[Smooth muscle hamartoma or nevus of Becker? Apropos of 4 cases].

Theoretically, Becker's melanosis or hairy epidermal nevus and smooth muscle hamartoma are two quite separate entities. In fact, there are cases which could be considered as intermediate. As a matter of fact, a slight underlying smooth muscle hyperplasia can be seen in Becker's nevus; on the other hand, hypermelanosis of the basal layer and hypertrichosis may be encountered in smooth muscle hamartoma. The 4 here reported cases are examples of diagnostic difficulties for which the sometimes not clear-cut limits of these 2 types of lesion can be responsible.