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 181
Topic: Bone Tumors
A 19-year-old runner presents with night pain in the thigh that dramatically improves with ibuprofen. Imaging reveals a 1 cm radiolucent nidus surrounded by thick cortical sclerosis. If conservative management fails, what is the preferred definitive treatment?
Correct Answer & Explanation
. CT-guided radiofrequency ablation (RFA)
Explanation
The presentation is classic for an osteoid osteoma. If medical management with NSAIDs is insufficient or poorly tolerated, minimally invasive CT-guided radiofrequency ablation (RFA) is the definitive treatment of choice.
Question 182
Topic: Bone Tumors
A 70-year-old man presents with a pathologic humeral fracture. A skeletal survey reveals multiple "punched-out" lytic lesions, and labs confirm multiple myeloma. Which imaging modality is most critical for detecting impending spinal cord compression in this patient?
Correct Answer & Explanation
. Total body MRI
Explanation
In multiple myeloma, a bone scan is notoriously falsely negative (cold) due to purely osteoclastic activity without osteoblastic repair. Total body MRI is the gold standard for assessing marrow involvement and impending spinal cord compression.
Question 183
Topic: Bone Tumors
A 14-year-old girl presents with an eccentric, expansile, lytic lesion in the proximal tibia metaphysis after a fall. MRI demonstrates multiple fluid-fluid levels. What is the underlying genetic abnormality commonly associated with the primary form of this lesion?
Correct Answer & Explanation
. USP6 gene rearrangement
Explanation
Primary aneurysmal bone cysts (ABCs) are driven by a true neoplastic process, most frequently characterized by a t(16;17) translocation that causes upregulation of the USP6 gene.
Question 184
Topic: Bone Tumors
A 15-year-old boy presents with severe thigh pain primarily at night, which is relieved significantly by ibuprofen. Radiographs and the provided imaging demonstrate a small radiolucent nidus surrounded by dense reactive sclerosis in the proximal femur.
What is the most appropriate definitive management if non-operative measures fail?
Correct Answer & Explanation
. Radiofrequency ablation (RFA)
Explanation
The clinical presentation and imaging are classic for an osteoid osteoma. If conservative management with NSAIDs fails, CT-guided radiofrequency ablation (RFA) is the minimally invasive treatment of choice with high success rates.
Question 185
Topic: Bone Tumors
A 55-year-old male is diagnosed with a grade 2 conventional chondrosarcoma of the proximal femur. Which of the following is the most appropriate definitive treatment?
Correct Answer & Explanation
. Wide surgical excision alone
Explanation
Conventional chondrosarcomas are generally resistant to both chemotherapy and radiation. The standard of care for intermediate to high-grade (grade 2 and 3) chondrosarcoma is wide surgical excision with negative margins.
Question 186
Topic: Bone Tumors
A 10-year-old girl is evaluated for precocious puberty, café-au-lait macules with irregular borders (coast of Maine), and multiple lytic bone lesions showing a "ground-glass" appearance on radiographs. What is the underlying genetic mutation responsible for this syndrome?
Correct Answer & Explanation
. GNAS1 gene mutation
Explanation
The clinical triad describes McCune-Albright syndrome, which is associated with polyostotic fibrous dysplasia. It is caused by an activating post-zygotic somatic mutation in the GNAS1 gene.
Question 187
Topic: Bone Tumors
A 65-year-old male presents with back pain, anemia, hypercalcemia, and elevated creatinine. Radiographs show multiple punched-out lytic lesions in the skull and spine. Which of the following imaging modalities is LEAST likely to accurately reflect the extent of his skeletal disease?
Correct Answer & Explanation
. Technetium-99m bone scan
Explanation
The patient's presentation is classic for multiple myeloma. Technetium-99m bone scans rely on osteoblastic activity, which is typically suppressed in myeloma lesions, frequently resulting in false-negative or cold scans.
Question 188
Topic: Bone Tumors
A 12-year-old male presents with chronic knee pain and swelling. Radiographs show an expansile, eccentric lytic lesion in the metaphysis of the distal femur with a thin cortical shell and a 'soap bubble' appearance. MRI reveals multiple fluid-fluid levels within the lesion. What is the most likely diagnosis?
Correct Answer & Explanation
. Aneurysmal Bone Cyst (ABC)
Explanation
Correct Answer: DThe clinical presentation of an expansile, eccentric lytic lesion with a 'soap bubble' appearance on X-ray, combined with the classic MRI finding of fluid-fluid levels, is highly characteristic of an Aneurysmal Bone Cyst (ABC). While Telangiectatic Osteosarcoma can also present with fluid-fluid levels and lytic destruction, ABCs are typically benign and occur in a younger age group, making ABC the most likely primary diagnosis given the typical presentation. Unicameral Bone Cysts are usually centrally located, do not typically have fluid-fluid levels, and are often asymptomatic until fracture. Giant Cell Tumors are typically epiphyseal and occur in skeletally mature individuals. Chondroblastomas are also epiphyseal but have a chondroid matrix.
Question 189
Topic: Bone Tumors
A patient undergoes selective arterial embolization for a large, inaccessible Aneurysmal Bone Cyst in the sacrum. What is the primary mechanism by which embolization achieves its therapeutic effect?
Correct Answer & Explanation
. Ischemic necrosis of the cyst wall due to reduced blood supply.
Explanation
Correct Answer: BSelective arterial embolization primarily works by cutting off the blood supply to the highly vascularized Aneurysmal Bone Cyst, leading to ischemic necrosis of the cyst wall and eventual thrombosis of the vascular channels. This can cause the lesion to shrink, become less painful, and sometimes resolve completely, especially in inaccessible locations or as a pre-operative measure to reduce intraoperative bleeding. The embolizing agents are not directly toxic to bone cells in a therapeutic manner; their effect is vascular occlusion.
Question 190
Topic: Bone Tumors
Which of the following pathognomonic radiographic signs is most characteristic of the advancing osteolytic wedge seen in the long bones of patients with Paget's disease?
Correct Answer & Explanation
. Blade of grass sign
Explanation
The "blade of grass" or "flame" sign represents the advancing V-shaped radiolucent edge of osteolysis in the long bones during the early lytic phase of Paget's disease.
Question 191
Topic: Bone Tumors
A 6-year-old boy presents with a growing mass near his ankle. Clinical examination reveals an osteochondroma arising from the distal tibia. His parents are concerned about its impact on future growth. What is the most common growth disturbance associated with lower extremity osteochondromas in children?
Correct Answer & Explanation
. Progressive varus or valgus deformity
Explanation
Correct Answer: CThe most common growth disturbance associated with lower extremity osteochondromas, particularly in the distal tibia or fibula, is progressive angular deformity, often genu valgum or varus, and limb length discrepancy. This occurs due to asymmetric growth disturbances at the physis. While limb length discrepancy can occur, angular deformity is explicitly stated as common. Overgrowth is rare. Pes cavus and AVN are not typical complications.
Question 192
Topic: Bone Tumors
A 35-year-old male with a history of multiple hereditary exostoses presents with a rapidly enlarging mass on his proximal femur and increasing pain. MRI demonstrates an osteochondroma with a cartilage cap thickness of 2.5 cm. What is the most likely diagnosis?
Correct Answer & Explanation
. Secondary chondrosarcoma
Explanation
Malignant transformation of an osteochondroma to a secondary chondrosarcoma is rare but should be suspected when the cartilage cap exceeds 2 cm in an adult, or if the lesion grows post-skeletal maturity. The risk is higher in patients with multiple hereditary exostoses.
Question 193
Topic: Bone Tumors
A 12-year-old child with Multiple Hereditary Exostoses (MHE) presents with increasing forearm deformity. Radiographs demonstrate the classic Masada Type I deformity. Which of the following is the hallmark radiographic feature of this specific forearm deformity?
Correct Answer & Explanation
. Relative shortening of the ulna with bowing of the radius
Explanation
The classic forearm deformity in MHE (Masada Type I) is characterized by relative shortening of the ulna due to distal ulnar osteochondromas. This tethering effect leads to secondary bowing of the radius and ulnar deviation of the carpus.
Question 194
Topic: Bone Tumors
A 16-year-old male presents with a painful, firm nodule beneath the nail bed of his great toe. Radiographs demonstrate an exophytic bony mass projecting from the dorsal aspect of the distal phalanx. Histology reveals a cartilage cap, but imaging shows no medullary continuity with the host bone. What is the diagnosis?
Correct Answer & Explanation
. Subungual exostosis
Explanation
A subungual exostosis presents as a painful mass under the nail bed. Unlike a true osteochondroma, it lacks continuity with the medullary canal of the underlying bone and is considered a reactive lesion rather than a true neoplasm.
Question 195
Topic: Bone Tumors
A 14-year-old boy presents with a symptomatic pedunculated osteochondroma on the distal medial femur causing snapping of the pes anserinus tendons. Which of the following is the most critical technical principle when excising this lesion to prevent recurrence?
Correct Answer & Explanation
. Excision of the entire cartilage cap and overlying perichondrium
Explanation
Recurrence of an osteochondroma after surgical excision is rare but typically occurs due to incomplete removal of the cartilage cap or the overlying perichondrium. Complete excision at the base of the stalk, ensuring the entire cartilage cap and perichondrium are removed, is essential.
Question 196
Topic: Bone Tumors
Which chemotherapy agent used in osteosarcoma treatment is associated with the risk of cardiotoxicity, particularly cumulative dose-dependent cardiomyopathy?
Correct Answer & Explanation
. Doxorubicin
Explanation
Correct Answer: DDoxorubicin (Adriamycin) is a highly effective anthracycline antibiotic used in osteosarcoma regimens, but its main dose-limiting toxicity is cumulative, dose-dependent cardiotoxicity, leading to dilated cardiomyopathy and congestive heart failure. Lifelong monitoring of cardiac function is required, and the cumulative dose must be carefully managed. Methotrexate causes renal toxicity and mucositis. Cisplatin causes ototoxicity, nephrotoxicity, and neurotoxicity. Ifosfamide can cause hemorrhagic cystitis (prevented with Mesna) and neurotoxicity. Etoposide is associated with myelosuppression and mucositis.
Question 197
Topic: Bone Tumors
A 10-year-old girl with a known Non-Ossifying Fibroma (NOF) in the distal tibia is scheduled for a follow-up radiograph in 6 months. Her initial radiograph is shown. What radiographic finding would indicate the lesion is entering its 'healing' or 'latent' phase?
Correct Answer & Explanation
. Increased central sclerosis and gradual filling in of the lucency.
Explanation
Correct Answer: CThe 'healing' or 'latent' phase of a Non-Ossifying Fibroma is characterized by a gradual increase in central sclerosis, with the lesion becoming denser and eventually filling in with normal bone. The lesion typically shrinks, and the lucent area is replaced by opaque bone. Increased size and cortical thinning (option A) would suggest continued activity or growth. Development of new periosteal reaction (option B) or soft tissue mass formation (option E) would be atypical for a healing NOF and raise concern for other pathologies or complications like fracture. Fluid-fluid levels (option D) are characteristic of aneurysmal bone cysts, not NOFs.
Question 198
Topic: Bone Tumors
A 12-year-old boy presents with a large, expansile, lytic metaphyseal lesion in the proximal tibia. An MRI is performed to further characterize the lesion. Which of the following features on the MRI would *strongly suggest* a diagnosis *other than* Non-Ossifying Fibroma?
Correct Answer & Explanation
. Fluid-fluid levels on T2-weighted MRI.
Explanation
Correct Answer: CFluid-fluid levels on MRI are highly characteristic of an Aneurysmal Bone Cyst (ABC) and are typically not seen in a Non-Ossifying Fibroma. While NOFs can be eccentric (option A), have a sclerotic rim (option B), appear multiloculated (option D), and cause cortical thinning (option E), the presence of fluid-fluid levels would strongly point away from an NOF and towards an ABC or other cystic/hemorrhagic lesion. Differentiating NOF from ABC is crucial as their management strategies can differ, especially for large or symptomatic lesions.
Question 199
Topic: Bone Tumors
A 7-year-old child presents with a well-defined, asymptomatic lesion on a radiograph of the distal femur. The lesion is cortical-based, eccentrically located, and appears lucent with a sclerotic rim, measuring 1.5 cm in its greatest dimension. Which term is most accurately used to describe this small, purely cortical lesion with these features?
Correct Answer & Explanation
. Fibrous Cortical Defect
Explanation
Correct Answer: CA small, purely cortical, asymptomatic non-ossifying fibroma is often referred to as a fibrous cortical defect (FCD). FCDs are essentially smaller versions of NOFs, sharing the same histological and radiographic characteristics, but are typically less than 2-3 cm and confined to the cortex. They are very common, found in up to 30-40% of children. Unicameral bone cysts and aneurysmal bone cysts are typically medullary and often larger. Osteoid osteoma has a characteristic nidus and often causes night pain relieved by NSAIDs. Chondromyxoid fibroma is a distinct cartilaginous tumor.
Question 200
Topic: Bone Tumors
A 13-year-old boy has an asymptomatic 5 cm Non-Ossifying Fibroma of the proximal tibia, incidentally discovered on radiographs. The lesion involves approximately 60% of the cortical circumference, as shown in the image. What is the most critical factor guiding surgical intervention in this case?
Correct Answer & Explanation
. The percentage of cortical involvement by the lesion.
Explanation
Correct Answer: EThe size of the NOF and, more importantly, its involvement of the cortical bone (typically >50% of the cortical diameter or a lesion >2 cm in diameter in a weight-bearing bone) are the most critical factors determining the risk of pathological fracture and, consequently, the need for surgical intervention. A lesion involving 60% of the cortical circumference significantly weakens the bone, placing it at high risk for fracture. While the exact location (option B) is relevant (weight-bearing bones are higher risk), thepercentage of cortical involvementis the direct measure of structural weakening. Patient preference (option A) is considered but not the primary medical factor. Fluid-fluid levels (option C) suggest an ABC, not an NOF. Elevated calcium (option D) is irrelevant for NOF.
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