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10. Pathology and Oncology MCQs

Practice Set 186 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 3701

Topic: 10. Pathology and Oncology

During surgical exploration for a mass in the popliteal fossa causing mild paresthesias, the surgeon encounters an encapsulated mass eccentrically located on the tibial nerve. The nerve fascicles are splayed over the capsule. What is the most appropriate surgical management?

. En bloc resection with 2 cm margins
. Marginal enucleation while preserving nerve continuity
. Incisional biopsy and closure
. Segmental nerve resection with immediate cable grafting
. Amputation proximal to the mass

Correct Answer & Explanation

. Marginal enucleation while preserving nerve continuity

Explanation

Schwannomas grow eccentrically and are surrounded by a true capsule (epineurium), displacing the nerve fascicles. They can typically be safely shelled out (marginal enucleation) while preserving the continuity and function of the nerve.

Question 3702

Topic: Soft Tissue Tumors & Metastasis

Which of the following macroscopic and microscopic growth patterns best differentiates a solitary neurofibroma from a schwannoma?

. Central growth with intimate incorporation of nerve fascicles
. Eccentric growth with a true definable capsule
. Exclusive growth within the epineurium without axonal involvement
. Avascular core with peripheral vascularity
. Peripheral palisading of cells mimicking a granuloma

Correct Answer & Explanation

. Central growth with intimate incorporation of nerve fascicles

Explanation

Neurofibromas grow centrally and intimately involve the nerve fascicles, lacking a true capsule. Unlike schwannomas, they cannot be easily enucleated without sacrificing the involved nerve.

Question 3703

Topic: 10. Pathology and Oncology

A 22-year-old female with known Neurofibromatosis type 1 (NF1) presents with rapid enlargement of a long-standing "bag of worms" mass in her thigh. Which specific type of benign nerve sheath tumor carries the highest risk of malignant transformation in this patient?

. Solitary encapsulated schwannoma
. Cutaneous neurofibroma
. Plexiform neurofibroma
. Vestibular schwannoma
. Traumatic neuroma

Correct Answer & Explanation

. Plexiform neurofibroma

Explanation

Plexiform neurofibromas are pathognomonic for NF1 and have a 5-10% lifetime risk of transforming into a Malignant Peripheral Nerve Sheath Tumor (MPNST). Cutaneous neurofibromas do not carry this malignant potential.

Question 3704

Topic: 10. Pathology and Oncology

Neurofibromatosis type 1 (von Recklinghausen disease) is an autosomal dominant disorder associated with multiple neurofibromas. Which of the following details the correct genetic mutation and corresponding gene product?

. Chromosome 22, merlin
. Chromosome 11, EWS-FLI1
. Chromosome 17, p53
. Chromosome 17, neurofibromin
. Chromosome 22, neurofibromin

Correct Answer & Explanation

. Chromosome 17, neurofibromin

Explanation

NF1 is caused by a mutation on chromosome 17, which encodes the tumor suppressor protein neurofibromin. NF2 is associated with chromosome 22 and the protein merlin (schwannomin).

Question 3705

Topic: Soft Tissue Tumors & Metastasis

A 30-year-old male is diagnosed with Neurofibromatosis type 2 (NF2). He is at highest risk for developing which of the following pathognomonic lesions?

. Bilateral vestibular schwannomas
. Unilateral plexiform neurofibroma
. Multiple cutaneous neurofibromas
. Tibial pseudarthrosis
. Optic nerve glioma

Correct Answer & Explanation

. Bilateral vestibular schwannomas

Explanation

The hallmark of NF2 is the development of bilateral vestibular schwannomas (acoustic neuromas). NF1 is associated with plexiform neurofibromas, optic gliomas, and tibial pseudarthrosis.

Question 3706

Topic: 10. Pathology and Oncology

On physical examination of a patient with a suspected benign peripheral nerve sheath tumor in the upper extremity, which of the following findings is most characteristic?

. Mobility in all directions equally
. Mobility in the transverse plane but tethered in the longitudinal plane
. Complete fixation to underlying bone
. Overlying pulsatile thrill and bruit
. Severe pain upon light brushing of the skin (allodynia)

Correct Answer & Explanation

. Mobility in the transverse plane but tethered in the longitudinal plane

Explanation

Benign nerve sheath tumors (like schwannomas and neurofibromas) are typically mobile transversely across the nerve but are restricted longitudinally because they are tethered to the nerve itself.

Question 3707

Topic: 10. Pathology and Oncology

Immunohistochemical staining is performed on a biopsy of a suspected peripheral nerve sheath tumor. Which staining pattern most strongly supports a diagnosis of schwannoma over neurofibroma?

. Strong positive staining for SMA and Desmin
. Negative S-100 with positive EMA
. Strong, uniform, diffuse positivity for S-100
. Patchy, weak positivity for S-100
. Positive staining for CD34 and STAT6

Correct Answer & Explanation

. Strong, uniform, diffuse positivity for S-100

Explanation

Schwannomas are composed almost entirely of neoplastic Schwann cells and show strong, diffuse positivity for S-100. Neurofibromas have a mixed cell population and typically show only patchy or weak S-100 staining.

Question 3708

Topic: 10. Pathology and Oncology

Histological evaluation of a nerve sheath tumor reveals alternating Antoni A and Antoni B areas. Which of the following best describes the microscopic appearance of the Antoni B areas?

. Dense, hypercellular spindle cells with palisading
. Nests of cells separated by prominent fibrous bands
. Whorls of meningothelial cells with psammoma bodies
. Hypocellular, loosely arranged cells in a myxoid stroma
. Sheets of uniform small round blue cells

Correct Answer & Explanation

. Hypocellular, loosely arranged cells in a myxoid stroma

Explanation

Antoni B areas in a schwannoma are hypocellular, loosely textured, and rich in a myxoid, edematous stroma. Antoni A areas are hypercellular with compact spindle cells.

Question 3709

Topic: Soft Tissue Tumors & Metastasis

Which of the following microscopic features is a classic hallmark of a neurofibroma?

. Wavy spindle cells with interspersed mast cells and collagen bundles
. Biphasic synovial-like cells with glandular formations
. Verocay bodies and thick-walled hyalinized blood vessels
. Intracytoplasmic mucin droplets and signet ring cells
. Atypical lipoblasts with hyperchromatic scalloped nuclei

Correct Answer & Explanation

. Wavy spindle cells with interspersed mast cells and collagen bundles

Explanation

Neurofibromas are characterized microscopically by wavy spindle cells (buckled nuclei) in a variably myxoid/collagenous background, frequently accompanied by numerous mast cells.

Question 3710

Topic: 10. Pathology and Oncology
A patient with NF1 has a known plexiform neurofibroma. Which of the following clinical changes is the most ominous sign suggesting malignant transformation to an MPNST?
. Gradual increase in size over 10 years
. Development of an overlying café-au-lait spot
. A positive Tinel's sign at the proximal margin
. Transverse mobility of the mass on exam
. Sudden onset of intractable pain at rest and rapid enlargement

Correct Answer & Explanation

. Sudden onset of intractable pain at rest and rapid enlargement

Explanation

Malignant transformation of a plexiform neurofibroma to a Malignant Peripheral Nerve Sheath Tumor (MPNST) is clinically signaled by rapid growth, new-onset firm consistency, and intractable pain at rest.

Question 3711

Topic: 10. Pathology and Oncology

Magnetic Resonance Imaging (MRI) of a benign nerve sheath tumor often reveals the "target sign." What MRI characteristics define this sign?

. Peripheral hyperintensity and central hypointensity on T1-weighted images
. Peripheral hyperintensity and central hypointensity on T2-weighted images
. Central hyperintensity and peripheral hypointensity on T2-weighted images
. Diffuse uniform enhancement with central necrosis on post-contrast imaging
. A fatty halo surrounding a dark fibrous core on T1-weighted images

Correct Answer & Explanation

. Peripheral hyperintensity and central hypointensity on T2-weighted images

Explanation

The "target sign" on T2-weighted MRI consists of peripheral hyperintensity (representing myxoid Antoni B tissue) and central hypointensity (representing fibrocollagenous Antoni A tissue). It strongly suggests a benign nerve sheath tumor.

Question 3712

Topic: Soft Tissue Tumors & Metastasis

A 14-year-old boy presents with a massive, diffuse, tortuous swelling of his right upper extremity. Palpation of the mass yields a sensation described as a "bag of worms." This lesion is considered pathognomonic for which condition?

. Schwannomatosis
. Neurofibromatosis type 2
. Neurofibromatosis type 1
. Multiple Endocrine Neoplasia type 2B
. Sturge-Weber syndrome

Correct Answer & Explanation

. Neurofibromatosis type 1

Explanation

The "bag of worms" palpation refers to a plexiform neurofibroma. This lesion involves multiple nerve fascicles and branches, and is strictly pathognomonic for Neurofibromatosis type 1 (NF1).

Question 3713

Topic: 10. Pathology and Oncology

A 50-year-old male is diagnosed with a high-grade Malignant Peripheral Nerve Sheath Tumor (MPNST) of the sciatic nerve. Staging shows no metastasis. What is the mainstay of definitive surgical treatment?

. Marginal enucleation sparing the sciatic fascicles
. Intralesional curettage with phenol adjuvant
. Chemotherapy alone as these tumors are highly chemosensitive
. Wide surgical resection, often necessitating nerve sacrifice
. Epineurial stripping and observation

Correct Answer & Explanation

. Wide surgical resection, often necessitating nerve sacrifice

Explanation

MPNST is a highly aggressive sarcoma. The standard of care is wide surgical resection with negative margins, which almost always necessitates sacrificing the involved nerve. Neoadjuvant or adjuvant radiation is often utilized.

Question 3714

Topic: Soft Tissue Tumors & Metastasis

A patient presents with multiple distinct schwannomas in the extremities but lacks vestibular schwannomas. Genetic testing reveals a mutation distinct from NF1 and NF2. Which gene is most commonly implicated in this condition (Schwannomatosis)?

. SMARCB1 (INI1) or LZTR1
. APC
. TP53
. Rb1
. PTEN

Correct Answer & Explanation

. SMARCB1 (INI1) or LZTR1

Explanation

Schwannomatosis is a distinct clinical entity from NF1 and NF2, characterized by multiple schwannomas without bilateral acoustic neuromas. It is most commonly associated with mutations in the SMARCB1 (INI1) or LZTR1 genes.

Question 3715

Topic: 10. Pathology and Oncology

A 40-year-old patient presents with a biopsy-confirmed solitary schwannoma of the median nerve. The patient is anxious about the mass becoming malignant. What is the approximate risk of malignant transformation for a solitary schwannoma?

. 5-10%
. 15-20%
. 25-30%
. 50%
. Essentially zero

Correct Answer & Explanation

. Essentially zero

Explanation

Unlike neurofibromas (specifically the plexiform type in NF1), solitary schwannomas have virtually no risk of malignant transformation. They are completely benign lesions.

Question 3716

Topic: 10. Pathology and Oncology

A 3-year-old child presents with anterolateral bowing of the tibia. Radiographs show medullary sclerosis and cortical thinning. If this child has an underlying genetic syndrome, which of the following is the most likely associated nerve sheath tumor pathology?

. Bilateral vestibular schwannomas
. Plexiform neurofibroma
. Solitary encapsulated schwannoma
. Meningioma
. Ependymoma

Correct Answer & Explanation

. Plexiform neurofibroma

Explanation

Anterolateral tibial bowing (and subsequent pseudarthrosis) is a classic orthopedic manifestation of NF1. The characteristic nerve sheath tumor associated with NF1 is the neurofibroma, notably the plexiform neurofibroma.

Question 3717

Topic: 10. Pathology and Oncology

During histologic review of an aggressive spindle cell sarcoma arising from a major nerve, the pathologist suspects an MPNST. Compared to a benign schwannoma, what change in S-100 immunohistochemical staining is expected in an MPNST?

. Increased diffuse staining
. No change; both remain strongly and diffusely positive
. Patchy, weak, or complete loss of S-100 expression
. Shift from nuclear to exclusive cytoplasmic staining
. S-100 is replaced by strong Desmin positivity

Correct Answer & Explanation

. Patchy, weak, or complete loss of S-100 expression

Explanation

As malignant peripheral nerve sheath tumors (MPNST) de-differentiate, they typically lose the strong, diffuse S-100 positivity seen in benign nerve sheath tumors, resulting in patchy, weak, or negative S-100 staining.

Question 3718

Topic: Soft Tissue Tumors & Metastasis
A 12-year-old boy is suspected of having Neurofibromatosis type 1. Which of the following is an established clinical diagnostic criterion for NF1 according to the NIH guidelines?
. Presence of 2 or more café-au-lait macules greater than 5 mm
. Presence of 4 or more café-au-lait macules greater than 15 mm
. A solitary neurofibroma of any size
. Presence of 6 or more café-au-lait macules (size >5 mm prepubertal or >15 mm postpubertal)
. Bilateral acoustic neuromas on MRI

Correct Answer & Explanation

. Presence of 6 or more café-au-lait macules (size >5 mm prepubertal or >15 mm postpubertal)

Explanation

The NIH diagnostic criteria for NF1 require at least two features, one of which can be the presence of 6 or more café-au-lait spots (measuring >5 mm in prepubertal individuals and >15 mm in postpubertal individuals).

Question 3719

Topic: Soft Tissue Tumors & Metastasis

Which of the following describes the cellular composition of a neurofibroma compared to a schwannoma?

. Neurofibromas contain a heterogeneous mix of Schwann cells, perineurial cells, fibroblasts, and mast cells.
. Neurofibromas are composed purely of monoclonal neoplastic Schwann cells.
. Neurofibromas lack fibroblasts and are composed exclusively of mast cells.
. Schwannomas contain a dense population of axons within their central core.
. Schwannomas lack S-100 expressing cells entirely.

Correct Answer & Explanation

. Neurofibromas contain a heterogeneous mix of Schwann cells, perineurial cells, fibroblasts, and mast cells.

Explanation

Neurofibromas are heterogeneous, unencapsulated tumors containing Schwann cells, fibroblasts, perineurial-like cells, and mast cells admixed with axons. In contrast, schwannomas are predominantly homogeneous proliferations of neoplastic Schwann cells.

Question 3720

Topic: 10. Pathology and Oncology

A 45-year-old female presents with a slow-growing volar forearm mass. The mass is mobile transversely but not longitudinally. Histologic examination reveals a biphasic architecture with hypercellular areas of nuclear palisading and hypocellular myxoid areas. What is the most likely diagnosis?

. Neurofibroma
. Schwannoma
. Malignant peripheral nerve sheath tumor (MPNST)
. Traumatic neuroma
. Desmoid fibromatosis

Correct Answer & Explanation

. Schwannoma

Explanation

The clinical presentation and histology (Antoni A hypercellular areas with nuclear palisading and Antoni B hypocellular areas) are pathognomonic for a schwannoma. Schwannomas are encapsulated and typically displace nerve fascicles eccentrically.

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