Animal-type melanoma: report of five cases with sentinel node biopsy and fluorescence in-situ hybridization analysis

"Animal-Type Melanoma/Pigmented Epithelioid Melanocytoma": History and Features of a Controversial Entity

Animal-type melanoma (ATM) was first described in the literature by Levene in 1979 in relation to a patient with a characteristic clinical presentation, and only later, rare and anecdotal case series have tried to shed light on an entity that has undergone several nosographic classification changes, and which, since 2018, is classified under the term "pigmented epithelioid melanocytoma". Here, we conduct a brief review of the current literature on ATM and present a new clinical case with histopathological, immunophenotypic, and molecular investigations.

Animal-type melanoma: dog or wolf? A review of the literature and a case report

The human animal type melanoma (ATM) is a rare subtype of melanoma characterised by the proliferation of pigmented dermal epithelioid and spindled melanocytes. However, this variant of melanoma is still lacking a precise nosography definition and classification for the difficulty to be distinguished from other more common melanocytic lesions, as well as for its peculiar biological behaviour. On the other hand, the contribution of scientific literature to this issue is fragmented and limited to the description of very few cases. Starting from the presentation of a case with abnormally aggressive clinical features, here we revisit the current knowledge on ATM from its dermatologic patterns, epidemiology, demography and histopathology to the clinical management. Peculiar accuracy has also been reserved to several histopathologic criteria, which are critical for the differential diagnosis from other melanocytic diseases in junction with molecular data deriving from recent cytogenetic and mutational characterisation of this tumour.

Metastatic Blue Nevus-Like Melanoma Detected by Liquid-Based Catheterized Urine Cytology

Primary or metastatic malignant melanoma can mimic benign blue nevus in rare cases, making the diagnosis challenging. Herein, we report an exceptionally rare case of blue nevus-like melanoma and its blue nevus-like metastasis which was detected by catheterized urine cytology. The patient presented with blue-colored papuloplaques on his temple which were diagnosed as blue nevus-like melanoma on punch biopsies. While he was admitted for administration of chemotherapy, hematuria was detected. Catheterized urine cytology revealed singly scattered oval to spindle-shaped pigmented cells with a moderate degree of variation in shape and size. Many of them had small nuclei with indiscernible to inconspicuous nucleoli while only a few cells showed nuclear enlargement and nuclear hyperchromasia, which could be diagnostic pitfalls. Most of the cells on the smear were positive for HMB45 immunostaining, which confirmed the diagnosis of metastatic blue nevus-like melanoma. To the best of our knowledge, the present case is the first report describing cytomorphologic findings of blue nevus-like metastasis of melanoma in the urine specimen.