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Bone Tumors MCQs

Practice Set 3 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 41

Topic: Bone Tumors
The radiograph (Slide 1) of an 11-year-old boy with significant leg pain is presented. No other abnormalities are found during the patient's history or physical examination. The most likely diagnosis is:
. Osteomyelitis
. Fibrous dysplasia
. Enchondroma
. Unicameral bone cyst
. Ewing sarcoma

Correct Answer & Explanation

. Fibrous dysplasia

Explanation

Fibrous dysplasia is chronically expansile with vague transition to normal bone and a 'ground-glass' appearance. These characteristics differentiate fibrous dysplasia from aneurysmal and unicameral bone cysts. Additionally, the lack of periosteal reaction differentiates fibrous dysplasia from malignancy or osteomyelitis. The patient's magnetic resonance image (Slide 2) is also provided.

Question 42

Topic: Bone Tumors

A 10-year-old boy presents with thigh pain that is worse at night and relieved dramatically by ibuprofen. Radiographs demonstrate a small radiolucent nidus surrounded by dense reactive sclerosis in the proximal femur.

What is the preferred definitive treatment if symptoms are refractory to medical management?

. En bloc resection
. Chemotherapy
. Radiofrequency ablation
. Radiation therapy
. Curettage and bone grafting

Correct Answer & Explanation

. Radiofrequency ablation

Explanation

The presentation is classic for an osteoid osteoma. Radiofrequency ablation (RFA) is the minimally invasive treatment of choice for symptomatic lesions failing conservative management.

Question 43

Topic: Bone Tumors

A 9-year-old boy sustains a minor fall and presents with arm pain. Radiographs reveal a mildly displaced pathologic fracture through a central, radiolucent, well-circumscribed lesion in the proximal humerus with a "fallen leaf" sign. What is the most likely diagnosis?

. Aneurysmal bone cyst
. Unicameral bone cyst
. Non-ossifying fibroma
. Fibrous dysplasia
. Osteosarcoma

Correct Answer & Explanation

. Unicameral bone cyst

Explanation

A unicameral (simple) bone cyst is centrally located in the metaphysis of long bones in children. The "fallen leaf" or "fallen fragment" sign is pathognomonic for a pathologic fracture through the cyst.

Question 44

Topic: Bone Tumors

A 9-year-old boy presents with shoulder pain after a minor fall. Radiographs reveal a centrally located, radiolucent metaphyseal lesion in the proximal humerus with a cortical fragment resting at the bottom of the cyst. What is the most likely diagnosis?

. Aneurysmal bone cyst
. Unicameral bone cyst
. Non-ossifying fibroma
. Osteosarcoma
. Chondroblastoma

Correct Answer & Explanation

. Unicameral bone cyst

Explanation

The 'fallen leaf' or 'fallen fragment' sign is pathognomonic for a unicameral bone cyst (UBC). It occurs when a fractured cortical fragment drops into the fluid-filled cavity of the cyst.

Question 45

Topic: Bone Tumors

An 8-year-old girl fractures her right femur when starting a sprint. Based on her radiograph (Slide), which of the following is the most likely diagnosis:

. Unicameral bone cyst
. Aneurysmal bone cyst
. Osteogenic sarcoma
. Fibrous dysplasia
. Normal pre-existing bone

Correct Answer & Explanation

. Fibrous dysplasia

Explanation

This patient has signs of a pre-existing fibrous dysplasia lesion, including a central expansion of the subtrochanteric region with a ground-glass (not lucent) appearance. She was diagnosed with fibrous dysplasia.

Question 46

Topic: Bone Tumors
The patient presented in the radiograph (Slide) has a slight, painless limp. Which of the following is the most likely diagnosis:
. Ollier disease
. Osteogenesis imperfecta
. Fibrous dysplasia
. Neurofibromatosis
. Fibrous cortical defects

Correct Answer & Explanation

. Fibrous dysplasia

Explanation

This patient has multiple "ground-glass" lesions and one cystic lesion, as well as bowing in the subtrochanteric region. The patient was diagnosed with fibrous dysplasia.

Question 47

Topic: Bone Tumors

A 10-year-old child, who has no history of fever, trauma, or infection, presents with minimal pain and a Trendelenburg gait on the left (Slide). Which of the following is the most likely diagnosis:

. Aneurysmal bone cyst
. Chronic osteomyelitis
. Fibrous dysplasia
. Unicameral bone cyst
. Enchondroma

Correct Answer & Explanation

. Fibrous dysplasia

Explanation

This patient has fibrous dysplasia. The diffuse nature of the changes over a long portion of the bone, which includes blurring and thinning of the cortex, are classic signs of the disorder.

Question 48

Topic: Bone Tumors

The lesion shown in the radiograph (pic) most likely represents which of the following processes:

. Aneurysmal bone cyst
. Fibrous dysplasia
. Unicameral bone cyst
. Osteomyelitis
. Fibrous cortical defect

Correct Answer & Explanation

. Unicameral bone cyst

Explanation

The lesion shown in the radiograph is a unicameral bone cyst. The diagnosis was confirmed by aspiration and the subsequent response, filling in after autogenous marrow (pic).An aneurysmal bone cyst is typically more septated and expansile in width, fibrous dysplasia has a more blurred zone of transition and ground-glass appearance, and a fibrous cortical defect is more eccentrically placed.

Question 49

Topic: Bone Tumors
A 12-year-old patient with fibrous dysplasia has an increasing limp and progressive bowing in the intertrochanteric and subtrochanteric regions of his femur. Recommended treatment includes:
. Allograft strut graft in situ
. Plate fixation in situ
. Rod fixation in situ
. Valgus osteotomy with plate and/or rod
. Hip arthrodesis in straight position

Correct Answer & Explanation

. Valgus osteotomy with plate and/or rod

Explanation

The most important step in treating patients with fibrous dysplasia is to decrease the bending force on the patient's femur. A valgus osteotomy with a plate or a rod decreases the bending force on the patient's femur by decreasing the offset from the center of the patient's body mass. Allografting and plate or rod fixation in situ causes progressive bowing in the patient.

Question 50

Topic: Bone Tumors

Which of the following bones is the most common site for involvement with fibrous dysplasia:

. Phalanges of the hand
. Radius
. Ulna
. Humerus
. Femur

Correct Answer & Explanation

. Femur

Explanation

The femur and the tibia are the most common sites of fibrous dysplasia in the appendicular skeleton. Involvement of the humerus is also common. Fibrous dysplasia may also occur in the radius, ulna, and phalanges of the hand; it occurs less frequently in the femur, humerus, and pelvis.

Question 51

Topic: Bone Tumors

The pattern of genetic transmission of polyostotic fibrous dysplasia is best described as:

. Autosomal dominant with high penetrance
. Autosomal dominant with low penetrance
. Autosomal recessive
. Sex-linked dominant
. No genetic transmission (sporadic)

Correct Answer & Explanation

. No genetic transmission (sporadic)

Explanation

Fibrous dysplasia is a sporadic condition. Although there are a few reports of parents and children having fibrous dysplasia, such reports are rare.

Question 52

Topic: Bone Tumors

Which of the following conditions does this computerizd tomography scan (Slide) most likely represent:

. Brodies abscess
. Osteosarcoma
. Fibrous dysplasia
. Osteoid osteoma
. Enchondromas

Correct Answer & Explanation

. Osteoid osteoma

Explanation

This is an osteoid osteoma of the fourth lumbar vertebra in a patient who experienced night pain and relieved the pain with nonsteroidal anti- inflammatory drugs. The location of a sclerotic nidus in the posterior elements of the vertebrae is typical for this disorder. Excision of the osteoid osteoma resulted in prompt pain relief for this patient.

Question 53

Topic: Bone Tumors

Which of the following histologic features best differentiates osteofibrous dysplasia from fibrous dysplasia?

. Presence of a cartilaginous cap
. Osteoblastic rimming of the bone trabeculae
. Biphasic appearance with epithelial cells
. Mosaic pattern of cement lines
. Absence of woven bone

Correct Answer & Explanation

. Osteoblastic rimming of the bone trabeculae

Explanation

Unlike fibrous dysplasia, which lacks osteoblastic rimming around its irregular woven bone trabeculae, osteofibrous dysplasia demonstrates prominent osteoblastic rimming. Both present as fibro-osseous lesions, but this histologic distinction is critical for diagnosis.

Question 54

Topic: Bone Tumors

A 14-year-old boy with polyostotic fibrous dysplasia presents with increasing thigh pain and a severe varus deformity of the proximal femur (Shepherd's crook deformity).

What is the most appropriate surgical management?

. Curettage and bone grafting with allograft
. Open reduction and internal fixation with a dynamic hip screw
. Valgus osteotomy stabilized with an intramedullary nail
. Resection and endoprosthetic reconstruction
. Observation and bisphosphonate therapy

Correct Answer & Explanation

. Valgus osteotomy stabilized with an intramedullary nail

Explanation

The standard surgical treatment for a progressive Shepherd's crook deformity in fibrous dysplasia involves a valgus-producing osteotomy stabilized with a cephalomedullary or intramedullary nail. Cortical bone grafting and plating alone have unacceptably high failure rates in these mechanically inferior bones.

Question 55

Topic: Bone Tumors

A 9-year-old girl with polyostotic fibrous dysplasia presents with precocious puberty and cafe-au-lait spots. What is the underlying genetic mechanism of her condition?

. Mutation in the EXT1 gene
. Mutation in the GNAS1 gene
. Mutation in the NF1 gene
. Mutation in the p53 gene
. Mutation in the RB1 gene

Correct Answer & Explanation

. Mutation in the GNAS1 gene

Explanation

This patient has McCune-Albright syndrome. The condition is caused by an activating somatic missense mutation in the GNAS1 gene, resulting in persistent cAMP production and widespread endocrine, cutaneous, and skeletal abnormalities.

Question 56

Topic: Bone Tumors

A 15-year-old boy presents with a prominent limp and shortening of his right leg. Radiographs demonstrate a classic "shepherd's crook" deformity of the proximal femur.

What is the preferred surgical approach for an impending fracture in this patient?

. Curettage and cancellous bone grafting alone
. Cortical strut allograft, valgus-producing osteotomy, and internal fixation
. Wide en bloc resection and endoprosthetic reconstruction
. Percutaneous pinning in situ
. Observation and bracing until skeletal maturity

Correct Answer & Explanation

. Cortical strut allograft, valgus-producing osteotomy, and internal fixation

Explanation

Surgical management of a shepherd's crook deformity requires correction of the mechanical axis via valgus osteotomy and rigid internal fixation. Cortical strut grafts are preferred over cancellous grafts to prevent resorption and recurrence.

Question 57

Topic: Bone Tumors

How do the cafe-au-lait spots seen in McCune-Albright syndrome typically differ from those seen in Neurofibromatosis type 1 (NF1)?

. They have smooth "coast of California" borders
. They have irregular "coast of Maine" borders
. They are predominantly found on the palms and soles
. They are strictly bilateral and symmetrical
. They fade completely after puberty

Correct Answer & Explanation

. They have irregular "coast of Maine" borders

Explanation

Cafe-au-lait macules in McCune-Albright syndrome typically have irregular, jagged borders resembling the "coast of Maine." In contrast, those in NF1 have smooth borders resembling the "coast of California."

Question 58

Topic: Bone Tumors

A 7-year-old boy has an incidentally discovered unicameral bone cyst (UBC) in the proximal humerus. Radiographs show the cyst is located immediately adjacent to the physis. Which of the following best describes this cyst?

. Latent cyst
. Active cyst
. Aneurysmal bone cyst
. Giant cell tumor
. Chondroblastoma

Correct Answer & Explanation

. Active cyst

Explanation

An active UBC is located immediately adjacent to the epiphyseal plate and has a higher risk of interfering with growth or recurring after treatment. A latent cyst has migrated away from the physis into the diaphysis.

Question 59

Topic: Bone Tumors

A 9-year-old boy presents with mild shoulder pain after throwing a baseball. Radiographs reveal a centrally located, lucent lesion in the proximal humerus with a cortical fragment resting dependently within the lesion. What is the most likely diagnosis?

. Aneurysmal bone cyst
. Non-ossifying fibroma
. Unicameral bone cyst
. Osteosarcoma
. Eosinophilic granuloma

Correct Answer & Explanation

. Unicameral bone cyst

Explanation

The "fallen leaf" or "fallen fragment" sign is pathognomonic for a unicameral bone cyst that has sustained a pathologic fracture. It occurs because the cyst cavity is fluid-filled, allowing the cortical fragment to settle at the base.

Question 60

Topic: Bone Tumors

Primary aneurysmal bone cysts (ABCs) are now recognized as true neoplasms. Which of the following genetic translocations is most frequently associated with primary ABCs?

. t(11;22)
. t(X;18)
. t(16;17)
. t(12;16)
. t(9;22)

Correct Answer & Explanation

. t(16;17)

Explanation

Primary ABCs are driven by the t(16;17) translocation, which fuses the promoter of the CDH11 gene to the USP6 oncogene, leading to USP6 upregulation.

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