Fig. 3: Specific CGH/SNP-array abnormalities in benign or indolent melanocytic tumors.

a–c Desmoplastic Spitz nevus. a Intradermal melanocytic proliferation with pronounced desmoplastic stromal reaction and infiltrative growth pattern. b Epithelioid cells with a large nuclei, prominent nucleoli, and abundant amphophilic cytoplasm. Two mitotic figures are noted in the center of the field (arrows). c SNP array showing a gain of 11p (arrow) with no additional abnormalities, suggesting a desmoplastic Spitz nevus. d–f BAP1-inactivated tumor. d Large, predominantly intradermal tumor with biphenotypic morphology and a lymphocytic host response. e Top, majority of the lesion is composed of epithelioid cells with large nuclei, prominent nucleoli, and abundant eosinophilic cytoplasm with distinct cell membrane. Bottom, a component or ordinary nevus is identified. f SNP array showing a loss of 3p21 (arrow) with no additional abnormalities, suggesting an indolent BAP1-inactivated tumor/nevus. g–i Proliferative nodule arising in congenital nevus. g Hypercellular non-expansile dermal nodule composed of densely packed uniform melanocytes. h Melanocytes with round to oval hyperchromatic and slightly irregularly shaped nuclei with a moderate amount of eosinophilic cytoplasm, high nuclear to cytoplasmic ratio, and increased mitotic rate. i SNP array showing gains of whole chromosomes 2, 6, 13, 15, 16, and 22 suggestive of a proliferative nodule (arrow). j–l Low-risk atypical Spitz tumor with NTRK1 rearrangements. j Predominately intradermal melanocytic proliferation with a bulbous profile. k Epithelioid cells with intermediate size nuclei and moderate amount of eosinophilic cytoplasm arranged in back to back small nests with occasional mitotic figures (arrow). l SNP array results showing chromosome 1q. A small deletion is noted with breakpoints within LMNA and NTRK1 genes (arrows) resulting in an LMNA-NTRK1 fusion product.