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Bone Tumors MCQs

Practice Set 45 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 881

Topic: Bone Tumors

A 24-year-old with polyostotic fibrous dysplasia presents with a progressively painful Shepherd's crook deformity of the proximal femur.

If surgical intervention is elected to correct the deformity and prevent fracture, which of the following is the most appropriate biomechanical and biological strategy?

. Valgus osteotomy with cancellous bone grafting and plate fixation
. Intramedullary nailing with or without cortical bone grafting
. Curettage and cementation with prophylactic plate fixation
. Resection and endoprosthetic reconstruction
. Observation and initiation of denosumab therapy

Correct Answer & Explanation

. Intramedullary nailing with or without cortical bone grafting

Explanation

Fibrous dysplasia replaces normal bone with weak woven bone. Cancellous bone grafts are consistently resorbed by the host dysplastic tissue, so cortical allografts or intramedullary devices spanning the entire bone are required for durable fixation.

Question 882

Topic: Bone Tumors
A 9-year-old girl is evaluated for precocious puberty and café-au-lait spots with irregular "coast of Maine" borders. Radiographs of her lower extremities demonstrate multiple lucent, ground-glass bone lesions. Which of the following best describes the underlying genetic anomaly in this patient?
. Germline mutation in the EXT1 gene
. Post-zygotic somatic mutation of the GNAS gene
. Germline mutation of the GNAS gene
. Defect in the COL1A1 gene
. Mutation in the FGFR3 gene

Correct Answer & Explanation

. Post-zygotic somatic mutation of the GNAS gene

Explanation

This patient presents with McCune-Albright syndrome (polyostotic fibrous dysplasia, endocrinopathy, café-au-lait spots). It is caused by a post-zygotic somatic missense mutation in the GNAS gene; a germline mutation of this gene is lethal.

Question 883

Topic: Bone Tumors

A 14-year-old girl with a history of precocious puberty and large cafe-au-lait spots presents with a pathologic fracture of her proximal femur. Radiographs show a ground-glass lytic lesion with a shepherd's crook deformity. What is the underlying genetic mutation?

. GNAS1
. EXT1
. NF1
. FGFR3
. SH3BP2

Correct Answer & Explanation

. GNAS1

Explanation

McCune-Albright syndrome consists of polyostotic fibrous dysplasia, cafe-au-lait spots (with irregular 'coast of Maine' borders), and endocrine abnormalities. It is caused by a post-zygotic somatic activating mutation in the GNAS1 gene.

Question 884

Topic: Bone Tumors

Which of the following magnetic resonance imaging (MRI) findings is most characteristic of an aneurysmal bone cyst?

. A uniform target sign on T2-weighted images
. Fluid-fluid levels on T2-weighted images
. A radiolucent nidus with surrounding dense sclerosis
. Popcorn calcification in the medullary canal
. A uniform ground-glass appearance

Correct Answer & Explanation

. Fluid-fluid levels on T2-weighted images

Explanation

Fluid-fluid levels on T2-weighted MRI are the hallmark of an aneurysmal bone cyst. This phenomenon occurs due to the separation of serum and red blood cells within the cystic spaces.

Question 885

Topic: Bone Tumors
An 8-year-old female is evaluated for multiple bony deformities, irregular café-au-lait spots, and early onset of menses. Which of the following gene mutations is responsible for her condition?
. NF1
. COL1A1
. GNAS1
. EXT1
. FGFR3

Correct Answer & Explanation

. GNAS1

Explanation

This patient has McCune-Albright syndrome, a polyostotic form of fibrous dysplasia associated with endocrine abnormalities and coast of Maine café-au-lait spots. It is caused by an activating post-zygotic mutation in the GNAS1 gene, increasing cAMP levels.

Question 886

Topic: Bone Tumors

A 25-year-old with polyostotic fibrous dysplasia undergoes surgical correction of a shepherd's crook deformity. If bone grafting is necessary, which of the following materials is relatively contraindicated due to its tendency to be rapidly resorbed?

. Cancellous autograft
. Cortical allograft
. Vascularized fibular graft
. Structural allograft strut
. Synthetic calcium phosphate

Correct Answer & Explanation

. Cortical allograft

Explanation

Cancellous autograft is contraindicated in fibrous dysplasia because it is rapidly resorbed and replaced by dysplastic host tissue. Cortical allograft is preferred as it undergoes slow creeping substitution, providing prolonged structural support.

Question 887

Topic: Bone Tumors

When planning surgical fixation for an impending proximal femur fracture in a patient with a shepherd's crook deformity from fibrous dysplasia, which of the following implants provides the most reliable long-term outcome?

. Dynamic hip screw with a side plate
. Cephalomedullary nail
. Proximal femoral locking plate
. External fixator
. Hemiarthroplasty

Correct Answer & Explanation

. Cephalomedullary nail

Explanation

Intramedullary devices, such as a cephalomedullary nail, are the implants of choice for fibrous dysplasia in the lower extremity. Plates and screws have an unacceptably high failure rate due to poor screw purchase in the dysplastic bone.

Question 888

Topic: Bone Tumors

What is considered the gold standard surgical treatment to minimize recurrence for an aggressive aneurysmal bone cyst of the proximal tibia in a 16-year-old?

. En bloc wide resection
. Intralesional curettage alone
. Extended curettage with high-speed burring and adjuvant therapy
. Primary sclerotherapy
. Amputation

Correct Answer & Explanation

. Extended curettage with high-speed burring and adjuvant therapy

Explanation

Extended curettage with a high-speed burr and the use of chemical or physical adjuvants (e.g., phenol, argon beam, cryotherapy) is the gold standard for ABCs. This aggressive local treatment significantly lowers the recurrence rate compared to simple curettage.

Question 889

Topic: Bone Tumors

Which of the following is the histological hallmark of fibrous dysplasia?

. Endothelial-lined blood spaces separated by fibrous septa
. Chondroid matrix with a "chicken wire" calcification pattern
. Irregular trabeculae of woven bone lacking osteoblastic rimming in a fibrous stroma
. Sheets of small round blue cells with scant cytoplasm
. Abundant multinucleated giant cells in a sea of mononuclear cells

Correct Answer & Explanation

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

Explanation

The classic histological finding of fibrous dysplasia is irregular, C- or W-shaped trabeculae of woven bone ("Chinese characters") arising directly from a fibrous stroma. Crucially, these bone trabeculae lack functional osteoblastic rimming.

Question 890

Topic: Bone Tumors

Which endocrinopathy is the most common and classic manifestation associated with McCune-Albright syndrome?

. Hypothyroidism
. Central diabetes insipidus
. Precocious puberty
. Primary adrenal insufficiency
. Hyperparathyroidism

Correct Answer & Explanation

. Precocious puberty

Explanation

Peripheral precocious puberty is the most common endocrine abnormality in McCune-Albright syndrome, particularly in females. It results from autonomous, gonadotropin-independent ovarian estrogen production driven by the GNAS mutation.

Question 891

Topic: Bone Tumors

Which of the following radiographic features best differentiates an aneurysmal bone cyst (ABC) from a unicameral bone cyst (UBC) in a long bone?

. An ABC is typically centrally located within the medullary canal.
. An ABC is typically eccentric and expansile, often blowing out the cortex.
. A UBC frequently crosses the open physis into the epiphysis.
. A UBC demonstrates diagnostic fluid-fluid levels on MRI.
. An ABC consistently resolves spontaneously with skeletal maturity.

Correct Answer & Explanation

. An ABC is typically eccentric and expansile, often blowing out the cortex.

Explanation

Radiographically, an ABC is an eccentric, expansile, lytic lesion that may thin or "blow out" the cortex. In contrast, a UBC is typically centrally located within the metaphysis or diaphysis and rarely expands beyond the normal width of the physis.

Question 892

Topic: Bone Tumors

A 12-year-old boy presents with knee pain and swelling. Radiographs show an eccentric, expansile lytic lesion in the distal femoral metaphysis. MRI demonstrates multiple fluid-fluid levels. Genetic analysis of the tissue is most likely to reveal which of the following translocations?

. t(11;22)
. t(X;18)
. t(12;16)
. t(16;17)
. t(2;13)

Correct Answer & Explanation

. t(16;17)

Explanation

The diagnosis is an aneurysmal bone cyst (ABC). Primary ABCs are neoplasms driven by a specific t(16;17) translocation that upregulates the USP6 gene.

Question 893

Topic: Bone Tumors

A 25-year-old female presents with a progressive bowing deformity of her proximal femur. Radiographs display a "ground-glass" appearance in the medullary canal with a "Shepherd's crook" deformity. A mutation in which of the following genes is responsible for this condition?

. EXT1
. GNAS
. FGFR3
. COL1A1
. RUNX2

Correct Answer & Explanation

. GNAS

Explanation

The patient has fibrous dysplasia, caused by a post-zygotic, activating missense mutation in the GNAS gene. This leads to constitutive activation of the Gs-alpha protein and increased intracellular cAMP, disrupting normal osteoblast differentiation.

Question 894

Topic: Bone Tumors
A 9-year-old girl is diagnosed with polyostotic fibrous dysplasia. Physical examination reveals a large hyperpigmented macule on her back with irregular borders. Which of the following endocrine abnormalities is most commonly associated with her underlying syndrome?
. Hyperthyroidism
. Acromegaly
. Precocious puberty
. Cushing syndrome
. Hyperparathyroidism

Correct Answer & Explanation

. Precocious puberty

Explanation

The patient has McCune-Albright syndrome (polyostotic fibrous dysplasia, "coast of Maine" café-au-lait spots, and endocrinopathies). Precocious puberty is the most common endocrine manifestation of this syndrome.

Question 895

Topic: Bone Tumors

A radiologist describes a benign-appearing, expansile, diaphyseal radiolucent lesion with a "rind" of reactive sclerosis on the radiograph of a 30-year-old. This typical "rind" sign is most pathognomonic for which of the following conditions?

. Non-ossifying fibroma
. Chondromyxoid fibroma
. Fibrous dysplasia
. Aneurysmal bone cyst
. Simple bone cyst

Correct Answer & Explanation

. Fibrous dysplasia

Explanation

Fibrous dysplasia lesions are typically diaphyseal or metadiaphyseal, exhibiting a "ground-glass" matrix and often surrounded by a thick, sclerotic rim of reactive bone known as the "rind" sign.

Question 896

Topic: Bone Tumors

An 8-year-old girl is diagnosed with polyostotic fibrous dysplasia. She has large cafe-au-lait spots with irregular borders on her trunk. Which of the following endocrine abnormalities is most commonly associated with her condition?

. Hypothyroidism
. Diabetes mellitus
. Precocious puberty
. Hypoparathyroidism
. Adrenal insufficiency

Correct Answer & Explanation

. Precocious puberty

Explanation

McCune-Albright syndrome consists of polyostotic fibrous dysplasia, cafe-au-lait spots with coast of Maine borders, and endocrinopathies. The most common endocrine manifestation is precocious puberty.

Question 897

Topic: Bone Tumors

Which of the following surgical techniques is considered the gold standard for managing a symptomatic shepherd's crook deformity in a patient with polyostotic fibrous dysplasia?

. Curettage and bone grafting with cancellous allograft
. Valgus producing osteotomy stabilized with a plate and screws
. Valgus producing osteotomy stabilized with an intramedullary nail
. Resection and endoprosthetic reconstruction
. Radiation therapy followed by casting

Correct Answer & Explanation

. Valgus producing osteotomy stabilized with an intramedullary nail

Explanation

Cortical bone replacement via intramedullary nailing combined with a valgus osteotomy is the most reliable treatment for a shepherd's crook deformity. Plating has a high failure rate, and bone grafts tend to resorb.

Question 898

Topic: Bone Tumors

Histopathological examination of a proximal femoral lesion demonstrates woven bone trabeculae in a fibrous stroma without osteoblastic rimming. What radiographic feature is most characteristic of this condition?

. Sunburst periosteal reaction
. Epiphyseal location crossing the physis
. Well-circumscribed intramedullary lesion with a ground-glass matrix
. Soap-bubble appearance with cortical breakthrough
. Popcorn calcifications

Correct Answer & Explanation

. Well-circumscribed intramedullary lesion with a ground-glass matrix

Explanation

The histology is pathognomonic for fibrous dysplasia, displaying Chinese character trabeculae. The classic radiographic finding is a well-circumscribed medullary lesion with a ground-glass appearance.

Question 899

Topic: Bone Tumors

An 11-year-old boy undergoes extended intralesional curettage of an aneurysmal bone cyst in the distal tibia. Which of the following is most commonly used during this procedure to reduce the rate of local recurrence?

. Hydrogen peroxide
. High-speed burr and phenol
. Chlorhexidine irrigation
. Intravenous antibiotics
. Methotrexate wash

Correct Answer & Explanation

. High-speed burr and phenol

Explanation

Treatment of ABCs involves extended intralesional curettage, mechanical burring, and chemical or thermal adjuvants like phenol or liquid nitrogen. This multimodal approach effectively kills remaining cyst cells to prevent recurrence.

Question 900

Topic: Bone Tumors

A 21-year-old female presents with recurrent swelling of her proximal humerus 18 months after curettage of an Aneurysmal Bone Cyst. Which of the following surgical factors is most strongly associated with an increased risk of ABC recurrence?

. Older patient age
. Presence of a USP6 translocation
. Incomplete surgical removal without high-speed burring
. Use of phenol as an adjuvant
. Diaphyseal location

Correct Answer & Explanation

. Incomplete surgical removal without high-speed burring

Explanation

The most significant risk factor for the recurrence of an aneurysmal bone cyst is incomplete intralesional excision. Adding mechanical adjuvants like a high-speed burr significantly decreases the recurrence rate.

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