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Bone Tumors MCQs

Practice Set 4 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 61

Topic: Bone Tumors

A 16-year-old male presents with deep thigh pain that is worse at night and dramatically relieved by ibuprofen. Radiographs show a small radiolucent nidus surrounded by dense reactive sclerosis in the proximal femur. Which imaging modality is best for localizing the nidus prior to ablation?

. MRI with gadolinium
. Thin-slice CT scan
. Ultrasound
. Bone scintigraphy
. PET scan

Correct Answer & Explanation

. Thin-slice CT scan

Explanation

A thin-slice CT scan is the imaging modality of choice to clearly delineate the nidus of an osteoid osteoma and differentiate it from the surrounding reactive sclerosis. This is essential for planning surgical resection or radiofrequency ablation.

Question 62

Topic: Bone Tumors

An 18-year-old presents with dull back pain not significantly relieved by NSAIDs. Imaging reveals an expansile 3.5 cm radiolucent lesion in the posterior elements of L3. Histology is identical to an osteoid osteoma. What is the most likely diagnosis?

. Osteosarcoma
. Chondroblastoma
. Osteoblastoma
. Aneurysmal bone cyst
. Giant cell tumor

Correct Answer & Explanation

. Osteoblastoma

Explanation

Osteoblastomas are histologically indistinguishable from osteoid osteomas but are larger (typically > 2 cm). They are frequently located in the posterior elements of the spine and cause pain that is less responsive to salicylates/NSAIDs.

Question 63

Topic: Bone Tumors

A 25-year-old patient undergoes a radiographic workup for right thigh pain. The femur shows an intramedullary expansile lesion with a "ground-glass" appearance, cortical thinning, and bowing.

What is the most definitive molecular feature associated with this condition?

. EXT1/EXT2 gene mutation
. GNAS gene missense mutation
. COL1A1 gene mutation
. FGF23 overproduction
. t(11;22) translocation

Correct Answer & Explanation

. GNAS gene missense mutation

Explanation

The "ground-glass" appearance and bowing are classic radiographic hallmarks of fibrous dysplasia. The underlying molecular defect is a somatic activating missense mutation in the GNAS gene, leading to elevated intracellular cAMP.

Question 64

Topic: Bone Tumors
A 9-year-old girl presents with a leg length discrepancy and precocious puberty. Examination reveals large, irregular hyperpigmented macules with a 'coast of Maine' border. Radiographs demonstrate polyostotic medullary lesions with a 'ground-glass' appearance. Which of the following gene mutations is pathognomonic for this condition?
. GNAS1
. EXT1
. USP6
. RUNX2
. SH3BP2

Correct Answer & Explanation

. GNAS1

Explanation

McCune-Albright syndrome is characterized by polyostotic fibrous dysplasia, precocious puberty, and café-au-lait spots. It is caused by an activating somatic mutation in the GNAS1 gene.

Question 65

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 worsening hip pain. What is the most reliable surgical strategy to correct the deformity and prevent recurrence?

. Valgus osteotomy and plate fixation
. Curettage and autologous bone grafting
. Curettage and non-vascularized fibular strut graft
. Valgus osteotomy with intramedullary nailing
. Total hip arthroplasty

Correct Answer & Explanation

. Valgus osteotomy with intramedullary nailing

Explanation

In fibrous dysplasia, cortical bone grafts are frequently resorbed and replaced by dysplastic bone. The most reliable treatment for a shepherd's crook deformity involves valgus-producing osteotomies stabilized with intramedullary nails spanning the entire femur.

Question 66

Topic: Bone Tumors
Jaffe-Campanacci syndrome is characterized by the presence of multiple non-ossifying fibromas. What other clinical manifestations are classically associated with this syndrome?
. Precocious puberty and café-au-lait spots
. Mental retardation, café-au-lait spots, and hypogonadism
. Intramuscular myxomas and precocious puberty
. Multiple osteochondromas and short stature
. Soft tissue hemangiomas and enchondromas

Correct Answer & Explanation

. Mental retardation, café-au-lait spots, and hypogonadism

Explanation

Jaffe-Campanacci syndrome is a rare disorder characterized by multiple non-ossifying fibromas, café-au-lait spots (similar to neurofibromatosis), mental retardation, hypogonadism, and cardiovascular abnormalities.

Question 67

Topic: Bone Tumors

A 9-year-old boy presents with acute arm pain after throwing a baseball. Radiographs show a centrally located, completely radiolucent metaphyseal lesion in the proximal humerus with a cortical fracture and a cortical fragment settling in the dependent portion of the lesion.

What is the most likely diagnosis?

. Aneurysmal bone cyst
. Fibrous dysplasia
. Unicameral bone cyst
. Eosinophilic granuloma
. Osteosarcoma

Correct Answer & Explanation

. Unicameral bone cyst

Explanation

A Unicameral Bone Cyst (UBC) is a centrally located metaphyseal lesion that commonly presents with a pathologic fracture in the proximal humerus. The 'fallen leaf' or 'fallen fragment' sign is pathognomonic for a UBC.

Question 68

Topic: Bone Tumors

A 15-year-old female presents with progressive knee pain. MRI reveals an eccentric metaphyseal lesion in the proximal tibia demonstrating multiple fluid-fluid levels on T2-weighted images.

Histology will most likely reveal which of the following?

. Stroma with CD1a positive histiocytes
. Atypical spindle cells producing osteoid
. Blood-filled spaces lined by endothelium
. Blood-filled spaces lacking endothelial lining
. Cartilage lobules with focal calcification

Correct Answer & Explanation

. Blood-filled spaces lacking endothelial lining

Explanation

The clinical and radiographic findings (fluid-fluid levels) are classic for an Aneurysmal Bone Cyst (ABC). Histologically, ABCs are characterized by cavernous, blood-filled spaces that are separated by septa and notably lack an endothelial lining.

Question 69

Topic: Bone Tumors
A 14-year-old female presents with multiple bone lesions, irregular hyperpigmented skin macules, and a history of precocious puberty. What is the underlying genetic mechanism of her condition?
. Mutation in the EXT1 gene
. Post-zygotic activating mutation in the GNAS gene
. Germline mutation in the NF1 gene
. Mutation in the FGFR3 gene
. Translocation t(11;22)

Correct Answer & Explanation

. Post-zygotic activating mutation in the GNAS gene

Explanation

McCune-Albright syndrome is characterized by polyostotic fibrous dysplasia, café-au-lait spots, and endocrine abnormalities. It is caused by a post-zygotic somatic activating mutation in the GNAS gene.

Question 70

Topic: Bone Tumors

In a 15-year-old patient with progressive Shepherd's crook deformity of the proximal femur due to fibrous dysplasia, what is the biomechanically preferred method of surgical stabilization?

. Curettage, cancellous autografting, and plate fixation
. Valgus osteotomy and intramedullary nailing
. External fixation
. Isolated curettage and cementation
. Observation and long-leg bracing

Correct Answer & Explanation

. Valgus osteotomy and intramedullary nailing

Explanation

Valgus osteotomy corrects the deformity, while intramedullary nailing provides a load-sharing construct spanning the entire bone length. Plating (load-bearing) frequently fails in the weak dysplastic bone.

Question 71

Topic: Bone Tumors

Aside from precocious puberty, which of the following endocrinopathies is most frequently seen in patients with McCune-Albright syndrome?

. Hypoparathyroidism
. Hyperthyroidism
. Type 1 Diabetes Mellitus
. Addison's disease
. Pheochromocytoma

Correct Answer & Explanation

. Hyperthyroidism

Explanation

Hyperthyroidism is the second most common endocrine abnormality in McCune-Albright syndrome. Others include Cushing's syndrome, acromegaly, and hypophosphatemic rickets.

Question 72

Topic: Bone Tumors
The cutaneous lesions associated with McCune-Albright syndrome can be clinically differentiated from those seen in Neurofibromatosis type 1 by which of the following characteristics?
. They are uniformly elevated and palpable.
. They frequently cross the midline of the body.
. They have irregular, jagged borders.
. They primarily affect the palms and soles.
. They fade completely following puberty.

Correct Answer & Explanation

. They have irregular, jagged borders.

Explanation

The café-au-lait macules in McCune-Albright syndrome typically have irregular, jagged borders ('Coast of Maine') and often respect the midline, whereas those in NF1 have smooth ('Coast of California') borders.

Question 73

Topic: Bone Tumors
In which of the following molecules is McCune-Albright syndrome due to a mutation?
. Fibroblast growth factor receptor protein
. GNAS1
. Bone morphogenetic protein
. Fibrillin
. Collagen type 1

Correct Answer & Explanation

. GNAS1

Explanation

McCune-Albright syndrome (also known as polyostotic fibrous dysplasia) is due to a mutation in GNAS1. GNAS1 is the alpha subunit of GS, which is a protein that links receptors to adenyl cyclase activity.

Question 74

Topic: Bone Tumors

Dysplasia epiphysialis hemimelia (Trevor disease) is a rare developmental disorder of the epiphysis. Histologically, the lesions of Trevor disease most closely resemble which of the following?

. Osteoid osteoma
. Osteochondroma
. Chondroblastoma
. Enchondroma
. Osteosarcoma

Correct Answer & Explanation

. Osteochondroma

Explanation

Trevor disease is characterized by asymmetric epiphyseal cartilage overgrowth. Histologically, it is identical to an osteochondroma, displaying a hyaline cartilage cap with underlying enchondral ossification.

Question 75

Topic: Bone Tumors
Which of the following conditions is represented in this radiograph of a child's neck?
. Osteoid osteoma of C1
. Jefferson's fracture
. Rotatory subluxation
. Hangman fracture
. Os odontoideum

Correct Answer & Explanation

. Rotatory subluxation

Explanation

This radiograph indicates a rotatory subluxation of a child's neck. Alteration of the cortical ring of the anterior atlas is present and superimposed on the lateral mass of atlas. Increased distance between the anterior atlas and axis is the result of rotation.

Question 76

Topic: Bone Tumors
The lesion indicated in this computed tomography most likely represents:
. Brodie's abscess
. Eosinophilic granuloma
. Osteosarcoma
. Osteoid osteoma
. Osteoma

Correct Answer & Explanation

. Osteoid osteoma

Explanation

This patient has an osteoid osteoma with pain in the lumbar spine where the lesion is located. The patient's osteoid osteoma shows hot on a photon emission computed tomography scan and is relieved by nonsteroidal anti-inflammatory agents. Most patients with osteoid osteoma with lesions have them in the posterior region of their vertebrae.

Question 77

Topic: Bone Tumors
In which pattern does the most common presentation of Trevor's disease occur:
. Generalized involvement of all extremities
. Distal medial areas of one lower extremity
. Proximal lateral areas of both lower extremities
. Distal medial areas of both upper extremities
. Proximal lateral areas of one upper extremity

Correct Answer & Explanation

. Distal medial areas of one lower extremity

Explanation

Trevor's disease, also known as dysplasia epiphysialis hemimelia, refers to epiphyseal osteochondromas. Epiphyseal osteochondromas are usually few in number and are more common on the distal and medial portions of the epiphysis of one lower extremity.

Question 78

Topic: Bone Tumors
Epiphyseal osteochondroma is also known as:
. Maffucci's syndrome
. Freiberg's fracture
. Larsen-Johansson disease
. Trevor's disease
. Iselin's disease

Correct Answer & Explanation

. Trevor's disease

Explanation

Epiphyseal osteochondroma is also known as Trevor's disease. Epiphyseal osteochondroma is localized to a specific region of the body, unlike multiple osteochondroma, which affects the entire body. Epiphyseal osteochondroma and multiple osteochondroma are unrelated disorders.

Question 79

Topic: Bone Tumors
An 18-year-old man has chronic pain in his right thigh, which is foreshortened with an increased anterior bow. What is the most likely diagnosis?
. Chronic osteomyelitis
. Osteogenesis imperfecta
. Paget's disease
. Multiple enchondromas
. Fibrous dysplasia

Correct Answer & Explanation

. Fibrous dysplasia

Explanation

This patient has polyostotic fibrous dysplasia. The diffuse enlargement in width is atypical for osteogenesis imperfecta or infection. Paget's disease is associated with increased sclerosis. Enchondromas produce more localized changes in the bones than fibrous dysplasia.

Question 80

Topic: Bone Tumors

A 12-year-old boy presents with night pain in his proximal tibia that is relieved by NSAIDs. Radiographs show a sclerotic lesion with a 1 cm radiolucent nidus. What is the most likely diagnosis?

. Osteoblastoma
. Osteosarcoma
. Osteoid osteoma
. Brodie's abscess
. Chondroblastoma

Correct Answer & Explanation

. Osteoid osteoma

Explanation

Night pain relieved by NSAIDs and a radiolucent nidus <1.5 cm surrounded by reactive sclerosis are pathognomonic for osteoid osteoma.

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