Combined blue nevus‐smooth muscle hamartoma: a series of 12 cases

Abstract

One of the most common types of combined melanocytic nevus is that of a blue nevus with ordinary melanocytic nevus. Blue nevi have also been described in association with non-melanocytic cell types, such as those of neural or mesenchymal derivation. Although there are rare descriptions in the literature of blue nevi with myomatous structures, the specific association of combined blue nevi with smooth muscle hyperplasia has not been reported We review the clinicopathological features of 12 cases of combined blue nevi with smooth muscle hyperplasia. The majority of these lesions occurred on the back of middle-aged patients and were clinically interpreted as melanocytic nevi or melanoma. Histopathologic examination revealed a combined population of 'common' and blue nevus melanocytes with accompanying smooth muscle hyperplasia. In addition to a lentiginous proliferation of melanocytes at the dermal-epidermal junction with variable basilar hyperpigmentation, there were varying degrees of epidermal acanthosis and follicular induction (three cases). We present an unusual hamartoma with features of combined blue nevus and smooth muscle hyperplasia, which has not been previously described.