ABSTRACT
Animal-type melanoma (ATM), also called melanoma with prominent melanin synthesis or pigment synthesizing melanoma (PSM), is a very rare distinctive clinicopathologic variant of malignant melanoma. It clinically appears as a heavily pigmented, dark-brown, blue or black plaque or nodule. Histopathologically it is characterized by a predominantly intradermal deeply pigmented melanocytic lesion composed of heavily melanized spindle, dendritic or epithelioid cells with some degree of cytological atypia in the background of numerous melanophages. It is a rare histopathologic variant of melanoma so termed because of prominent melanin production and its similarity to a variant of melanoma seen in gray horses. It has potential for aggressive behavior but seems to have a much more indolent course than ordinary melanomas of the same depth of involvement.
