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10. Pathology and Oncology MCQs

Practice Set 65 of 351

This practice set contains high-yield board review questions covering key concepts in 10. Pathology and Oncology. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 1281

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 1282

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 1283

Topic: 10. Pathology and Oncology

A 21-year-old male undergoes surgical excision of a suspected osteoid osteoma in the L4 lamina. Histopathological examination of the nidus is most likely to reveal which of the following?

. Malignant spindle cells producing osteoid
. Interlacing trabeculae of woven bone rimmed by prominent osteoblasts
. Cartilage-capped bony exostosis
. Sheets of uniform round cells with glycogen-rich cytoplasm
. Multinucleated giant cells in a background of mononuclear stromal cells

Correct Answer & Explanation

. Interlacing trabeculae of woven bone rimmed by prominent osteoblasts

Explanation

The classic histologic appearance of an osteoid osteoma is a sharply demarcated nidus consisting of interlacing trabeculae of osteoid and woven bone, lined by prominent, benign osteoblasts. It lacks the atypical, malignant cells seen in osteosarcoma.

Question 1284

Topic: 10. Pathology and Oncology

Both osteoid osteomas and osteoblastomas are benign bone-forming tumors that commonly affect the posterior elements of the spine. Which of the following clinical or radiographic features most reliably differentiates an osteoblastoma from an osteoid osteoma?

. Presence of a sclerotic border
. Location in the vertebral body rather than pedicle
. Size of the nidus greater than 2.0 cm
. Dramatic relief of pain with NSAIDs
. Histologic presence of woven bone

Correct Answer & Explanation

. Size of the nidus greater than 2.0 cm

Explanation

Osteoblastomas are distinguished from osteoid osteomas primarily by size, with a nidus generally larger than 1.5 to 2.0 cm. They are also less likely to have profound reactive sclerosis and the classic, dramatic pain relief with NSAIDs.

Question 1285

Topic: 10. Pathology and Oncology

A 24-year-old male with a documented osteoid osteoma of the T11 pedicle asks why his pain is uniquely worse at night and responsive to aspirin. This symptom profile is primarily mediated by local tumor production of which of the following substances?

. Interleukin-1
. Tumor necrosis factor-alpha
. Prostaglandin E2
. Substance P
. Histamine

Correct Answer & Explanation

. Prostaglandin E2

Explanation

Osteoid osteomas secrete high levels of prostaglandins, particularly Prostaglandin E2 (PGE2), which mediates vasodilation and severe pain. This high local concentration of PGE2 explains the characteristic dramatic relief provided by NSAIDs.

Question 1286

Topic: 10. Pathology and Oncology

A 14-year-old girl is diagnosed with a spinal osteoid osteoma causing a secondary painful scoliosis. The lesion is successfully treated with percutaneous radiofrequency ablation. What is the expected outcome of her scoliosis following definitive treatment?

. The curve will rapidly progress and require spinal fusion
. The curve will typically resolve spontaneously if present for less than 15 months
. The curve will become a structural curve that necessitates immediate bracing
. The curve will reverse its concavity over the next 6 months
. The curve will remain static but the pain will resolve completely

Correct Answer & Explanation

. The curve will typically resolve spontaneously if present for less than 15 months

Explanation

Scoliosis secondary to an osteoid osteoma is typically a non-structural, protective muscle spasm. If the tumor is completely excised or ablated before structural changes occur (usually less than 15 months), the curve typically resolves spontaneously.

Question 1287

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 1288

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 1289

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 1290

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 1291

Topic: 10. Pathology and Oncology

The intense night pain classically associated with an osteoid osteoma is mediated by high local concentrations of which of the following substances?

. Tumor necrosis factor-alpha (TNF-a)
. Interleukin-6 (IL-6)
. Prostaglandin E2 (PGE2)
. Substance P
. Bradykinin

Correct Answer & Explanation

. Prostaglandin E2 (PGE2)

Explanation

Osteoid osteomas secrete high levels of Prostaglandin E2 (PGE2), which mediates the characteristic severe, throbbing night pain. This pathophysiology explains why these lesions are dramatically responsive to NSAIDs.

Question 1292

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 1293

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 1294

Topic: 10. Pathology and Oncology

A 10-year-old child undergoes radiofrequency ablation for an osteoid osteoma of the L5 vertebral body. Compared to osteoid osteomas in the appendicular skeleton, those located in the spine have a higher association with which of the following?

. Malignant transformation to osteosarcoma
. Neurologic deficit prior to treatment
. Painful non-structural scoliosis
. Pathologic vertebral burst fractures
. Multiple discrete nidi within the same bone

Correct Answer & Explanation

. Painful non-structural scoliosis

Explanation

Spinal osteoid osteomas uniquely cause a painful, non-structural scoliosis due to asymmetric muscle spasm. Malignant transformation does not occur, and gross neurologic deficits are rare unless there is significant epidural compression.

Question 1295

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 1296

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 1297

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 1298

Topic: 10. Pathology and Oncology

A 50-year-old patient presents with a 34° Fixed Flexion Deformity (FFD) of the knee following extensive radiation therapy for a distal femoral sarcoma. Radiographic analysis reveals a 14° femoral procurvatum and a 12° tibial procurvatum. The calculated soft tissue contracture is 8°. Given the patient's history of radiation, which of the following is the MOST appropriate strategy for addressing the soft tissue component of the deformity?

. An aggressive open posterior capsular release to achieve immediate correction.
. A staged approach involving initial bony correction followed by a delayed open soft tissue release once tissues have healed.
. Gradual distraction of the joint using an external fixator to stretch the soft tissues.
. High-dose corticosteroid injections into the posterior capsule to reduce fibrosis before open release.
. Ignoring the soft tissue component, as bony correction will indirectly stretch the contracted tissues sufficiently.

Correct Answer & Explanation

. Gradual distraction of the joint using an external fixator to stretch the soft tissues.

Explanation

Correct Answer: CThe case specifically addresses 'The Irradiated or Severely Scarred Knee,' stating that 'Radiation creates a profoundly hostile soft-tissue envelope characterized by severe microvascular damage, profound fibrosis, and chronic tissue hypoxia.' It explicitly warns that 'attempting an open posterior soft tissue release is fraught with extreme peril, carrying an unacceptably high risk of catastrophic wound breakdown, deep tissue necrosis, and devastating neurovascular injury.'For such cases, the implied and generally accepted strategy isgradual distraction(often with an external fixator) to safely stretch the contracted soft tissues over time, minimizing the risk of wound complications and neurovascular injury. The case example for post-radiation contracture implies this approach by stating the need to address the soft tissue component without suggesting an open release.Options A and B are contraindicated due to the high risk of complications in irradiated tissue. Option D is not a standard or effective treatment for severe fibrotic contractures. Option E is incorrect, as ignoring the soft tissue component will lead to joint incongruity and recurrence of the FFD, as discussed in the 'Flawed Alternative Strategy' section.

Question 1299

Topic: 10. Pathology and Oncology

A 4-year-old child presents with a 3 cm LLD and unilateral limb overgrowth. Examination reveals classic signs of isolated hemihypertrophy. Due to the association with Beckwith-Wiedemann syndrome, this patient requires routine screening with abdominal ultrasound until age 8 for which of the following?

. Neuroblastoma
. Hepatoblastoma and Wilms tumor
. Pheochromocytoma
. Renal cell carcinoma
. Adrenal cortical adenoma

Correct Answer & Explanation

. Hepatoblastoma and Wilms tumor

Explanation

Idiopathic hemihypertrophy and Beckwith-Wiedemann syndrome carry a high risk of embryonal tumors, predominantly Wilms tumor (nephroblastoma) and hepatoblastoma. Screening protocols require abdominal ultrasound every 3 months until age 8.

Question 1300

Topic: 10. Pathology and Oncology

A 62-year-old male presents with a slowly enlarging, painless mass in his right posterior thigh, first noticed 18 months prior, with rapid growth in the last 6 months. Physical examination reveals a deep-seated, firm-to-rubbery, 10x8 cm mass with severely limited mobility. Distal neurovascular status is intact. Given these initial findings, which of the following characteristics is the *most* concerning for a soft tissue sarcoma?

. A. The patient's age of 62 years.
. B. The mass being painless.
. C. The insidious onset 18 months prior.
. D. The deep subfascial location and recent rapid growth.
. E. Intact distal neurovascular status.

Correct Answer & Explanation

. D. The deep subfascial location and recent rapid growth.

Explanation

Correct Answer: DThe most concerning characteristic for a soft tissue sarcoma in this presentation is thedeep subfascial location and recent rapid growth. The case explicitly states, 'The presentation of a deep, painless, enlarging soft tissue mass greater than 5 centimeters in an adult must be considered a soft tissue sarcoma until proven otherwise. The historical details, specifically the deep subfascial location and the recent acceleration in growth, raise immediate suspicion for a malignant process.' Deep location, size greater than 5 cm, and rapid growth are classic 'red flags' for malignancy.Option A (The patient's age of 62 years): While soft tissue sarcomas are more common in older adults, age alone is not the most concerning feature compared to tumor characteristics. Sarcomas can occur at any age.Option B (The mass being painless): Painless masses are often dismissed, but many sarcomas are indeed painless, especially in their early stages. Pain is a late symptom, often indicating nerve involvement or rapid expansion, but its absence does not rule out malignancy.Option C (The insidious onset 18 months prior): The insidious onset is common for many soft tissue masses, both benign and malignant. Thechangein growth pattern (rapid acceleration) is more concerning than the initial slow growth.Option E (Intact distal neurovascular status): Intact neurovascular status is a reassuring sign regarding limb function but does not diminish the suspicion of malignancy. Sarcomas can grow to a large size by displacing neurovascular structures before causing deficits.

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