Biography
Biography: Emily N C Ryder
Abstract
Perineuriomatous melanocytic naevi are acquired melanocytic naevi with dual melanocytic and perineural differentiation. These tumours may resemble neurofibromas, sclerozing naevi or even desmoplastic melanomas but are distinguished by their lack of cytological atypia and positive staining for EMA and Melan A. Melanocyte and peripheral nerve sheath tumors respectively are usually regarded as distinct tumor types, although both cell lineages originate from the pleuripotent embryological neural crest and both commonly express SOX10 and S100. We had reviewed the literature and present a possibly unique case with multiple such perineuriomatous melanocytic naevi. A 64-year-old Caucasian man presented with dozens of asymptomatic soft papules scattered on his proximal thighs and trunk with subtle foci of pigmentation. Histopathologically each excised lesion was a well-circumscribed compound melanocytic tumour with superficial aspects resembling a common naevus. Melanocytes in the reticular dermis merged with populations of spindled cells in parallel bundles and whorls, within a collagenous stroma with pericellular cracking/clefting. There was no cytological atypia or mitotic activity. Immunohistochemistry demonstrated Melan-A positive superficial melanocytes, whilst the spindle cells were positive for EMA but lacked SOX-10 or Melan-A. Interphase FISH using the Human Centromeric Probe for chromosomes 13/21, subtelomeric probes for 13q, 21q, and 22q, did not identify an abnormality on examination of 100 cells. This possibly unique presentation provides support for the hypothesis that a germline mutation may be responsible for the pathogenesis of these lesions. We suggest this has implications for pathogenesis of this tumorhybrid phenomenon. Further genetic studies may help shed light further on this phenomenon.