Simulants of malignant melanoma

During the recent period, dermoscopy has yielded improvement in
the early disclosure of various atypical melanocytic neoplasms (AMN)
of the skin. Beyond this clinical procedure, AMN histopathology
remains mandatory for establishing their precise diagnosis. Of note,
panels of experts in AMN merely report moderate agreement in various
puzzling cases. Divergences in opinion and misdiagnosis are likely
increased when histopathological criteria are not fine-tuned and
when facing a diversity of AMN types. Furthermore, some AMN have
been differently named in the literature including atypical Spitz tumor,
metastasizing Spitz tumor, borderline and intermediate melanocytic
tumor, malignant Spitz nevus, pigmented epithelioid melanocytoma or
animal-type melanoma. Some acronyms have been further suggested
such as MELTUMP (after melanocytic tumor of uncertain malignant
potential) and STUMP (after Spitzoid melanocytic tumor of uncertain
malignant potential). In this review, such AMN at the exclusion of
cutaneous malignant melanoma (MM) variants, are grouped under the
tentative broad heading skin melanocytoma. Such set of AMN frequently
follows an indolent course, although they exhibit atypical and
sometimes worrisome patterns or cytological atypia. Rare cases of skin
melanocytomas progress to loco regional clusters of lesions (agminate
melanocytomas), and even to regional lymph nodes. At times, the distinction
between a skin melanocytoma and MM remains puzzling.
However, multipronged immunohistochemistry and emerging molecular
biology help profiling any malignancy risk if present.