Cutaneous microcystic/reticular schwannoma: a poorly recognized entity.
BACKGROUND
Microcystic/ reticular schwannoma is exceptionally rare yet distinctive morphological variant of schwannoma with predilection for visceral sites lacking association with neurofibromatosis.


OBJECTIVE
To further delineate clinicopathological features of cutaneous microcystic/reticular schwannoma and to discuss its differential diagnosis.


RESULTS
We analyzed three cutaneous microcystic/reticular schwannomas, occurring in two males and one female (mean age: 37.6 years). The tumors presented as a non-painful slightly raised papule (mean: 0.7 cm) on upper arm (n = 2) and back (n = 1). No recurrences were observed despite marginal excision (mean follow up: 42 months). Histopathologically, a multilobular proliferation was present in the dermis composed of bland tumor cells forming distinctive microcystic, reticular, lace-like or pseudoglandular structures, containing abundant myxoid/mucinous material. By immunohistochemistry, tumor cells lining microcystic structures corresponded to Schwann cells (diffuse S100 positive, variable GFAP positivity). A discontinuous EMA-positive perineurium was present at the periphery of some of the lobules.


CONCLUSIONS
Cutaneous microcystic/reticular schwannoma expands the spectrum of benign peripheral nerve sheath tumors with reticular morphology encountered in the skin. Other tumors in this group include reticular perineurioma and hybrid tumors with reticular morphology, e.g. reticular perineurioma/schwannoma and reticular perineurioma/neurofibroma.
Institute of Pathology, Medical Faculty University of Ljubljana, Ljubljana, Slovenia.
Boštjan
B
Luzar
Department of Dermatology, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima, Japan.
Maiko
M
Tanaka
Division of Anatomical Pathology at University of Stellenbosch, Cape Town, South Africa.
Johann
J
Schneider
Department of Dermatopathology, St John's Institute of Dermatology, St Thomas' Hospital, London, UK.
Eduardo
E
Calonje
D000328:Adult; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009442:Neurilemmoma / Q000378:metabolism / Q000473:pathology*; D012878:Skin Neoplasms / Q000378:metabolism / Q000473:pathology*
benign peripheral nerve sheath tumors; microcystic/reticular schwannoma; reticular hybrid tumors; reticular morphology; reticular perineurioma; skin