Schwannomas are benign peripheral nerve sheath tumors believed to be composed purely of cells with ultrastructural features of Schwann cells.
Schwannomas are believed to develop eccentrically from the surface of nerves and not to contain axons, other than immediately beneath the capsule. This concept has recently been disputed in cases associated with neurofibromatosis type 2 (NF2).
The usual presence of intratumoral axons in neurofibromas is said to allow easy distinction from schwannomas. The frequent presence of intratumoral axons in schwannomas argues against conventional views of these lesions’ pathogenesis as an eccentric encapsulated lesion and raises the possibility that a more diverse cell population, perhaps more closely resembling neurofibromas, may constitute these neoplasms. (17721192)
Although NFP-positive axons were most often present in the conventional and cellular variants of schwannoma, their presence was also observed in a minority of ancient, gastric and plexiform schwannomas. (17721192)
Differentiation between neurofibroma and schwannoma in cases with overlapping cytoarchitectural features should not be based solely on the presence or absence of NFP-positive axons within a given tumor. (17721192)
Variants
deep-seated plexiform schwannoma
cellular schwannoma
melanotic schwannoma
plexiform schwannoma
Immunochemistry
S-100 +
neurofilament + (NF)
- NF-positive axons in conventional schwannomas (55%) and cellular schwannomas (75%) (17721192)
Gene mutations
somatic mutations or deletions of NF2
See also