Classification of nevomelanocytic neoplasia continues to be a challenging problem. In part, this reflects the derivation of these tumors from the neural crest. Like other neural crest-derived neoplasms, the biologic behavior cannot always be extrapolated from cytology alone. Hence, other factors, such as growth pattern, mitotic activity, and host response, play a role in prediction of aggressiveness or lack thereof. Fortunately, most nevomelanocytic neoplasms can be classified into benign nevi or malignant melanomas. However, a group of nevomelanocytic neoplasms remains that cannot easily fit into benign or malignant categories.
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