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Bone Tumors MCQs

Practice Set 44 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 861

Topic: Bone Tumors

In patients with Multiple Hereditary Exostoses (MHE), the characteristic forearm deformity is primarily driven by osteochondromas affecting which specific location, leading to the classic tethering effect?

. Proximal radius
. Distal radius
. Proximal ulna
. Distal ulna
. Diaphysis of the radius

Correct Answer & Explanation

. Distal ulna

Explanation

Correct Answer: D (Distal ulna)The classic forearm deformity in Multiple Hereditary Exostoses (MHE) is primarily caused by the disproportionate involvement of the distal ulna. The distal ulna has a smaller cross-sectional area and contributes a larger percentage to the overall longitudinal growth of the ulna compared to the radius. Osteochondromas here cause significant growth retardation of the ulna, leading to relative ulnar shortening, secondary bowing of the radius, ulnar deviation of the carpus, and potential radial head dislocation.

Question 862

Topic: Bone Tumors

A 12-year-old boy with polyostotic fibrous dysplasia presents with a progressive 'shepherd's crook' deformity of the proximal femur. Surgical correction is planned. Which of the following principles is most critical for the successful long-term stabilization of this deformity?

. Use of non-vascularized cortical strut allografts
. Curettage and packing with cancellous autograft
. Stabilization with a load-sharing intramedullary device
. Stabilization with a rigid laterally based plate and screws
. Wide resection and endoprosthetic reconstruction

Correct Answer & Explanation

. Stabilization with a load-sharing intramedullary device

Explanation

Correct Answer: C (Stabilization with a load-sharing intramedullary device)In fibrous dysplasia, the abnormal bone is structurally weak. Bone grafting (both autograft and allograft) typically fails because the graft is resorbed and replaced by dysplastic host bone. Rigid plate fixation also has a high failure rate due to poor screw purchase in the dysplastic bone and stress shielding. The gold standard for stabilizing a corrected 'shepherd's crook' deformity is the use of load-sharing intramedullary devices (like a cephalomedullary nail), which span the entire length of the abnormal bone and protect it from bending forces.

Question 863

Topic: Bone Tumors
A 6-year-old girl is evaluated for a limp and a leg-length discrepancy. Radiographs reveal expansile, ground-glass lesions in her left femur and tibia. Physical examination notes large, hyperpigmented skin macules with irregular borders on her torso. Which of the following endocrine abnormalities is most commonly associated with her likely diagnosis?
. Hypothyroidism
. Precocious puberty
. Hyperparathyroidism
. Diabetes insipidus
. Adrenal insufficiency

Correct Answer & Explanation

. Precocious puberty

Explanation

The patient's presentation of polyostotic fibrous dysplasia and café-au-lait spots with irregular ('coast of Maine') borders is diagnostic of McCune-Albright syndrome. This syndrome is caused by a post-zygotic somatic mutation in the GNAS gene, leading to overactivation of adenylyl cyclase. The most common endocrine abnormality associated with McCune-Albright syndrome is gonadotropin-independent precocious puberty, particularly in females.

Question 864

Topic: Bone Tumors

A 12-year-old girl presents with a pathologic fracture of the proximal femur. Radiographs show a 'ground-glass' appearance in the medullary canal with a shepherd's crook deformity. Which of the following genetic mutations is most likely responsible for the underlying condition?

. FGFR3 mutation
. COMP mutation
. GNAS1 mutation
. EXT1 mutation

Correct Answer & Explanation

. GNAS1 mutation

Explanation

Correct Answer: GNAS1 mutationThe clinical and radiographic presentation is classic for fibrous dysplasia. Fibrous dysplasia is caused by a somatic, activating mutation in the GNAS1 gene, which encodes the alpha subunit of the stimulatory G protein (Gs-alpha). This leads to increased intracellular cAMP levels, resulting in abnormal proliferation and differentiation of osteoblasts, replacing normal bone with fibrous stroma and woven bone. FGFR3 mutations are seen in achondroplasia, COMP in pseudoachondroplasia, and EXT1 in multiple hereditary exostoses.

Question 865

Topic: Bone Tumors

A 10-year-old boy presents with multiple bony prominences around his knees and ankles, causing a valgus deformity at the knees. Family history is positive for similar lesions. The pathogenesis of this condition involves a defect in which of the following?

. Type I collagen synthesis
. Heparan sulfate glycosaminoglycan synthesis
. Fibroblast growth factor receptor 3 signaling
. G-protein coupled receptor signaling

Correct Answer & Explanation

. Heparan sulfate glycosaminoglycan synthesis

Explanation

Correct Answer: Heparan sulfate glycosaminoglycan synthesisThe patient has Multiple Hereditary Exostoses (MHE), also known as diaphyseal aclasis. MHE is an autosomal dominant condition caused by mutations in the EXT1 or EXT2 genes. These genes encode glycosyltransferases that are essential for the synthesis of heparan sulfate, a glycosaminoglycan. The deficiency in heparan sulfate disrupts normal Indian hedgehog (Ihh) signaling in the growth plate, leading to the formation of osteochondromas.

Question 866

Topic: Bone Tumors
An asymptomatic 25-year-old man undergoes a routine pelvic radiograph following a minor trauma. The radiograph incidentally shows numerous small, well-defined, symmetric, periarticular sclerotic foci in the pelvis and proximal femurs. If this patient has an associated skin condition, what is the most likely dermatological finding?
. Café-au-lait spots
. Dermatofibrosis lenticularis disseminata
. Port-wine stains
. Subcutaneous hemangiomas

Correct Answer & Explanation

. Dermatofibrosis lenticularis disseminata

Explanation

The radiographic findings are classic for osteopoikilosis ('spotted bone disease'), an autosomal dominant sclerosing dysplasia caused by LEMD3 mutations. When osteopoikilosis is associated with connective tissue nevi (specifically dermatofibrosis lenticularis disseminata), the condition is known as Buschke-Ollendorff syndrome. Café-au-lait spots are seen in neurofibromatosis and McCune-Albright syndrome. Hemangiomas are seen in Maffucci syndrome.

Question 867

Topic: Bone Tumors

A 14-year-old boy with polyostotic fibrous dysplasia presents with progressive varus bowing of the proximal femur (shepherd's crook deformity) and increasing thigh pain. What is the most appropriate surgical management for this deformity?

. Curettage and packing with cancellous autograft
. Curettage and packing with cortical allograft
. Valgus producing osteotomy and intramedullary nailing
. Valgus producing osteotomy and plate fixation

Correct Answer & Explanation

. Valgus producing osteotomy and intramedullary nailing

Explanation

Correct Answer: Valgus producing osteotomy and intramedullary nailingIn fibrous dysplasia, the entire bone is often mechanically compromised. Bone grafts (especially cancellous) are typically resorbed and replaced by dysplastic host bone, leading to high failure rates. Plate fixation is also prone to failure due to poor screw purchase in the dysplastic bone and the stress-shielding effect. The gold standard for correcting a shepherd's crook deformity is a valgus-producing osteotomy stabilized with a load-sharing intramedullary device (nail) that spans the entire length of the abnormal bone.

Question 868

Topic: Bone Tumors

A 10-year-old girl is evaluated for mild developmental delay and macrocephaly. Radiographs of her lower extremities reveal multiple, parallel, linear bands of sclerosis extending from the metaphyses into the diaphyses of the long bones. Which of the following is the most likely diagnosis?

. Osteopetrosis
. Osteopoikilosis
. Osteopathia striata
. Melorheostosis

Correct Answer & Explanation

. Osteopoikilosis

Explanation

Correct Answer: Osteopathia striataOsteopathia striata (Voorhoeve disease) is a rare sclerosing bone dysplasia characterized radiographically by linear, parallel striations of dense bone in the metaphyses and diaphyses of long bones, and a sunburst appearance in the ilium. It can occur isolated or as part of osteopathia striata with cranial sclerosis (OSCS), an X-linked dominant condition caused by WTX gene mutations, which presents with macrocephaly, cleft palate, and developmental delay.

Question 869

Topic: Bone Tumors
A 7-year-old girl presents with a history of early breast development and vaginal bleeding. Physical examination reveals large, irregular café-au-lait macules with 'coast of Maine' borders on her trunk. Radiographs show expansile, ground-glass lesions in her left femur and tibia. Which of the following endocrine abnormalities is most commonly associated with this patient's syndrome?
. Hypothyroidism
. Precocious puberty
. Hypoparathyroidism
. Diabetes mellitus

Correct Answer & Explanation

. Precocious puberty

Explanation

The patient has McCune-Albright syndrome, a classic triad of polyostotic fibrous dysplasia, café-au-lait spots (with irregular 'coast of Maine' borders), and endocrine hyperfunction. The most common endocrine abnormality is gonadotropin-independent precocious puberty, especially in females. Other possible endocrine issues include hyperthyroidism, growth hormone excess, and Cushing syndrome.

Question 870

Topic: Bone Tumors

A 15-year-old boy with polyostotic fibrous dysplasia presents with a progressive "shepherd's crook" deformity of the proximal femur and mechanical hip pain. Which surgical construct is most appropriate for stabilizing the femur following corrective osteotomy?

. Non-vascularized fibular strut graft
. Cancellous bone grafting and a dynamic hip screw
. Intramedullary nailing
. External fixation
. Cortical onlay grafting alone

Correct Answer & Explanation

. Intramedullary nailing

Explanation

In fibrous dysplasia, the weak fibro-osseous tissue makes extramedullary plates prone to failure due to poor screw purchase. Intramedullary nailing is the preferred fixation method as it protects the entire length of the bone and effectively unloads the dysplastic cortex.

Question 871

Topic: Bone Tumors

A 15-year-old boy with polyostotic fibrous dysplasia presents with a progressing proximal femur deformity.

Surgical management is planned to restore mechanical alignment. Which of the following is the most appropriate biomechanical approach for reconstruction?

. Cortical onlay allografting with rigid plate fixation
. Curettage, cancellous bone grafting, and dynamic hip screw placement
. Intramedullary nailing utilizing cortical strut grafts
. External fixation for gradual deformity correction
. Resection and megaprosthesis reconstruction

Correct Answer & Explanation

. Intramedullary nailing utilizing cortical strut grafts

Explanation

In fibrous dysplasia, load-sharing intramedullary devices are essential because plates often fail due to the poor quality of the surrounding bone. Additionally, cortical bone grafts are preferred because cancellous grafts are rapidly resorbed and replaced by dysplastic tissue.

Question 872

Topic: Bone Tumors

Which histological feature helps differentiate primary synovial chondromatosis from secondary synovial chondromatosis?

. Presence of bone formation within the nodules
. Cellular atypia, hypercellularity, and binucleated chondrocytes
. Extensive acute inflammatory infiltrates
. Concentric rings of ossification without atypia
. Abundant multinucleated giant cells

Correct Answer & Explanation

. Cellular atypia, hypercellularity, and binucleated chondrocytes

Explanation

Primary synovial chondromatosis often exhibits hypercellularity, cellular atypia, pleomorphism, and binucleated chondrocytes, which can easily mimic a low-grade chondrosarcoma. Secondary chondromatosis typically shows mature cartilage with rings of ossification and lacks significant atypia.

Question 873

Topic: Bone Tumors
A 9-year-old girl presents with a limp and a shepherd's crook deformity of the proximal femur. She also has large, irregularly bordered hyperpigmented skin macules. What endocrine abnormality is most commonly associated with this syndrome?
. Hypothyroidism
. Precocious puberty
. Hyperparathyroidism
. Adrenal insufficiency
. Diabetes insipidus

Correct Answer & Explanation

. Precocious puberty

Explanation

The presentation describes McCune-Albright syndrome, which consists of polyostotic fibrous dysplasia, café-au-lait spots (Coast of Maine borders), and hyperfunctioning endocrinopathies. Precocious puberty is the most common endocrine manifestation.

Question 874

Topic: Bone Tumors

A routine radiograph of a 25-year-old patient reveals an expansile, intramedullary lesion in the proximal femur with a hazy, 'ground-glass' appearance and endosteal scalloping. What is the recommended surgical management if the lesion is completely asymptomatic and structurally stable?

. Curettage and bone grafting with allograft
. Prophylactic intramedullary nailing
. En bloc resection and endoprosthetic reconstruction
. Observation with serial radiographs
. Intralesional corticosteroid injection

Correct Answer & Explanation

. Observation with serial radiographs

Explanation

Asymptomatic, structurally stable fibrous dysplasia lesions are typically managed with observation. Curettage and grafting generally fail because the graft is resorbed and rapidly replaced by dysplastic host tissue.

Question 875

Topic: Bone Tumors

A 22-year-old male with polyostotic fibrous dysplasia presents with a severe Shepherd's crook deformity of the proximal femur.

When planning corrective osteotomy and fixation, which biomechanical principle is most critical to prevent mechanical failure?

. Use of a sliding hip screw with extensive cancellous bone graft
. Use of a load-sharing intramedullary device spanning the entire femur
. Curettage and isolated cortical strut allografting
. Total hip arthroplasty using a cemented stem
. External fixation with progressive distraction osteogenesis

Correct Answer & Explanation

. Use of a load-sharing intramedullary device spanning the entire femur

Explanation

In the surgical treatment of fibrous dysplasia deformities (like Shepherd's crook), intramedullary nailing spanning the entire length of the bone is required. Plates and screws have an unacceptably high failure rate because the abnormal host bone cannot adequately hold screws or share loads.

Question 876

Topic: Bone Tumors

A 9-year-old girl presents with a limp and a history of early-onset puberty. Radiographs reveal multiple expansile ground-glass lesions in the femur and tibia. Physical exam notes large, irregular hyperpigmented skin macules. What is the classic term for these skin lesions?

. Coast of California spots
. Coast of Maine spots
. Ash-leaf spots
. Shagreen patches
. Lisch nodules

Correct Answer & Explanation

. Coast of Maine spots

Explanation

The patient has McCune-Albright syndrome, characterized by the triad of polyostotic fibrous dysplasia, precocious puberty, and cafe-au-lait spots. The cafe-au-lait spots in this syndrome have irregular borders, classically described as the 'Coast of Maine', unlike the smooth 'Coast of California' spots seen in neurofibromatosis.

Question 877

Topic: Bone Tumors

A 25-year-old patient with polyostotic fibrous dysplasia presents with increasing hip pain and a progressive varus deformity of the proximal femur. What is the most appropriate surgical management for this characteristic "shepherd's crook" deformity?

. Curettage and bone grafting with cancellous allograft
. Valgus-producing osteotomy and load-sharing intramedullary nail fixation
. Total hip arthroplasty
. Proximal femoral resection and endoprosthetic reconstruction
. Observation and intravenous bisphosphonate therapy

Correct Answer & Explanation

. Valgus-producing osteotomy and load-sharing intramedullary nail fixation

Explanation

The shepherd's crook deformity in fibrous dysplasia requires correction of the mechanical axis via a valgus osteotomy, followed by load-sharing intramedullary fixation to bypass the entire abnormal bone segment. Cancellous bone grafts should be avoided as they resorb and are rapidly replaced by dysplastic host bone.

Question 878

Topic: Bone Tumors

A 25-year-old woman with known fibrous dysplasia presents with increasing thigh pain and a progressive shepherd's crook deformity. What is the most appropriate surgical management to address her symptoms and deformity?

. Curettage and autologous cancellous bone grafting
. Valgus osteotomy and rigid plate fixation
. Valgus osteotomy and intramedullary nailing
. Intravenous bisphosphonate therapy alone
. En bloc resection and endoprosthetic reconstruction

Correct Answer & Explanation

. Valgus osteotomy and intramedullary nailing

Explanation

Surgical management of a shepherd's crook deformity involves valgus producing osteotomies stabilized with intramedullary nailing. Plate fixation is prone to failure due to the poor quality of dysplastic bone, and cancellous bone grafts are rapidly resorbed.

Question 879

Topic: Bone Tumors

A 35-year-old female is diagnosed with polyostotic fibrous dysplasia. During her workup, an MRI of her thigh unexpectedly reveals multiple well-circumscribed, T2-hyperintense soft tissue masses within her skeletal muscle. What is the correct diagnosis for this presentation?

. McCune-Albright syndrome
. Mazabraud syndrome
. Jaffe-Campanacci syndrome
. Ollier disease
. Maffucci syndrome

Correct Answer & Explanation

. Mazabraud syndrome

Explanation

Mazabraud syndrome is the rare combination of polyostotic fibrous dysplasia and multiple intramuscular myxomas. The myxomas are typically benign and appear hyperintense on T2-weighted MRI.

Question 880

Topic: Bone Tumors

Which classic histologic feature clearly distinguishes fibrous dysplasia from normal bone and other reactive fibro-osseous lesions?

. Prominent osteoblastic rimming of thickened trabeculae
. Irregular woven bone trabeculae lacking osteoblastic rimming
. Presence of multinucleated giant cells in a hemorrhagic background
. Nests of atypical chondrocytes with binucleation
. Sheets of plasma cells with eccentric nuclei

Correct Answer & Explanation

. Irregular woven bone trabeculae lacking osteoblastic rimming

Explanation

Fibrous dysplasia is histologically characterized by irregular, "Chinese character" shaped trabeculae of woven bone that arise directly from a fibrous stroma without normal osteoblastic rimming.

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