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Bone Tumors MCQs

Practice Set 12 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 221

Topic: Bone Tumors

A 28-year-old patient is undergoing open surgical excision of an osteoid osteoma located deep within the L5 pedicle, close to the traversing S1 nerve root. The surgeon has exposed the posterior elements. Which intraoperative localization technique offers the highest accuracy for guiding the resection to the nidus while minimizing bone removal and risk to neural structures?

. Intraoperative fluoroscopy (C-arm) alone.
. Visual and tactile identification of the nidus.
. Pre-operative CT-guided wire localization.
. Intraoperative O-arm or navigation system.
. Gamma probe detection after Technetium-99m injection.

Correct Answer & Explanation

. Intraoperative O-arm or navigation system.

Explanation

Correct Answer: DExplanation:The case emphasizes the criticality of intraoperative nidus localization, especially for deep or complex lesions. It states: 'Advanced Navigation (O-arm / Intraoperative CT): Increasingly utilized for complex spinal cases. Fusion of pre-operative CT data with intraoperative imaging allows for real-time, highly accurate 3D guidance to the nidus, minimizing dissection and improving resection accuracy.' For a deep pedicle lesion close to a nerve root, this 3D real-time guidance is superior for precision and safety.Option A (Intraoperative fluoroscopy (C-arm) alone):Fluoroscopy is essential for verifying the correct spinal level but provides only 2D images and is less precise for deep, 3D localization of a small nidus within a pedicle.Option B (Visual and tactile identification of the nidus):The case states this is 'unreliable for definitive localization,' especially for deep lesions.Option C (Pre-operative CT-guided wire localization):While useful for very small or deeply situated nidi, it is a pre-operative measure. The wire can migrate, and intraoperative confirmation with real-time 3D imaging (like O-arm) offers superior dynamic guidance during the actual resection.Option E (Gamma probe detection after Technetium-99m injection):The case mentions this as 'less common than CT-guided techniques in spinal surgery' and primarily identifies areas of increased metabolic activity, lacking the precise anatomical detail for guiding resection in a delicate area like the pedicle.

Question 222

Topic: Bone Tumors

A 19-year-old female presents with axial low back pain, particularly bothersome at night and remarkably relieved by ibuprofen. Initial radiographs are equivocal. Which of the following imaging modalities is considered the gold standard for identifying the exact location of the nidus of a suspected spinal osteoid osteoma?

. Technetium-99m bone scan
. Non-contrast MRI
. Thin-slice CT scan
. PET scan
. Ultrasound

Correct Answer & Explanation

. Thin-slice CT scan

Explanation

A thin-slice CT scan is the best imaging modality to precisely localize the central radiolucent nidus surrounded by reactive sclerosis characteristic of an osteoid osteoma. MRI often overestimates the reactive edema and can obscure the small nidus.

Question 223

Topic: Bone Tumors

A 28-year-old male presents with chronic back pain and stiffness. Imaging reveals a 2.5 cm radiolucent lesion in the L3 posterior elements with mild surrounding sclerosis. The patient reports his pain is dull, continuous, and only mildly relieved by ibuprofen. What is the most likely diagnosis?

. Osteoid osteoma
. Aneurysmal bone cyst
. Osteoblastoma
. Ewing sarcoma
. Multiple myeloma

Correct Answer & Explanation

. Osteoblastoma

Explanation

The lesion is larger than 1.5-2.0 cm and does not present with the classic, dramatic nocturnal pain responsive to NSAIDs. These features distinguish osteoblastoma from osteoid osteoma, despite similar predilections for the posterior elements of the spine.

Question 224

Topic: Bone Tumors

A 13-year-old girl is diagnosed with a spinal osteoid osteoma that has caused a painful secondary scoliosis. Her symptoms began 8 months ago. If she undergoes successful radiofrequency ablation (RFA) of the nidus, what is the most likely natural history of her spinal deformity?

. The curve will progress and inevitably require spinal fusion.
. The curve will spontaneously resolve over several months.
. The curve will become rigid and require long-term bracing.
. The curve will resolve only if anterior tethering is performed.
. The curve will remain static but painless.

Correct Answer & Explanation

. The curve will spontaneously resolve over several months.

Explanation

Scoliosis secondary to an osteoid osteoma is initially flexible and driven by muscle spasm. If the lesion is successfully treated (excised or ablated) within 15 months of symptom onset, the scoliotic curve typically resolves spontaneously.

Question 225

Topic: Bone Tumors

A 22-year-old male presents with chronic axial back pain. Imaging reveals a radiolucent lesion in the posterior elements of L3 with surrounding sclerosis. The nidus measures 2.4 cm in diameter. Histologically, the lesion shows interlacing trabeculae of woven bone. What is the most likely diagnosis?

. Osteoid osteoma
. Osteoblastoma
. Aneurysmal bone cyst
. Osteosarcoma
. Chondroblastoma

Correct Answer & Explanation

. Osteoblastoma

Explanation

Osteoid osteoma and osteoblastoma have virtually identical histologic appearances. They are differentiated primarily by size, with a nidus greater than 1.5 cm (or 2.0 cm in some texts) classifying the lesion as an osteoblastoma.

Question 226

Topic: Bone Tumors

An 18-year-old male is diagnosed with an osteoid osteoma of the L4 pedicle. Advanced imaging reveals the nidus is located 4 mm from the L4 exiting nerve root. What is the most appropriate definitive management?

. Radiofrequency ablation (RFA)
. Surgical excision
. Observation with bracing
. Radiation therapy
. Chemotherapy

Correct Answer & Explanation

. Surgical excision

Explanation

While RFA is the standard of care for most osteoid osteomas, it is generally contraindicated when the lesion is within 1 cm of critical neural elements due to the risk of thermal injury. Surgical excision is preferred in this scenario.

Question 227

Topic: Bone Tumors

A 15-year-old girl has had painful scoliosis for 10 months due to an osteoid osteoma located in the L3 lamina. If the patient undergoes successful surgical resection of the lesion today, what is the most likely natural history of her scoliotic curve?

. The curve will rapidly progress and require instrumented fusion
. The curve will spontaneously resolve over time
. The curve will reverse its concavity
. The curve will remain static but rigid
. The curve will degenerate into a double major structural deformity

Correct Answer & Explanation

. The curve will spontaneously resolve over time

Explanation

Scoliosis secondary to an osteoid osteoma is non-structural and typically resolves spontaneously if the lesion is successfully treated within 15 to 18 months of symptom onset. If left untreated longer, it may become a permanent structural deformity.

Question 228

Topic: Bone Tumors

A 22-year-old male presents with persistent back pain. Radiographs demonstrate a sclerotic lesion in the T12 pedicle. Which of the following imaging characteristics reliably differentiates an osteoid osteoma from an osteoblastoma?

. Osteoid osteomas have a radiolucent nidus greater than 2.0 cm
. Osteoid osteomas have a radiolucent nidus less than 1.5 cm
. Osteoblastomas are purely sclerotic without a nidus
. Osteoblastomas only occur in the anterior vertebral body
. Osteoid osteomas lack reactive surrounding sclerosis

Correct Answer & Explanation

. Osteoid osteomas have a radiolucent nidus less than 1.5 cm

Explanation

By definition, the radiolucent nidus of an osteoid osteoma is less than 1.5 cm in diameter, whereas osteoblastomas are distinguished by a size greater than 1.5 to 2.0 cm. Both can affect the posterior elements of the spine.

Question 229

Topic: Bone Tumors

The profound night pain associated with a spinal osteoid osteoma is primarily mediated by which of the following mechanisms?

. Direct compression of the exiting nerve root by the nidus
. High levels of prostaglandin E2 produced by the nidus
. Microfractures of the surrounding sclerotic bone
. Release of histamine from intralesional mast cells
. Ischemia secondary to tumor angiogenesis

Correct Answer & Explanation

. High levels of prostaglandin E2 produced by the nidus

Explanation

Osteoid osteomas produce exceptionally high levels of prostaglandin E2 due to increased COX-2 expression. This local PGE2 production mediates the severe night pain, which is classically relieved by NSAIDs.

Question 230

Topic: Bone Tumors

A 19-year-old female is diagnosed with an osteoid osteoma of the L4 pedicle. A CT scan

reveals the nidus is located 6 mm from the adjacent exiting nerve root. Which of the following is the most appropriate surgical treatment?

. CT-guided radiofrequency ablation (RFA)
. Curettage via a posterior approach
. En bloc resection with wide margins
. Radiation therapy
. Cryoablation

Correct Answer & Explanation

. Curettage via a posterior approach

Explanation

Radiofrequency ablation (RFA) is generally contraindicated when the nidus is located within 1 cm (10 mm) of neural elements or the dura due to the risk of thermal injury. Surgical excision (curettage) is the treatment of choice in these cases.

Question 231

Topic: Bone Tumors

A 16-year-old male complains of severe, progressively worsening low back pain at night. Initial radiographs are unremarkable. An MRI is ordered and shows extensive bone marrow edema in the L3 pedicle and pars interarticularis, raising suspicion for a malignancy or infection. What is the most appropriate next imaging step to confirm the suspected diagnosis of osteoid osteoma?

. Bone scintigraphy (Tc-99m)
. Positron emission tomography (PET) scan
. Thin-slice computed tomography (CT)
. Repeat MRI with gadolinium contrast
. Ultrasound of the paraspinal musculature

Correct Answer & Explanation

. Thin-slice computed tomography (CT)

Explanation

Thin-slice CT is the imaging modality of choice for identifying the characteristic radiolucent nidus of an osteoid osteoma. MRI often overestimates the lesion due to extensive surrounding bone marrow edema, frequently leading to misdiagnosis as a malignancy or infection.

Question 232

Topic: Bone Tumors
During distraction osteogenesis, if the rate of distraction is too rapid (e.g., >2.0 mm per day), what is the most likely complication affecting the regenerate bone?
. Premature consolidation of the osteotomy site.
. Delayed consolidation or nonunion of the regenerate.
. Excessive periosteal hypertrophy.
. Hypervascularity leading to arteriovenous fistula formation.
. Development of a symptomatic osteochondroma.

Correct Answer & Explanation

. Delayed consolidation or nonunion of the regenerate.

Explanation

The optimal rate for distraction osteogenesis is 1 mm per day. Rates exceeding this frequently lead to poor regenerate formation, delayed consolidation, or nonunion.

Question 233

Topic: Bone Tumors
An otherwise healthy 33-year-old man who works in construction reports a 3-month history of knee pain. Radiographs are shown in Figures 9a and 9b. An axial T1-weighted MRI scan with contrast, an angiogram, and histologies are shown in Figures 9c through 9f. What is the most likely diagnosis?
. Conventional osteosarcoma
. Myositis ossificans
. Osteochondroma
. Parosteal osteosarcoma
. Dedifferentiated parosteal osteosarcoma

Correct Answer & Explanation

. Dedifferentiated parosteal osteosarcoma

Explanation

DISCUSSION: Dedifferentiated parosteal osteosarcoma designates high-grade transformation of conventional low-grade parosteal osteosarcoma. Unlike conventional parosteal osteosarcoma, where wide surgical excision alone is considered adequate treatment, patients with dedifferentiated osteosarcoma are treated with neoadjuvant chemotherapy and wide local resection. Recognition of dedifferentiated areas with angiography can localize the area that should be biopsied and thus render an accurate diagnosis. Percutaneous biopsy of hypervascular areas should prompt the administration of chemotherapy and wide local excision to optimize patient outcome. REFERENCES: Sheth DS, Yasko AW, Raymond AK, et al: Conventional and dedifferentiated parosteal osteosarcoma: Diagnosis, treatment, and outcome. Cancer 1996;78:2136-2145. Lewis VO, Gebhardt MC, Springfield DS: Parosteal osteosarcoma of the posterior aspect of the distal part of the femur: Oncological and functional results following a new resection technique. J Bone Joint Surg Am 2000;82:1083-1088.

Question 234

Topic: Bone Tumors
A 27-year-old man has had pain in the right index finger for the past 9 months. The pain is completely relieved with ibuprofen. An AP radiograph and CT scan are shown in Figures 80a and 80b. What is the most likely diagnosis?
. Brodie’s abscess
. Hyperparathyroidism
. Stress fracture
. Enchondroma
. Osteoid osteoma

Correct Answer & Explanation

. Osteoid osteoma

Explanation

DISCUSSION: Osteoid osteoma is a round or oval, well-circumscribed lesion with a radiolucent nidus. A small area of calcification may be present within the center of the nidus. The radiolucent nidus is surrounded by a thick rim of sclerotic bone. These diagnostic features are frequently better seen on CT. An increase in cyclooxygenase activity has been demonstrated within osteoid osteomas, which may explain why aspirin and other nonsteroidal anti-inflammatory drugs classically relieve the pain associated with these lesions. REFERENCES: Kneisl JS, Simon MA: Medical management compared with operative treatment for osteoid-osteoma. J Bone Joint Surg Am 1992;74:179-185. Unni KK: Dahlin’s Bone Tumors: General Aspects and Data on 11,087 Cases, ed 5. Philadelphia, PA, Lippincott-Raven, 1996, pp 121-130.

Question 235

Topic: Bone Tumors
Which of the following is most associated with local recurrence of the lesion seen in the radiograph and MRI scan shown in Figures 27a and 27b?
. Effectiveness of chemotherapy
. Effect of local adjuvant
. Open physes
. Presence of giant cells
. Effectiveness of embolization

Correct Answer & Explanation

. Open physes

Explanation

DISCUSSION: The lesion is an aneurysmal bone cyst. These lesions are known to have a local recurrence rate of 5% to 50%. Young age, open physes, stage, and type of surgical removal and resulting margin have all been shown to affect the recurrence rate. Chemotherapy is not used in the treatment of aneurysmal bone cysts. REFERENCES: Gibbs CP Jr, Hefele MC, Peabody TD, et al: Aneurysmal bone cyst of the extremities: Factors related to local recurrence after curettage with a high-speed burr. J Bone Joint Surg Am 1999;81:1671-1678. Vergel De Dios AM, Bond JR, Shives TC, et al: Aneurysmal bone cyst: A clinicopathologic study of 238 cases. Cancer 1992;69:2921-2931.

Question 236

Topic: Bone Tumors
A 16-year-old girl has had anterior leg pain and a mass for the past 8 months. Figures 2a and 2b show a radiograph and an H & E histologic specimen. Which of the following disorders is believed to be a precursor of this lesion?
. Nonossifying fibroma
. Fibrous dysplasia
. Unicameral bone cyst
. Osteogenesis imperfecta
. Osteofibrous dysplasia

Correct Answer & Explanation

. Osteofibrous dysplasia

Explanation

DISCUSSION: The radiograph and pathology are consistent with adamantinoma. While the mechanism underlying adamantinoma has not been identified, it is believed to be closely related to osteofibrous dysplasia, which may represent a precursor. The other diagnoses are not known to give rise to adamantinoma. REFERENCE: Springfield DS, Rosenberg AE, Mankin HJ, et al: Relationship between osteofibrous dysplasia and adamantinoma. Clin Orthop 1994;309:234-244.

Question 237

Topic: Bone Tumors
What is the most common anatomic location for chondrosarcoma?
. Hand
. Distal femur
. Proximal humerus
. Spine
. Pelvis

Correct Answer & Explanation

. Pelvis

Explanation

The most common anatomic location of chondrosarcoma is the pelvis (30%), followed by the proximal femur (20%). Chondrosarcomas appear in the shoulder girdle in 15% of patients but rarely affect the spine or hands.

Question 238

Topic: Bone Tumors

Primary chondrosarcoma of bone most commonly occurs in which of the following locations?

. Hand
. Knee
. Shoulder
. Spine
. Pelvis

Correct Answer & Explanation

. Hand

Explanation

DISCUSSION: The most common location of chondrosarcoma is the pelvis (30%), followed by the proximal femur (20%) and shoulder girdle (15%).  Chondrosarcoma rarely affects the spine or hand.REFERENCES: Lee FY, Mankin HJ, Fondren G, et al: Chondrosarcoma of bone: An assessment of outcome.  J Bone Joint Surg Am 1999;81:326-338.Simon M, Springfield D, et al: Chondrosarcoma: Surgery for Bone and Soft Tissue Tumors.  Philadelphia, PA, Lippincott Raven, 1998, p 276.

Question 239

Topic: Bone Tumors

A 17-year-old girl who initially presented as a child with multiple skeletal lesions, café-au-lait spots, and precocious puberty now has bone pain. A recent bone scan reveals multiple areas of increased scintigraphic uptake, including bilateral proximal femurs. A radiograph is shown in Figure 19. Besides activity modification, what is the next best line of treatment for decreasing her pain? Review Topic

. Bisphosphonates
. Calcitonin
. Parathyroid hormone
. Vitamin D and calcium
. Methotrexate

Correct Answer & Explanation

. Bisphosphonates

Explanation

McCune-Albright syndrome is the combination of polyostotic fibrous dysplasia, café-au-lait lesions, and endocrine dysfunction. The most common endocrine presentation is precocious development of secondary sexual characteristics. Compared with bone lesions in patients without polyostotic disease, the skeletal lesions in patients with the syndrome tend to be larger, more persistent, and associated with more complications. Bisphosphonate therapy has been shown in several studies to decrease the pain associated with the skeletal lesions of fibrous dysplasia.

Question 240

Topic: Bone Tumors

A 40-year-old man with an acetabular chondrosarcoma has a small soft-tissue mass. Treatment should consist of

. chemotherapy with ifosfamide and doxorubicin hydrochloride.
. external beam radiation.
. wide resection.
. curettage and cementation of the pelvic lesion.
. cemented total hip arthroplasty with acetabular reconstruction.

Correct Answer & Explanation

. chemotherapy with ifosfamide and doxorubicin hydrochloride.

Explanation

DISCUSSION: The treatment of choice for pelvic chondrosarcoma is wide resection via an internal hemipelvectomy.  Chondrosarcoma requires surgical resection for control and does not respond to traditional chemotherapy or external beam radiation.  Hip arthroplasty with acetabular reconstruction and curettage and cementation of the lesion are intralesional procedures that result in a higher incidence of local recurrence of tumor.REFERENCES: Pring M, Weber KL, Unni K, Sim FH: Chondrosarcoma of the pelvis: A review of sixty-four cases.  J Bone Joint Surg Am 2001;83:1630-1642.Sheth DS, Yasko AW, Johnson ME, Ayala AG, Murray JA, Romsdahl MM: Chondrosarcoma of the pelvis: Prognostic factors for 67 patients treated with definitive surgery.  Cancer 1996;78:745-750.

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