Melanocytic naevi with perineurial differentiation a distinctive variant of neurotised naevi and a diagnostic pitfall with desmoplastic melanoma

Ingrid Ferreira, Peter Kind, Ivo Van Den Berghe, Lucy Melly, Felix Offner, Jason L Hornick, Thomas Brenn

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AIMS: Spindle cell differentiation is not an uncommon finding in common acquired naevi and may represent a form of neurotisation with Schwannian differentiation of melanocytes. Perineurial differentiation in this context appears to be distinctly rare and is only poorly documented in the literature.

METHODS AND RESULTS: We have identified six melanocytic tumours showing spindle cell morphology and perineurial differentiation from routine and referral material. Clinical data and follow-up were obtained, and the histological and immunohistochemical features were analysed. The tumours affected middle aged adults (median: 48; range: 26-74 years) with a wide anatomical distribution and benign follow up (median: 13; range: 6 to 48 months). All tumours were nodular and circumscribed but asymmetrical with extension into deep dermis and superficial subcutis. A characteristic finding was a biphasic growth pattern with a lentiginous compound naevus in the superficial aspect and abrupt transition to a prominent nodular spindle cell proliferation in the deeper reaches. Spindle cells were bland and uniform and arranged singly and in short fascicles in a loose fibromyxoid stroma. In areas, a whorled arrangement of slender spindle cells with wavy nuclei was appreciated. Distinctive intratumoral hypocellular nodules and peripheral lymphoid aggregates were additional features. By immunohistochemistry, the spindle cells were mainly S100-positive melanocytes. In areas, S100-/EMA+ spindle cells showing co-expression of glut-1 and claudin-1 were closely admixed.

CONCLUSION: This perineurial differentiation likely represents a rare and unusual form of neurotisation. The tumours are benign but may be mistaken for desmoplastic melanoma. Awareness and careful attention to the clinico-pathological and immunohistochemical features allows reliable separation. This article is protected by copyright. All rights reserved.

Original languageEnglish
Early online date14 Dec 2017
Publication statusE-pub ahead of print - 14 Dec 2017


  • Journal Article


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