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10. Pathology and Oncology MCQs

Practice Set 187 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 3721

Topic: 10. Pathology and Oncology

A 30-year-old male with known Neurofibromatosis Type 1 (NF1) presents with a rapidly enlarging, painful mass in his thigh. Biopsy demonstrates a high mitotic rate, necrosis, and marked nuclear pleomorphism. Which of the following is the most likely precursor lesion for this malignancy?

. Solitary encapsulated schwannoma
. Plexiform neurofibroma
. Cutaneous neurofibroma
. Traumatic neuroma
. Glomus tumor

Correct Answer & Explanation

. Plexiform neurofibroma

Explanation

This patient has developed a Malignant Peripheral Nerve Sheath Tumor (MPNST). In patients with NF1, MPNSTs almost exclusively arise from pre-existing plexiform neurofibromas rather than solitary or cutaneous variants.

Question 3722

Topic: 10. Pathology and Oncology

During surgical exploration of a peripheral nerve tumor, the surgeon notes the mass is encapsulated and located eccentrically, allowing the continuous nerve fascicles to be carefully peeled away from the tumor capsule. What is the recommended surgical management?

. Intralesional curettage
. Marginal enucleation
. Wide local excision
. Segmental nerve resection with grafting
. Epineural repair only

Correct Answer & Explanation

. Marginal enucleation

Explanation

The intraoperative finding of an eccentric, encapsulated tumor that spares the nerve fascicles is characteristic of a schwannoma. The standard treatment is marginal enucleation, preserving the parent nerve.

Question 3723

Topic: 10. Pathology and Oncology

A 25-year-old male presents with a central, fusiform enlargement of the median nerve. Histology reveals spindle cells in a myxoid stroma with "shredded carrot" collagen, and the mass cannot be separated from the nerve fascicles. The mutated gene responsible for this condition normally performs which of the following functions?

. Downregulation of the RAS signaling pathway
. Upregulation of the mTOR pathway
. Downregulation of the p53 tumor suppressor
. Modulation of the actin cytoskeleton via Merlin
. Inhibition of the Wnt/beta-catenin pathway

Correct Answer & Explanation

. Downregulation of the RAS signaling pathway

Explanation

The description is classic for a neurofibroma, associated with NF1. The NF1 gene produces neurofibromin, a GTPase-activating protein that downregulates the RAS signaling pathway.

Question 3724

Topic: 10. Pathology and Oncology

Which of the following describes the characteristic "target sign" frequently observed on T2-weighted MRI of benign peripheral nerve sheath tumors?

. Central low signal intensity with peripheral high signal intensity
. Central high signal intensity with peripheral low signal intensity
. Uniform high signal intensity with a low signal pseudocapsule
. Uniform low signal intensity with surrounding peritumoral edema
. Internal fluid-fluid levels with peripheral enhancement

Correct Answer & Explanation

. Central low signal intensity with peripheral high signal intensity

Explanation

The MRI "target sign" on T2-weighted imaging features central hypointensity (corresponding to dense fibrocollagenous tissue) and peripheral hyperintensity (corresponding to myxoid tissue). It is highly suggestive of benign neurogenic tumors like schwannomas.

Question 3725

Topic: 10. Pathology and Oncology

An 18-year-old female presents with bilateral hearing loss, multiple cutaneous schwannomas, and meningiomas. The defective protein in her underlying condition normally localizes to which of the following cellular areas?

. The nucleus to regulate DNA transcription
. The mitochondrial membrane for oxidative phosphorylation
. The cell membrane-cytoskeleton interface
. The endoplasmic reticulum for protein folding
. The Golgi apparatus for vesicle transport

Correct Answer & Explanation

. The cell membrane-cytoskeleton interface

Explanation

The patient has Neurofibromatosis Type 2 (NF2), caused by a mutation in the NF2 gene on chromosome 22. This gene encodes merlin (schwannomin), a tumor suppressor protein that links actin filaments to cell membrane proteins.

Question 3726

Topic: Soft Tissue Tumors & Metastasis

Immunohistochemical staining is performed on a suspected peripheral nerve sheath tumor to differentiate between a schwannoma and a neurofibroma. Which staining profile most strongly supports a diagnosis of a schwannoma?

. Diffuse, strong S-100 positivity and presence of SOX10
. Patchy, weak S-100 positivity with CD34 positive fibroblasts
. Diffuse Desmin and MyoD1 positivity
. Loss of H3K27me3 expression
. Strong epithelial membrane antigen (EMA) positivity in the core

Correct Answer & Explanation

. Diffuse, strong S-100 positivity and presence of SOX10

Explanation

Schwannomas are composed almost entirely of Schwann cells, resulting in diffuse and strong S-100 and SOX10 positivity. Neurofibromas contain a mix of cell types, leading to patchy S-100 staining and CD34 positivity in the stromal network.

Question 3727

Topic: Soft Tissue Tumors & Metastasis

A 35-year-old patient presents with multiple painful peripheral schwannomas but lacks bilateral vestibular schwannomas. Genetic testing reveals a mutation in the SMARCB1 (INI1) gene. What is the most likely diagnosis?

. Schwannomatosis
. Neurofibromatosis type 1
. Neurofibromatosis type 2
. Multiple Endocrine Neoplasia type 2B
. Li-Fraumeni syndrome

Correct Answer & Explanation

. Schwannomatosis

Explanation

Schwannomatosis is a distinct genetic condition characterized by multiple schwannomas without the vestibular involvement seen in NF2. It is typically associated with mutations in the SMARCB1 (INI1) or LZTR1 genes.

Question 3728

Topic: Soft Tissue Tumors & Metastasis

During the histopathological review of an excised peripheral soft tissue mass, the pathologist identifies Verocay bodies. What do these specific structures consist of?

. Parallel rows of palisading Schwann cell nuclei separated by anucleate eosinophilic processes
. Wavy collagen bundles interspersed with mast cells
. Clusters of foamy histiocytes surrounding areas of necrosis
. Multinucleated giant cells engulfing hemosiderin
. Rosettes of primitive neuroectodermal cells around a central neuropil core

Correct Answer & Explanation

. Parallel rows of palisading Schwann cell nuclei separated by anucleate eosinophilic processes

Explanation

Verocay bodies are characteristic histologic features found in the Antoni A areas of schwannomas. They consist of stacked, parallel rows of palisading nuclei separated by pink, anucleate zones of cytoplasmic processes.

Question 3729

Topic: 10. Pathology and Oncology

What is the approximate lifetime risk of a plexiform neurofibroma undergoing malignant transformation to an MPNST in a patient with Neurofibromatosis type 1?

. Less than 1%
. 2 to 3%
. 8 to 13%
. 25 to 30%
. Greater than 50%

Correct Answer & Explanation

. 8 to 13%

Explanation

Patients with NF1 have an estimated 8% to 13% lifetime risk of developing a Malignant Peripheral Nerve Sheath Tumor (MPNST). These nearly always arise from pre-existing plexiform neurofibromas.

Question 3730

Topic: 10. Pathology and Oncology

A 40-year-old male presents with a painless, slow-growing mass in the posterior thigh. MRI reveals a "split-fat" sign and a "fascicular" sign within the lesion. Which of the following is true regarding its management?

. It requires wide local excision with 2 cm margins
. Excision can typically be performed while preserving the parent nerve via enucleation
. It is highly malignant and requires neoadjuvant chemotherapy
. Amputation is the definitive treatment of choice
. It must be treated with primary radiation therapy prior to resection

Correct Answer & Explanation

. Excision can typically be performed while preserving the parent nerve via enucleation

Explanation

The "split-fat" and "fascicular" signs on MRI are characteristic of benign peripheral nerve sheath tumors, most commonly schwannomas. They can typically be treated with marginal enucleation, preserving the continuity of the parent nerve.

Question 3731

Topic: Soft Tissue Tumors & Metastasis

Which of the following clinical or anatomical characteristics accurately differentiates a solitary neurofibroma from a schwannoma?

. Neurofibromas incorporate nerve fascicles throughout the tumor substance
. Schwannomas lack a true epineurial capsule
. Neurofibromas uniquely possess Verocay bodies
. Schwannomas are always centrally located within the nerve
. Neurofibromas exclusively affect cranial nerves

Correct Answer & Explanation

. Neurofibromas incorporate nerve fascicles throughout the tumor substance

Explanation

Neurofibromas grow intrinsically within the nerve, intertwining with and separating the nerve fascicles, making nerve-sparing resection difficult. Schwannomas grow eccentrically and push the fascicles aside beneath a true capsule.

Question 3732

Topic: Soft Tissue Tumors & Metastasis

A 35-year-old female presents with a growing mass in her popliteal fossa. Histology demonstrates a variable mix of Schwann cells, fibroblasts, and perineurial cells, with mast cells scattered among spindle cells with wavy nuclei. What is the most likely diagnosis?

. Neurofibroma
. Schwannoma
. MPNST
. Synovial sarcoma
. Fibroma of tendon sheath

Correct Answer & Explanation

. Neurofibroma

Explanation

The presence of a heterogeneous cell population (Schwann cells, fibroblasts, mast cells) with wavy, "buckled" nuclei is the classic histologic description of a neurofibroma. Schwannomas are more homogenous.

Question 3733

Topic: Bone Tumors

In a patient with Neurofibromatosis Type 1, which skeletal manifestation is considered a characteristic diagnostic criterion?

. Anterolateral tibial bowing
. Posteromedial tibial bowing
. Polyostotic fibrous dysplasia
. Multiple osteochondromas
. Spondyloepiphyseal dysplasia

Correct Answer & Explanation

. Anterolateral tibial bowing

Explanation

Anterolateral tibial bowing (often progressing to congenital pseudarthrosis of the tibia) is a classic skeletal manifestation and a diagnostic criterion for NF1. Posteromedial bowing is typically associated with calcaneovalgus foot deformity and resolves spontaneously.

Question 3734

Topic: 10. Pathology and Oncology

A biopsy of a rapidly expanding peripheral nerve tumor in a patient with NF1 shows complete loss of H3K27me3 expression on immunohistochemistry. This finding is highly specific for which of the following?

. Malignant peripheral nerve sheath tumor (MPNST)
. Atypical neurofibroma
. Cellular schwannoma
. Clear cell sarcoma
. Epithelioid sarcoma

Correct Answer & Explanation

. Malignant peripheral nerve sheath tumor (MPNST)

Explanation

Loss of trimethylation at lysine 27 of histone H3 (H3K27me3) is a highly specific and sensitive immunohistochemical marker for MPNST. It helps differentiate MPNST from benign nerve sheath tumors and other high-grade sarcomas.

Question 3735

Topic: 10. Pathology and Oncology

When attempting to surgically resect a major nerve plexiform neurofibroma that is causing severe intractable pain and progressive motor deficit, the surgeon should counsel the patient on which expected outcome?

. High likelihood of permanent neurologic deficit requiring possible nerve grafting
. Nerve preservation is almost always possible with microsurgical techniques
. The tumor will naturally separate from the fascicles along a defined plane
. Radiotherapy will shrink the tumor, eliminating the need for surgical resection
. Preoperative embolization is curative and avoids surgical morbidity

Correct Answer & Explanation

. High likelihood of permanent neurologic deficit requiring possible nerve grafting

Explanation

Plexiform neurofibromas grow infiltratively among the fascicles of multiple nerve branches. Resection inevitably requires sacrificing functional nerve tissue, carrying a high risk of permanent neurologic deficit.

Question 3736

Topic: 10. Pathology and Oncology

Which of the following is the most appropriate initial management for an asymptomatic, small (1.5 cm), solitary neurofibroma of the ulnar nerve found incidentally on MRI?

. Clinical observation and serial imaging
. Marginal surgical excision
. Wide local resection with primary nerve repair
. Adjuvant external beam radiation
. Systemic MEK inhibitors

Correct Answer & Explanation

. Clinical observation and serial imaging

Explanation

Incidental, asymptomatic, small benign peripheral nerve sheath tumors (like solitary neurofibromas) should be managed with observation. Surgical intervention risks iatrogenic nerve injury and should be reserved for symptomatic or growing lesions.

Question 3737

Topic: Soft Tissue Tumors & Metastasis

The "target sign" seen on T2-weighted MRI of a schwannoma corresponds histologically to which of the following spatial arrangements?

. Central dense Antoni A tissue and peripheral myxoid Antoni B tissue
. Central necrosis and peripheral hypercellularity
. Central hemorrhage and peripheral edema
. Central calcification and peripheral fat deposition
. Central Antoni B tissue and peripheral Antoni A tissue

Correct Answer & Explanation

. Central dense Antoni A tissue and peripheral myxoid Antoni B tissue

Explanation

The T2 target sign represents a central area of low signal intensity (highly cellular Antoni A tissue with dense collagen) surrounded by a peripheral rim of high signal intensity (myxoid, hypocellular Antoni B tissue).

Question 3738

Topic: 10. Pathology and Oncology

A 50-year-old male undergoes marginal enucleation of a solitary schwannoma of the sciatic nerve. Postoperatively, he experiences neuropraxia in the distribution of the peroneal division. What is the most likely cause of this complication?

. Traction injury to the adjacent nerve fascicles during enucleation
. Inadvertent en bloc excision of the entire nerve segment
. Direct transection of the main nerve trunk
. Thermal necrosis from bipolar electrocautery at the skin level
. Vascular compromise of the vasa nervorum extending proximally

Correct Answer & Explanation

. Traction injury to the adjacent nerve fascicles during enucleation

Explanation

Neuropraxia following enucleation of a schwannoma is common and typically results from surgical traction on the true nerve fascicles stretched over the tumor capsule. Function usually recovers over weeks to months.

Question 3739

Topic: Soft Tissue Tumors & Metastasis
Which of the following diagnostic criteria is sufficient to establish a definitive clinical diagnosis of Neurofibromatosis Type 2 (NF2)?
. Bilateral vestibular schwannomas on MRI
. Presence of an optic pathway glioma
. Six or more café-au-lait macules
. Axillary or inguinal freckling
. Congenital pseudarthrosis of the tibia

Correct Answer & Explanation

. Bilateral vestibular schwannomas on MRI

Explanation

Bilateral vestibular schwannomas are the hallmark of NF2 and are sufficient alone to make the diagnosis. The other options listed (optic glioma, café-au-lait spots, freckling, tibial pseudarthrosis) are diagnostic criteria for NF1.

Question 3740

Topic: 10. Pathology and Oncology

A 45-year-old female presents with a slow-growing, painful mass in her volar forearm. MRI shows a well-circumscribed lesion eccentrically located on the median nerve. During exploration, the mass is easily shelled out without damaging the nerve fascicles. Which of the following histologic features is most likely present?

. Plexiform arrangement of nerve fascicles
. Spindle cells interwoven with "shredded carrot" collagen
. Alternating Antoni A and Antoni B areas
. S-100 negative tumor cells in a myxoid stroma
. Infiltration of the nerve epineurium

Correct Answer & Explanation

. Alternating Antoni A and Antoni B areas

Explanation

The clinical and surgical presentation describes a schwannoma, which is encapsulated and eccentric, allowing for enucleation. Histologically, schwannomas are characterized by alternating cellular (Antoni A with Verocay bodies) and hypocellular (Antoni B) areas.

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