Genetic Studies on a Case of Eruptive Disseminated Spitz Nevus and Review of Other 33 Cases.

Eruptive disseminated Spitz nevus is an uncommon presentation of Spitz nevi. Only a few tens of cases have been published and only 6 of them have genetic studies. We present an additional case of a 29-year-old woman with dozens of Spitz nevi which had appeared since she was aged 10 years. The nevi were located on arms, inner thighs, legs, and buttocks. Nine of them were biopsied. Four presented severe atypia. Immunohistochemistry was performed on 5 of the biopsied specimens and was negative for PRAME, ROS-1, PDL-1, pan-TRK, and ALK. Molecular studies on the largest lesion demonstrated no NTRK1, NTRK2, or NTRK3 fusions. FISH study for PTEN showed no alteration in that same lesion. Next-generation sequencing was also negative for any detectable mutations in numerous genes analyzed. In conclusion, it seems reasonable to be cautious when evaluating atypia, even if severe, in cases of eruptive disseminated Spitz nevus.