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Bone Tumors MCQs

Practice Set 52 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 1021

Topic: Bone Tumors

A 12-year-old boy with polyostotic fibrous dysplasia requires surgical intervention for a progressive 'shepherd's crook' deformity of the proximal femur. Which of the following surgical strategies is most appropriate to prevent recurrence and achieve stable fixation?

. Curettage and packing with autologous cancellous bone graft
. Valgus osteotomy stabilized with a dynamic hip screw and side plate
. Valgus osteotomy stabilized with an intramedullary nail
. Resection of the dysplastic bone and replacement with a massive allograft
. Curettage and packing with cortical strut allografts

Correct Answer & Explanation

. Valgus osteotomy stabilized with an intramedullary nail

Explanation

Correct Answer: Valgus osteotomy stabilized with an intramedullary nailSurgical management of the shepherd's crook deformity in fibrous dysplasia is challenging due to poor bone quality. Cortical and cancellous bone grafts (both auto- and allografts) typically resorb and are replaced by dysplastic bone, leading to recurrence. Plate and screw constructs frequently fail because the dysplastic bone cannot hold screws securely. The gold standard treatment is a valgus producing osteotomy to correct the mechanical axis, stabilized with an intramedullary device (like a cephalomedullary nail) that spans the entire length of the affected bone to provide load-sharing support and prevent future fractures.

Question 1022

Topic: Bone Tumors

A 28-year-old asymptomatic woman undergoes a pelvic radiograph following a minor fall. The radiograph reveals numerous small, well-defined, symmetric sclerotic foci clustered around the periarticular regions of the pelvis and proximal femora. If this patient has an associated skin condition, what is the most likely diagnosis?

. McCune-Albright syndrome
. Mazabraud syndrome
. Buschke-Ollendorff syndrome
. Maffucci syndrome
. Neurofibromatosis type 1

Correct Answer & Explanation

. Buschke-Ollendorff syndrome

Explanation

Correct Answer: Buschke-Ollendorff syndromeThe radiographic findings describe osteopoikilosis ('spotted bone disease'), an asymptomatic, autosomal dominant sclerosing bone dysplasia characterized by numerous small, dense bone islands clustered near the ends of long bones and in the pelvis. When osteopoikilosis is associated with connective tissue nevi of the skin (disseminated lenticularis or dermatofibrosis lenticularis disseminata), the condition is known as Buschke-Ollendorff syndrome. It is associated with mutations in the LEMD3 gene.

Question 1023

Topic: Bone Tumors
A 14-year-old girl presents with a progressive 'shepherd's crook' deformity of the proximal femur and large café-au-lait spots with irregular 'coast of Maine' borders. Which of the following genetic mutations is most likely responsible for the anarchic development of bone constituents in this patient?
. Activating mutation in the GNAS1 gene
. Loss-of-function mutation in the EXT1 gene
. Gain-of-function mutation in the FGFR3 gene
. Mutation in the COMP (Cartilage Oligomeric Matrix Protein) gene
. Mutation in the COL1A1 gene

Correct Answer & Explanation

. Activating mutation in the GNAS1 gene

Explanation

This patient presents with McCune-Albright syndrome, characterized by polyostotic fibrous dysplasia, café-au-lait spots with irregular borders, and endocrine abnormalities (such as precocious puberty). Fibrous dysplasia is a classic example of anarchic bone development caused by a somatic, activating mutation in the GNAS1 gene. This mutation leads to increased intracellular cAMP, resulting in the replacement of normal bone and marrow with fibrous tissue and woven bone. EXT1 is associated with multiple hereditary exostoses, FGFR3 with achondroplasia, COMP with pseudoachondroplasia, and COL1A1 with osteogenesis imperfecta.

Question 1024

Topic: Bone Tumors

Which of the following radiographic descriptions is the classic hallmark of fibrous dysplasia?

. 'Erlenmeyer flask' deformity of the distal femur
. 'Ground-glass' appearance with a well-defined sclerotic margin
. 'Sunburst' periosteal reaction with Codman's triangle
. 'Blade of grass' or 'flame-shaped' lucency in the diaphysis
. 'Picture frame' vertebral bodies

Correct Answer & Explanation

. 'Ground-glass' appearance with a well-defined sclerotic margin

Explanation

Correct Answer: 'Ground-glass' appearance with a well-defined sclerotic marginThe classic radiographic hallmark of fibrous dysplasia is a radiolucent, 'ground-glass' appearance. This occurs because the normal trabecular bone is replaced by a homogeneous, gritty fibrous tissue containing microscopic spicules of woven bone, which scatters x-rays to create the hazy, ground-glass look. The lesions are typically intramedullary, expansile, and surrounded by a thick sclerotic rim (rind). 'Erlenmeyer flask' deformity is seen in Gaucher disease and osteopetrosis; 'Sunburst' is classic for osteosarcoma; 'Blade of grass' and 'Picture frame' vertebrae are seen in Paget's disease.

Question 1025

Topic: Bone Tumors

An incidental radiographic finding in a 40-year-old woman shows numerous small, well-defined, symmetric sclerotic foci clustered around the periarticular regions of her long bones, pelvis, and carpal bones. She is completely asymptomatic. If this patient has an associated skin condition, what is the most likely diagnosis?

. McCune-Albright syndrome
. Buschke-Ollendorff syndrome
. Mazabraud syndrome
. Neurofibromatosis type 1
. Tuberous sclerosis

Correct Answer & Explanation

. Buschke-Ollendorff syndrome

Explanation

Correct Answer: Buschke-Ollendorff syndromeThe radiographic findings describe osteopoikilosis ('spotted bone disease'), an asymptomatic, autosomal dominant sclerosing dysplasia. When osteopoikilosis is associated with disseminated connective tissue nevi (skin lesions), the condition is known as Buschke-Ollendorff syndrome. Both isolated osteopoikilosis and Buschke-Ollendorff syndrome are associated with loss-of-function mutations in the LEMD3 gene.

Question 1026

Topic: Bone Tumors
A 12-year-old girl presents with a progressive shepherd's crook deformity of the proximal femur and café-au-lait spots with irregular 'coast of Maine' borders. The underlying pathophysiology of her bone lesions is most directly related to a somatic mutation affecting which of the following?
. Fibroblast growth factor receptor 3 (FGFR3)
. Gs alpha protein (GNAS)
. Exostosin-1 (EXT1)
. Isocitrate dehydrogenase 1 (IDH1)
. Cartilage oligomeric matrix protein (COMP)

Correct Answer & Explanation

. Gs alpha protein (GNAS)

Explanation

This patient presents with McCune-Albright syndrome, a severe form of polyostotic fibrous dysplasia associated with café-au-lait spots (irregular borders) and endocrinopathies (e.g., precocious puberty). The condition is caused by a somatic, post-zygotic activating mutation in the GNAS gene. This mutation leads to constitutive activation of the Gs alpha protein, resulting in increased intracellular cAMP levels. This overactivity disrupts normal osteoblast differentiation, leading to the replacement of normal bone with fibrous tissue and immature woven bone. FGFR3 mutations are seen in achondroplasia. EXT1 mutations cause multiple hereditary exostoses. IDH1/2 mutations are associated with Ollier disease and Maffucci syndrome. COMP mutations are seen in pseudoachondroplasia and multiple epiphyseal dysplasia.

Question 1027

Topic: Bone Tumors

A 10-year-old boy with multiple hereditary exostoses presents with a progressive forearm deformity. Radiographs reveal relative shortening of the ulna, bowing of the radius, and ulnar deviation of the carpus. What is the primary biomechanical cause of this specific forearm deformity?

. Premature closure of the distal radial physis.
. Disproportionate tethering effect due to an osteochondroma at the distal ulnar physis.
. Laxity of the distal radioulnar joint ligaments.
. Overgrowth of the radial head.
. Avascular necrosis of the lunate.

Correct Answer & Explanation

. Disproportionate tethering effect due to an osteochondroma at the distal ulnar physis.

Explanation

Correct Answer: Disproportionate tethering effect due to an osteochondroma at the distal ulnar physis.In Multiple Hereditary Exostoses (MHE), forearm deformities are common and typically present as a Madelung-like deformity. The primary driver is the presence of osteochondromas at the distal ulnar physis. Because the distal ulna contributes a large percentage of the bone's overall longitudinal growth and has a smaller cross-sectional area than the radius, it is disproportionately affected by the tethering effect of the osteochondroma. This leads to ulnar shortening. The continued growth of the radius against the tethered ulna results in radial bowing, secondary radial head subluxation/dislocation, and ulnar deviation of the carpus.

Question 1028

Topic: Bone Tumors

A 14-year-old boy with polyostotic fibrous dysplasia requires surgical intervention for a progressive shepherd's crook deformity of the proximal femur. Which of the following surgical strategies is most appropriate to minimize the risk of recurrence and implant failure?

. Curettage and packing with cancellous autograft.
. Valgus osteotomy stabilized with a rigid intramedullary nail.
. Valgus osteotomy stabilized with a laterally applied locking plate.
. Curettage and packing with non-vascularized fibular strut graft.
. Resection of the dysplastic segment and endoprosthetic reconstruction.

Correct Answer & Explanation

. Valgus osteotomy stabilized with a rigid intramedullary nail.

Explanation

Correct Answer: Valgus osteotomy stabilized with a rigid intramedullary nail.Surgical management of the shepherd's crook deformity in fibrous dysplasia is challenging due to the poor mechanical quality of the dysplastic bone. Bone grafting (autograft or allograft) alone is contraindicated because the host bone will resorb the graft and replace it with more dysplastic bone. Extramedullary fixation (plates and screws) has a high failure rate because the screws pull out of the weak bone, and the plate acts as a stress riser. The gold standard is a valgus osteotomy to correct the mechanical axis, stabilized with a rigid intramedullary device (like a cephalomedullary nail). This load-sharing construct bypasses the mechanically weak bone and spans the entire length of the femur, significantly reducing the risk of implant failure and recurrent deformity.

Question 1029

Topic: Bone Tumors
An asymptomatic 28-year-old male undergoes a pelvic radiograph following a minor trauma, revealing numerous small, well-defined, symmetric sclerotic foci clustered around the periarticular regions of the pelvis and proximal femurs. If this patient has an associated syndromic presentation, which of the following clinical findings is most likely to be present?
. Café-au-lait spots with smooth borders.
. Subcutaneous hemangiomas.
. Disseminated connective tissue nevi (elastomas).
. Unilateral renal agenesis.
. Blue sclerae.

Correct Answer & Explanation

. Disseminated connective tissue nevi (elastomas).

Explanation

The radiographic description of numerous small, symmetric, periarticular sclerotic foci is pathognomonic for Osteopoikilosis ('spotted bone disease'). It is an autosomal dominant condition often caused by mutations in the LEMD3 gene. While usually asymptomatic and an incidental finding, it can be associated with Buschke-Ollendorff syndrome. This syndrome is characterized by the combination of osteopoikilosis and disseminated connective tissue nevi (elastomas or collagenomas) in the skin. Café-au-lait spots are seen in NF1 and McCune-Albright. Hemangiomas are seen in Maffucci syndrome. Blue sclerae are classic for Osteogenesis Imperfecta.

Question 1030

Topic: Bone Tumors

A 9-year-old girl is diagnosed with Ollier disease after presenting with multiple asymmetric cartilaginous masses in her metaphyseal regions, causing limb length discrepancy. Somatic mosaic mutations in which of the following genes are most strongly implicated in the pathogenesis of her condition?

. EXT1
. GNAS
. IDH1
. LEMD3
. COMP

Correct Answer & Explanation

. IDH1

Explanation

Correct Answer: IDH1Ollier disease (multiple enchondromatosis) is a non-hereditary disorder characterized by multiple enchondromas, typically presenting with asymmetric limb involvement and deformities. It is caused by somatic mosaic mutations in the Isocitrate Dehydrogenase 1 (IDH1) or IDH2 genes. These mutations lead to the accumulation of the oncometabolite D-2-hydroxyglutarate, which interferes with normal chondrocyte differentiation. EXT1 is associated with Multiple Hereditary Exostoses. GNAS is associated with Fibrous Dysplasia. LEMD3 is associated with Osteopoikilosis and Melorheostosis. COMP is associated with Pseudoachondroplasia.

Question 1031

Topic: Bone Tumors
A 12-year-old girl presents with a progressive 'shepherd's crook' deformity of the proximal femur. Radiographs show a characteristic ground-glass appearance of the medullary canal with cortical thinning. Physical examination reveals café-au-lait spots with irregular, 'coast of Maine' borders, and her pediatrician notes a history of precocious puberty. Which of the following best describes the underlying molecular pathogenesis of this patient's condition?
. Mutation in the EXT1 gene leading to abnormal heparan sulfate synthesis.
. Activating mutation in the GNAS1 gene leading to increased intracellular cAMP.
. Mutation in the FGFR3 gene causing constitutive activation of the receptor.
. Defect in the COL1A1 gene leading to abnormal type I collagen synthesis.
. Mutation in the COMP gene affecting cartilage oligomeric matrix protein.

Correct Answer & Explanation

. Activating mutation in the GNAS1 gene leading to increased intracellular cAMP.

Explanation

This patient presents with McCune-Albright syndrome, a severe form of polyostotic fibrous dysplasia associated with endocrinopathies (most commonly precocious puberty) and characteristic café-au-lait spots with irregular borders. The underlying cause of fibrous dysplasia is a somatic, activating mutation in the GNAS1 gene. This mutation leads to a constitutively active Gs-alpha protein, resulting in the overproduction of intracellular cyclic AMP (cAMP). This overproduction disrupts normal osteoblast differentiation, leading to the replacement of normal bone with anarchic, immature fibrous tissue and woven bone. EXT1 mutations cause Multiple Hereditary Exostoses. FGFR3 mutations cause Achondroplasia. COL1A1 defects cause Osteogenesis Imperfecta. COMP mutations cause Pseudoachondroplasia or Multiple Epiphyseal Dysplasia.

Question 1032

Topic: Bone Tumors

A 10-year-old boy with polyostotic fibrous dysplasia presents with a progressive 'shepherd's crook' deformity of the proximal femur and an impending fracture. Which of the following is the most appropriate surgical management strategy for this deformity?

. Curettage and packing with autologous cancellous bone graft.
. Curettage and packing with allograft cancellous bone.
. Valgus producing osteotomy stabilized with a fixed-angle plate and screws.
. Valgus producing osteotomy stabilized with an intramedullary device.
. Observation and bracing until skeletal maturity.

Correct Answer & Explanation

. Valgus producing osteotomy stabilized with an intramedullary device.

Explanation

Correct Answer: Valgus producing osteotomy stabilized with an intramedullary device.Surgical management of the 'shepherd's crook' deformity in fibrous dysplasia is challenging due to the poor quality of the dysplastic bone. The standard of care involves a valgus-producing osteotomy to correct the mechanical axis, stabilized with an intramedullary device (such as a cephalomedullary nail). Intramedullary fixation is preferred over plates and screws because the entire bone is often diseased; plates create stress risers and have a high failure rate in dysplastic bone. Bone grafting (autograft or allograft) is generally contraindicated as a standalone procedure because the graft is rapidly resorbed and replaced by the host's dysplastic fibrous tissue.

Question 1033

Topic: Bone Tumors

In patients with Multiple Hereditary Exostoses (MHE), forearm deformities are common due to the differential growth of the radius and ulna. Which of the following best describes the typical pathoanatomy of the forearm in these patients?

. Relative overgrowth of the ulna with radial head subluxation
. Shortening of the ulna with secondary bowing of the radius and ulnar deviation of the carpus
. Shortening of the radius with secondary bowing of the ulna and radial deviation of the carpus
. Symmetrical shortening of both radius and ulna with a neutral carpus

Correct Answer & Explanation

. Shortening of the ulna with secondary bowing of the radius and ulnar deviation of the carpus

Explanation

Correct Answer: Shortening of the ulna with secondary bowing of the radius and ulnar deviation of the carpusIn Multiple Hereditary Exostoses (MHE), osteochondromas frequently involve the distal forearm. The distal ulna has a smaller cross-sectional area and contributes a larger percentage to the overall longitudinal growth of the bone compared to the radius. Consequently, osteochondroma formation disproportionately retards ulnar growth. This leads to relative shortening of the ulna, secondary bowing of the radius (which continues to grow but is tethered), ulnar deviation of the carpus, and potential radial head subluxation or dislocation (Madelung-like deformity).

Question 1034

Topic: Bone Tumors

A 14-year-old male with polyostotic fibrous dysplasia presents with a progressive 'shepherd's crook' deformity of the proximal femur and a recent impending pathologic fracture. What is the most appropriate surgical strategy for managing this deformity?

. Curettage, autologous bone grafting, and dynamic hip screw fixation
. Valgus-producing proximal femoral osteotomy stabilized with a custom plate and screws
. Valgus-producing proximal femoral osteotomy stabilized with an intramedullary nail
. Resection of the dysplastic bone and reconstruction with a proximal femoral replacement

Correct Answer & Explanation

. Valgus-producing proximal femoral osteotomy stabilized with an intramedullary nail

Explanation

Correct Answer: Valgus-producing proximal femoral osteotomy stabilized with an intramedullary nailThe 'shepherd's crook' deformity is a classic manifestation of fibrous dysplasia in the proximal femur, leading to severe varus and mechanical insufficiency. Surgical correction requires a valgus-producing osteotomy. Because the dysplastic bone is structurally weak and prone to continued remodeling, plate and screw constructs have a high failure rate due to screw pullout. Intramedullary nailing is the biomechanically superior and preferred method of fixation, as it load-shares and protects the entire length of the bone. Autologous bone graft is contraindicated as it will be rapidly resorbed and replaced by dysplastic bone; cortical allograft is preferred if grafting is necessary.

Question 1035

Topic: Bone Tumors

In the medical management of symptomatic polyostotic fibrous dysplasia, intravenous bisphosphonates are frequently utilized. What is the primary established clinical benefit of this pharmacological therapy in these patients?

. Complete radiographic resolution of the ground-glass lesions
. Prevention of the initial development of McCune-Albright syndrome
. Reduction of bone pain and decrease in bone turnover markers
. Restoration of normal lamellar bone architecture within the dysplastic lesions

Correct Answer & Explanation

. Reduction of bone pain and decrease in bone turnover markers

Explanation

Correct Answer: Reduction of bone pain and decrease in bone turnover markersIntravenous bisphosphonates (such as pamidronate or zoledronic acid) are the mainstay of medical treatment for symptomatic fibrous dysplasia. Their primary proven benefits are the significant reduction of bone pain and the normalization of biochemical markers of bone turnover (e.g., alkaline phosphatase). However, bisphosphonates do not cure the disease; they do not lead to radiographic resolution of the lesions, nor do they restore normal lamellar bone architecture or prevent the endocrine manifestations of McCune-Albright syndrome.

Question 1036

Topic: Bone Tumors

A 4-year-old boy presents with a painless, hard, asymmetrical swelling on the medial aspect of his right knee, causing a valgus deformity. Radiographs show an irregular, ossified mass arising off the medial epiphysis of the distal femur. What is the most likely diagnosis?

. Multiple hereditary exostoses
. Ollier disease
. Dysplasia epiphysealis hemimelica
. McCune-Albright syndrome
. Maffucci syndrome

Correct Answer & Explanation

. Dysplasia epiphysealis hemimelica

Explanation

Dysplasia epiphysealis hemimelica (Trevor disease) is characterized by an asymmetric osteochondroma-like overgrowth arising directly from the epiphysis, most commonly affecting the medial side of the knee or ankle in young boys.

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