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Bone Tumors MCQs

Practice Set 9 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 161

Topic: Bone Tumors

A 12-year-old girl presents with precocious puberty, cafe-au-lait spots with irregular borders, and a newly discovered lytic lesion in her proximal femur resulting in a 'shepherd's crook' deformity. What is the underlying genetic and pathophysiologic mechanism of this patient's skeletal disease?

. Mutation in the EXT1 gene leading to abnormal heparan sulfate synthesis
. Activating mutation of the GNAS gene resulting in increased intracellular cAMP
. Inactivating mutation of the PTEN gene leading to overactive mTOR signaling
. Overproduction of FGF-23 causing renal phosphate wasting
. Defect in Type I collagen synthesis leading to brittle bones

Correct Answer & Explanation

. Activating mutation of the GNAS gene resulting in increased intracellular cAMP

Explanation

This patient has McCune-Albright syndrome, characterized by polyostotic fibrous dysplasia, precocious puberty, and cafe-au-lait spots. The underlying cause is a somatic activating mutation in the GNAS gene, which continuously activates Gs-alpha, leading to elevated intracellular cAMP levels.

Question 162

Topic: Bone Tumors

A 12-year-old girl is diagnosed with polyostotic fibrous dysplasia and precocious puberty. What is the underlying molecular pathogenesis of her musculoskeletal condition?

. Activating mutation in GNAS gene causing decreased cAMP
. Activating mutation in GNAS gene causing increased cAMP
. Inactivating mutation in EXT1 gene
. Mutation in FGFR3 gene
. Mutation in COL1A1 gene

Correct Answer & Explanation

. Activating mutation in GNAS gene causing increased cAMP

Explanation

McCune-Albright syndrome involves a post-zygotic activating mutation in the GNAS gene, leading to continuous activation of the Gs alpha protein. This results in an overproduction of cAMP, driving the characteristic bone lesions and endocrinopathies.

Question 163

Topic: Bone Tumors

A 30-year-old male requires surgical stabilization of a progressive "shepherd's crook" deformity of the proximal femur due to fibrous dysplasia. Which of the following principles is most critical for surgical success?

. Use of rigid plate osteosynthesis
. Prophylactic radiation therapy to prevent recurrence
. Use of intramedullary fixation and cortical bone strut allograft
. Use of intramedullary fixation and cancellous autograft
. Marginal wide resection of the affected bone

Correct Answer & Explanation

. Use of intramedullary fixation and cortical bone strut allograft

Explanation

In fibrous dysplasia, intramedullary fixation is preferred over plating to prevent peri-implant fractures. Cortical bone allograft is favored over cancellous bone, as the dysplastic process tends to rapidly resorb cancellous graft.

Question 164

Topic: Bone Tumors

A 14-year-old male with McCune-Albright syndrome presents with progressive lower extremity bowing and diffuse bone pain. Laboratory evaluation reveals hypophosphatemia, normal serum calcium, and elevated alkaline phosphatase. Which of the following mediators is most likely responsible for his metabolic bone abnormalities?

. Parathyroid hormone (PTH)
. Fibroblast growth factor 23 (FGF-23)
. 1,25-dihydroxyvitamin D
. Calcitonin
. Sclerostin

Correct Answer & Explanation

. Fibroblast growth factor 23 (FGF-23)

Explanation

Patients with fibrous dysplasia can develop hypophosphatemic rickets/osteomalacia due to the overproduction of FGF-23 by the dysplastic lesional tissue. FGF-23 causes renal phosphate wasting and decreases active vitamin D levels.

Question 165

Topic: Bone Tumors

A 32-year-old female with known polyostotic fibrous dysplasia presents with worsening right groin pain. Radiographs demonstrate a severe varus deformity of the proximal femur ("Shepherd's crook" deformity) with extensive cortical thinning, but no acute fracture is seen. What is the most appropriate surgical management?

. Extensive curettage and filling with structural allograft.
. Valgus-producing proximal femoral osteotomy stabilized with an intramedullary nail.
. Open reduction and internal fixation with a sliding hip screw device.
. Total hip arthroplasty with a diaphyseal-fitting stem.
. Observation and initiation of intravenous bisphosphonates.

Correct Answer & Explanation

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

Explanation

A Shepherd's crook deformity places severe biomechanical stress on the proximal femur, risking pathologic fracture. The preferred surgical treatment is a valgus-producing osteotomy to correct the mechanical axis, stabilized by an intramedullary nail to protect the entire length of the dysplastic femur.

Question 166

Topic: Bone Tumors

A 14-year-old male presents with progressive left knee pain and a distal femoral mass. Initial plain radiographs of the left distal femur are shown below.

Based on these images and the clinical presentation, which of the following radiographic features is MOST characteristic of the likely diagnosis?

. A purely lytic lesion with a narrow zone of transition.
. A 'soap bubble' appearance with internal septations.
. A prominent 'sunburst' periosteal reaction and Codman's triangle.
. A smooth, lamellated 'onion-skin' periosteal reaction.
. A well-defined sclerotic border with central lucency.

Correct Answer & Explanation

. A prominent 'sunburst' periosteal reaction and Codman's triangle.

Explanation

Correct Answer: CThe plain radiographs in the case description explicitly detail a 'prominent 'sunburst' or 'hair-on-end' periosteal reaction' and a 'distinct Codman's triangle' along with a mixed lytic and blastic appearance and cortical destruction. These features are classic radiographic hallmarks of osteosarcoma, indicating a rapidly aggressive tumor that is lifting the periosteum and producing new bone in a disorganized fashion. Options A and E describe features more typical of benign or less aggressive lesions (e.g., non-ossifying fibroma, fibrous dysplasia). Option B ('soap bubble' appearance) is characteristic of giant cell tumor or aneurysmal bone cyst. Option D ('onion-skin' periosteal reaction) is a classic feature of Ewing sarcoma, which typically presents with a permeative lytic pattern and is often diaphyseal or metadiaphyseal.

Question 167

Topic: Bone Tumors

Which of the following genetic syndromes is characterized by a mutation in the RECQL4 helicase gene, presenting with poikiloderma and an increased risk of developing osteosarcoma?

. Li-Fraumeni syndrome
. Rothmund-Thomson syndrome
. Hereditary retinoblastoma
. McCune-Albright syndrome
. Multiple hereditary exostoses

Correct Answer & Explanation

. Rothmund-Thomson syndrome

Explanation

Rothmund-Thomson syndrome is an autosomal recessive condition caused by RECQL4 mutations. It is associated with rash, sparse hair, and a high risk of osteosarcoma.

Question 168

Topic: Bone Tumors

An 18-year-old male presents with a slow-growing mass on the diaphyseal surface of his proximal tibia. Imaging reveals a broad-based, surface-dwelling lesion with perpendicular periosteal reactions. Biopsy demonstrates an intermediate-grade spindle cell proliferation with a predominantly chondroblastic matrix. What is the diagnosis?

. Parosteal osteosarcoma
. Periosteal osteosarcoma
. High-grade surface osteosarcoma
. Osteochondroma
. Chondrosarcoma

Correct Answer & Explanation

. Periosteal osteosarcoma

Explanation

Periosteal osteosarcoma is a rare, intermediate-grade surface lesion with a predominantly chondroblastic matrix. It typically affects the diaphysis and has a prognosis intermediate between parosteal and conventional osteosarcoma.

Question 169

Topic: Bone Tumors

Which of the following variants of osteosarcoma is characterized as an intermediate-grade, chondroblastic surface lesion that typically presents on the diaphyseal surface of the tibia or femur?

. Parosteal osteosarcoma
. Periosteal osteosarcoma
. Telangiectatic osteosarcoma
. High-grade surface osteosarcoma
. Secondary osteosarcoma

Correct Answer & Explanation

. Periosteal osteosarcoma

Explanation

Periosteal osteosarcoma is an intermediate-grade surface tumor that predominantly demonstrates chondroblastic differentiation. It typically arises on the diaphysis of long bones and has a slightly worse prognosis than parosteal osteosarcoma.

Question 170

Topic: Bone Tumors

The standard neoadjuvant and adjuvant chemotherapy regimen for high-grade conventional osteosarcoma (MAP protocol) consists of which of the following agents?

. Methotrexate, Doxorubicin, Cisplatin
. Ifosfamide, Etoposide, Carboplatin
. Vincristine, Doxorubicin, Cyclophosphamide
. Paclitaxel, Docetaxel, Gemcitabine
. Imatinib, Sunitinib, Sorafenib

Correct Answer & Explanation

. Methotrexate, Doxorubicin, Cisplatin

Explanation

The MAP regimen, which is standard of care for conventional osteosarcoma in children and young adults, stands for High-dose Methotrexate, Doxorubicin (Adriamycin), and Cisplatin.

Question 171

Topic: Bone Tumors

A 16-year-old male is suspected of having a conventional high-grade osteosarcoma of the distal femur based on local plain radiographs and MRI. Staging studies are mandatory before initiating treatment. Which of the following sites is the most common location for initial metastasis in this disease?

. Liver
. Lungs
. Brain
. Regional lymph nodes
. Contralateral femur

Correct Answer & Explanation

. Lungs

Explanation

The most common site of metastasis for conventional osteosarcoma is the lungs. Consequently, high-resolution CT of the chest is an essential component of the initial staging workup.

Question 172

Topic: Bone Tumors

A 17-year-old male is undergoing multi-agent neoadjuvant chemotherapy for conventional osteosarcoma. His regimen includes Methotrexate, Doxorubicin, and Cisplatin. Routine monitoring for an irreversible side effect of Doxorubicin requires which of the following surveillance studies?

. Echocardiogram
. Audiogram
. Pulmonary function tests
. Renal ultrasound
. Hepatic transaminases

Correct Answer & Explanation

. Echocardiogram

Explanation

Doxorubicin (Adriamycin) is known to cause dose-dependent, irreversible cardiotoxicity (cardiomyopathy). Patients require routine echocardiography to monitor cardiac function (ejection fraction) during and after treatment.

Question 173

Topic: Bone Tumors

A 16-year-old male with a history of high-grade osteosarcoma of the distal femur treated with limb-salvage and chemotherapy presents for his 1-year follow-up. He is asymptomatic, but a routine surveillance scan reveals a new finding. Which of the following organs is the most common site of metastasis for this disease?

. Liver
. Lungs
. Brain
. Kidneys
. Spine

Correct Answer & Explanation

. Lungs

Explanation

The most common site for osteosarcoma metastasis is the lungs. Routine surveillance includes chest CTs, and isolated pulmonary metastases are often treated with aggressive surgical metastasectomy if feasible.

Question 174

Topic: Bone Tumors

A 16-year-old boy complains of progressive right thigh pain that is distinctly worse at night and dramatically relieved by ibuprofen. Radiographs reveal a cortical thickening with a small 8mm radiolucent nidus. What is the most appropriate definitive minimally invasive treatment?

. Wide surgical resection
. Intralesional curettage and bone grafting
. Radiofrequency ablation
. External beam radiation
. Systemic chemotherapy

Correct Answer & Explanation

. Radiofrequency ablation

Explanation

The clinical and radiographic presentation is classic for an osteoid osteoma. Radiofrequency ablation (RFA) is the current gold standard minimally invasive definitive treatment, offering high success rates and low morbidity compared to surgical resection.

Question 175

Topic: Bone Tumors

A 14-year-old boy presents with progressive knee pain. Radiographs reveal a sunburst periosteal reaction and Codman's triangle in the distal femoral metaphysis. A biopsy confirms high-grade osteosarcoma. What is the standard sequence of treatment?

. Amputation followed by radiation
. Neoadjuvant chemotherapy followed by wide surgical resection and adjuvant chemotherapy
. Wide surgical resection followed by radiation
. Radiation therapy followed by chemotherapy
. Primary wide surgical resection alone

Correct Answer & Explanation

. Neoadjuvant chemotherapy followed by wide surgical resection and adjuvant chemotherapy

Explanation

The standard of care for high-grade osteosarcoma includes neoadjuvant chemotherapy, followed by wide surgical resection (limb salvage if possible), and then adjuvant chemotherapy. Radiation has a minimal role as osteosarcoma is highly radioresistant.

Question 176

Topic: Bone Tumors

A 14-year-old boy presents with severe, aching pain in his right thigh that is worse at night and rapidly relieved by ibuprofen. Radiographs demonstrate diaphyseal cortical thickening with a 1-centimeter radiolucent nidus. What is the primary biochemical mediator responsible for this patient's pain?

. Interleukin-1 (IL-1)
. Tumor Necrosis Factor-alpha (TNF-alpha)
. Prostaglandin E2 (PGE2)
. Substance P
. Histamine

Correct Answer & Explanation

. Prostaglandin E2 (PGE2)

Explanation

Osteoid osteoma nidus cells produce high levels of Prostaglandin E2, which causes the characteristic night pain. This is the mechanism by which NSAIDs provide rapid and effective pain relief.

Question 177

Topic: Bone Tumors

A 35-year-old male presents with chronic, insidious nocturnal pain in his long finger, which is partially relieved by over-the-counter NSAIDs. Initial radiographs of the hand were reported as normal. Due to persistent symptoms, a dedicated high-resolution imaging study of the digit is performed. If the suspected diagnosis is an osteoid osteoma of the phalanx, which of the following imaging findings would be most characteristic?

. A. A well-demarcated mass that is hypointense on T1-weighted imaging and markedly hyperintense on T2-weighted imaging with avid gadolinium enhancement.
. B. A disorganized mass of regenerating nerve fibers within scar tissue, typically hypoechoic on ultrasound.
. C. A lucent nidus with surrounding reactive bony sclerosis, often visible on targeted radiographs or CT.
. D. Diffuse soft tissue edema and periarticular osteopenia, consistent with early Complex Regional Pain Syndrome (CRPS).
. E. A subungual hypoechoic lesion with internal vascularity on high-resolution ultrasound.

Correct Answer & Explanation

. C. A lucent nidus with surrounding reactive bony sclerosis, often visible on targeted radiographs or CT.

Explanation

Correct Answer: CThe patient's symptoms—insidious, nocturnal pain relieved by NSAIDs—are highly characteristic of an osteoid osteoma. The case states that osteoid osteomas, while less common in the phalanges, can present this way and that their small size and typical lucent nidus can be overlooked on initial radiographs. The pathophysiology involves prostaglandin production by the nidus, causing pain and adjacent bony sclerosis. Therefore, the most characteristic imaging finding for an osteoid osteoma is a lucent nidus with surrounding reactive bony sclerosis (Option C).Option A describes the typical MRI findings for a glomus tumor. Option B describes a digital neuroma. Option D describes findings associated with CRPS. Option E describes findings that might be seen with a glomus tumor or other soft tissue lesions on ultrasound, but not specifically an osteoid osteoma.

Question 178

Topic: Bone Tumors

A 15-year-old boy presents with progressive distal thigh pain. Radiographs reveal a metaphyseal, poorly marginated, bone-forming lesion in the distal femur with a periosteal "sunburst" reaction and Codman's triangle. What is the standard of care for treating this primary malignancy?

. Wide surgical resection alone
. Neoadjuvant chemotherapy followed by wide resection and adjuvant chemotherapy
. Radiation therapy alone
. Wide resection followed by adjuvant radiation therapy
. Amputation as the sole treatment modality

Correct Answer & Explanation

. Neoadjuvant chemotherapy followed by wide resection and adjuvant chemotherapy

Explanation

The clinical and radiographic findings describe an osteosarcoma. The standard, most effective treatment protocol involves neoadjuvant chemotherapy, surgical resection with wide margins, and post-operative adjuvant chemotherapy.

Question 179

Topic: Bone Tumors

A 12-year-old boy presents with a painless, firm mass on the medial aspect of his distal femur. Plain radiographs are obtained. Which specific feature on the X-ray confirms the diagnosis of an osteochondroma and differentiates it from other surface lesions?

. A 'sunburst' periosteal reaction
. A lytic lesion with a sclerotic rim
. Continuity of the cortex and medullary bone of the lesion with the parent bone
. A purely cartilaginous mass
. Presence of internal calcifications

Correct Answer & Explanation

. Continuity of the cortex and medullary bone of the lesion with the parent bone

Explanation

Correct Answer: CThe hallmark radiographic feature of an osteochondroma is the continuity of the cortical and medullary bone of the exostosis with that of the underlying parent bone. This is crucial for differentiation. 'Sunburst' reaction suggests osteosarcoma. Lytic lesions with sclerotic rims are seen in osteoid osteoma. A purely cartilaginous mass is not typical for an osteochondroma, which is osteocartilaginous. Internal calcifications can be seen in various cartilaginous lesions.

Question 180

Topic: Bone Tumors

A 13-year-old female presents with a painful osteochondroma of the distal femur that impinges on the vastus medialis muscle during knee flexion, causing significant functional limitation. Which of the following is the most appropriate treatment?

. Physical therapy to improve flexibility
. NSAIDs and activity modification
. Surgical excision of the osteochondroma
. Steroid injection into the lesion
. Observation until skeletal maturity

Correct Answer & Explanation

. Surgical excision of the osteochondroma

Explanation

Correct Answer: CWhen an osteochondroma causes mechanical symptoms such as muscle impingement and pain during movement, surgical excision is the definitive treatment. Conservative measures like physical therapy, NSAIDs, or steroid injections are unlikely to resolve mechanical impingement. Observation would allow symptoms to persist or worsen. Surgical excision relieves the mechanical obstruction.

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