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Background: Atypical lentiginous melanocytic nevi (ALMNs) are atypical pigmented lesions with histopathological features similar to those of dysplastic nevi, with a lentiginous pattern. Variable histopathological features of ALMNs were observed in our practice., Methods: We described the histopathological features of ALMNs diagnosed in the period 2009-2015. Our cases were divided into 2 groups: Group 1: ALMNs showing the same histopathological features as previously described in the literature; Group 2: ALMNs with different features., Results: Twenty-nine ALMNs were diagnosed; 2 groups of ALMNs were identified. Group 1 ALMNs showed a constant, mild epidermal acanthosis; frequently, an inflammatory infiltrate and dermal fibrosis, cytological atypia and mild architectural atypia. Group 2 ALMNs showed a constant psoriasis-like acanthosis with a hypercellularity of the rete ridges; cytological atypia was rare, whereas architectural atypia was constantly observed. Immunohistochemistry (MART-1 staining) revealed that the melanocytes were localized at the dermo-epidermal junction in both groups. ALMNs showed a broad spectrum of histopathological features., Conclusions: Our main finding was a constant architectural atypia in all lesions of Group 2. The identification of a unique type of ALMN seems no longer possible. The correct recognition of such benign, though atypical, melanocytic lesions is important in order to avoid an overdiagnosis of cutaneous melanoma and to prevent their potential evolution to the latter.

Thirteen melanocytic skin neoplasms with a consultation diagnosis by A. Bernard Ackerman were submitted to immunohistochemistry for HMB-45, Ki67, cyclin D1, e-cadherin, and p16; 9/13 cases underwent fluorescence in situ hybridization (FISH) test targeting 6p25 (RREB1), 6q23 (MYB), centromere 6 (Cep6), and 11q13 (CCND1), as well as the centromere 7 (Cep7). A "consensus diagnosis" among 3 experts was also advocated both before and after morphomolecular information. Three neoplasms with a consultation diagnosis of Spitz nevus showed at least 3 abnormal immunohistochemical patterns; 2 of these cases were also FISH-positive for CCND1 gain, but none of them had a final consensus diagnosis of melanoma. Two neoplasms with a consultation diagnosis of congenital nevus received a consensus diagnosis of melanoma. Molecular morphology techniques can highlight the atypical features of melanocytic neoplasms and support existence of a morphobiologic "spectrum": This should be mirrored in the final report by abandoning the dichotomic (benign vs malignant) diagnostic approach.