is characterized by a fibrous stroma containing irregular, woven bone trabeculae that lack osteoblastic rimming, often described as having a 'Chinese letter' or 'alphabet soup' appearance.

Question 786

Topic: Bone Tumors

A 14-year-old girl presents with a painful mass in her proximal humerus. Imaging is provided, demonstrating an expansile, eccentric, lytic lesion with fluid-fluid levels on MRI. Following curettage and bone grafting, which of the following factors is most strongly associated with an increased risk of local recurrence?

. Patient age greater than 20 years
. Closed physes
. Young age and open physes
. Use of a high-speed burr during curettage
. Use of phenol as a local adjuvant

Correct Answer & Explanation

. Young age and open physes

Explanation

Correct Answer: Young age and open physesThe imaging is classic for an aneurysmal bone cyst (ABC), showing fluid-fluid levels on MRI. Factors associated with a higher rate of local recurrence include young age, open physes, and inadequate surgical margins. The use of a high-speed burr and local adjuvants (like phenol or argon beam) decreases the recurrence rate.

Question 787

Topic: Bone Tumors

A 16-year-old boy presents with nocturnal back pain relieved by NSAIDs. Imaging reveals a 7mm intracortical nidus in the lamina of L4, located 4 mm from the traversing L4 nerve root. Which of the following is the most appropriate definitive management?

. Radiofrequency ablation
. CT-guided percutaneous cryoablation
. Observation only
. Surgical excision (curettage)
. Neoadjuvant radiation

Correct Answer & Explanation

. Surgical excision (curettage)

Explanation

The diagnosis is an osteoid osteoma. While radiofrequency ablation (RFA) is the treatment of choice for most locations, it is contraindicated when the nidus is within 1 cm of critical neural elements due to the risk of thermal nerve injury. Surgical excision is required.

Question 788

Topic: Bone Tumors
A 25-year-old female presents with a progressive "shepherd's crook" deformity of her right proximal femur. She also reports a history of precocious puberty and has large, irregular café-au-lait macules. This condition is caused by a mutation in the GNAS gene, leading to overactivity of which cellular messenger?
. cGMP
. cAMP
. Calcium
. Inositol triphosphate (IP3)
. Diacylglycerol (DAG)

Correct Answer & Explanation

. cAMP

Explanation

McCune-Albright syndrome (polyostotic fibrous dysplasia, endocrinopathy, café-au-lait spots) is caused by a somatic activating mutation in the GNAS gene. This results in constitutive activation of adenylate cyclase and increased intracellular cAMP.

Question 789

Topic: Bone Tumors

A 19-year-old male presents with severe nocturnal pain in the proximal tibia that is completely relieved by oral ibuprofen. Imaging shows a 1.2 cm radiolucent nidus surrounded by thick cortical sclerosis. Which specific cell type is primarily responsible for the excessive prostaglandin E2 (PGE2) production in this lesion?

. Multinucleated giant cells
. Chondroblasts
. Osteoblasts within the nidus
. Fibroblasts in the reactive zone
. Reactive osteoclasts

Correct Answer & Explanation

. Osteoblasts within the nidus

Explanation

The lesion is an osteoid osteoma. The intense pain is mediated by high levels of prostaglandin E2 (PGE2), which is secreted directly by the neoplastic osteoblasts residing within the nidus.

Question 790

Topic: Bone Tumors

A 12-year-old male presents with a mixed lytic and sclerotic metaphyseal lesion of the distal femur with a 'sunburst' periosteal reaction. He has a history of poikiloderma, sparse hair, and bilateral cataracts. Which gene mutation is most likely responsible for his underlying syndrome?

. TP53
. RB1
. RECQL4
. EXT1
. GNAS

Correct Answer & Explanation

. RECQL4

Explanation

The patient's presentation of osteosarcoma coupled with poikiloderma, alopecia, and cataracts is classic for Rothmund-Thomson syndrome. This autosomal recessive disorder is caused by a mutation in the RECQL4 DNA helicase gene, significantly increasing the risk of osteosarcoma.

Question 791

Topic: Bone Tumors
A 9-year-old girl is evaluated for a limp and a leg-length discrepancy. Physical exam notes large café-au-lait macules with irregular, "coast of Maine" borders. She also has a history of early-onset menses. Radiographs show a polyostotic intramedullary lesion with a hazy, "ground-glass" appearance. This clinical syndrome is associated with a mutation affecting which of the following?
. Tyrosine kinase receptor
. Gs alpha subunit of adenylyl cyclase
. TGF-beta receptor
. Fibroblast growth factor receptor 3
. Parathyroid hormone receptor

Correct Answer & Explanation

. Gs alpha subunit of adenylyl cyclase

Explanation

McCune-Albright syndrome consists of polyostotic fibrous dysplasia, precocious puberty, and café-au-lait spots. It is caused by a somatic activating mutation in the GNAS gene, which encodes the Gs alpha subunit of adenylyl cyclase, leading to continuous cAMP production.

Question 792

Topic: Bone Tumors

A 16-year-old boy undergoes resection of a distal femur conventional osteosarcoma.

What is the standard neoadjuvant chemotherapy regimen utilized for this malignancy?

. Vincristine, doxorubicin, and cyclophosphamide
. Methotrexate, doxorubicin, and cisplatin
. Ifosfamide and etoposide
. Imatinib mesylate
. Isolated limb perfusion with TNF-alpha

Correct Answer & Explanation

. Methotrexate, doxorubicin, and cisplatin

Explanation

The standard first-line chemotherapy regimen for conventional osteosarcoma is MAP, which stands for high-dose Methotrexate, Adriamycin (doxorubicin), and Platinol (cisplatin). This regimen is typically administered both before (neoadjuvant) and after (adjuvant) surgical resection.

Question 793

Topic: Bone Tumors

A 15-year-old girl is diagnosed with a high-grade conventional osteosarcoma of the proximal tibia. What is the most appropriate imaging modality to evaluate for the presence of skip metastases within the affected limb?

. CT scan of the lower extremity with IV contrast
. Technetium-99m bone scan
. MRI of the entire tibia and femur
. Ultrasound of the popliteal fossa
. Plain radiographs of the entire lower extremity

Correct Answer & Explanation

. MRI of the entire tibia and femur

Explanation

MRI of the entire affected bone (and adjacent joints) is the gold standard for detecting skip metastases in osteosarcoma. Finding a skip lesion upgrades the staging and alters surgical margins.

Question 794

Topic: Bone Tumors

Which of the following bone surface tumors is typically a high-grade lesion that shares the same prognosis and treatment protocol as conventional intramedullary osteosarcoma?

. Parosteal osteosarcoma
. Periosteal osteosarcoma
. High-grade surface osteosarcoma
. Osteochondroma
. Periosteal chondroma

Correct Answer & Explanation

. High-grade surface osteosarcoma

Explanation

High-grade surface osteosarcoma is the least common of the surface osteosarcomas but behaves identically to conventional intramedullary osteosarcoma. It requires neoadjuvant chemotherapy and wide resection.

Question 795

Topic: Bone Tumors

Which of the following is the radiographic hallmark required for the definitive diagnosis of an osteochondroma?

. A stippled calcification pattern within the soft tissues
. Direct continuity of the medullary canal and cortex with the underlying bone
. A solid periosteal reaction with a Codman's triangle
. Presence of a sclerotic rim surrounding a lytic nidus
. MDM2 gene amplification on fluorescent in situ hybridization

Correct Answer & Explanation

. Direct continuity of the medullary canal and cortex with the underlying bone

Explanation

The pathognomonic feature of an osteochondroma is the continuity of both the cortical bone and the medullary canal of the lesion with that of the host bone. This distinguishes it from parosteal surface lesions.

Question 796

Topic: Bone Tumors

Which of the following chemotherapy agents are considered the standard first-line neoadjuvant regimen for conventional high-grade osteosarcoma?

. Vincristine, Doxorubicin, and Cyclophosphamide
. Methotrexate, Doxorubicin, and Cisplatin
. Ifosfamide and Etoposide
. Imatinib and Sunitinib
. Paclitaxel and Carboplatin

Correct Answer & Explanation

. Methotrexate, Doxorubicin, and Cisplatin

Explanation

The standard MAP regimen for osteosarcoma consists of high-dose Methotrexate, Adriamycin (Doxorubicin), and Platin (Cisplatin). This neoadjuvant treatment is followed by wide surgical resection.

Question 797

Topic: Bone Tumors

A 28-year-old female presents with a painless, slow-growing mass behind her knee. Radiographs reveal a densely ossified, lobulated mass arising from the posterior cortex of the distal femur, separated from the underlying bone by a narrow radiolucent cleft (the "string sign"). What is the most likely diagnosis?

. Periosteal osteosarcoma
. High-grade surface osteosarcoma
. Parosteal osteosarcoma
. Myositis ossificans
. Sessile osteochondroma

Correct Answer & Explanation

. Parosteal osteosarcoma

Explanation

Parosteal osteosarcoma is a low-grade surface malignancy that most frequently arises on the posterior distal femur. It classically presents with dense, mature ossification at its base and a radiolucent cleft separating the tumor from the cortex, known as the 'string sign'.

Question 798

Topic: Bone Tumors

In a child with Hereditary Multiple Exostoses (HME), what is the most common forearm deformity requiring surgical intervention?

. Relative radial shortening with ulnar bowing
. Relative ulnar shortening with secondary radial bowing
. Proximal radioulnar synostosis
. Volar subluxation of the distal ulna
. Madelung deformity

Correct Answer & Explanation

. Relative ulnar shortening with secondary radial bowing

Explanation

The most common forearm deformity in HME (Masada type I) is caused by a distal ulnar osteochondroma tethering growth, resulting in relative ulnar shortening, secondary radial bowing, and ulnar deviation of the carpus. Without intervention, this can lead to radial head dislocation.

Question 799

Topic: Bone Tumors

Which of the following surface osteosarcoma variants is typically intermediate-grade, has a prominent chondroblastic histologic component, and classically presents as a "sunburst" periosteal reaction on the diaphyseal surface without medullary involvement?

. Parosteal osteosarcoma
. Periosteal osteosarcoma
. High-grade surface osteosarcoma
. Secondary osteosarcoma
. Telangiectatic osteosarcoma

Correct Answer & Explanation

. Periosteal osteosarcoma

Explanation

Periosteal osteosarcoma is an intermediate-grade surface tumor predominantly affecting the diaphyseal surface of long bones. It is characteristically chondroblastic, exhibits a 'sunburst' periosteal reaction, and typically lacks medullary canal invasion.

Question 800

Topic: Bone Tumors

A 10-year-old girl with hereditary multiple exostoses presents with progressive forearm deformity.

Which of the following describes the most classic pattern of forearm deformity seen in this condition?

. Ulnar shortening and radial bowing
. Radial shortening and ulnar bowing
. Proximal radioulnar synostosis
. Volar subluxation of the carpus
. Madelung deformity with positive ulnar variance

Correct Answer & Explanation

. Ulnar shortening and radial bowing

Explanation

The classic forearm deformity in HME features ulnar shortening relative to the radius, resulting in radial bowing and potential dislocation of the radial head. This occurs because osteochondromas disproportionately affect the growth of the distal ulna.

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