The following is a discussion of less common variants of malignant melanoma (MM). Distinct variants are defined not only to aid in the diagnosis of melanoma but also because proper diagnosis of many variants impacts prognosis and therapy.Malignant melanoma is diagnosed with histologic features including symmetry, circumscription, pattern of growth in the epidermis, degree of cytologic atypia, and pattern of growth in the dermis. These are easily applicable to the more common superficial spreading type of MM. Most diagnoses of MM are based on the evaluation of routine hematoxylin and eosin (H & E)-stained sections and consist of pattern recognition. Less common variants of MM or newly described variants with different patterns may be difficult to recognize. Some variants of melanoma may have patterns with some features similar to benign nevi. Therefore, knowledge of these variants is needed to ensure that the dermatopathologist recognizes all MM.
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