Agminate and plaque-type blue nevus combined with lentigo, associated with follicular cyst and eccrine changes: a variant of speckled lentiginous nevus.

Agminate and plaque-type blue nevi are rarely described. We report the occurrence of such a type of blue nevus associated with eccrine changes and a follicular cyst all arising on a macular brown background in a 38-year-old man. The patient presented numerous blue papules and a plaque, overlapping a light tan patch present since birth, on his left thigh. In addition, within the plaque, 3 papules, discharging at intervals a serous fluid, were present. Since the lesion hardened and enlarged, it was surgically excised. Histologic findings revealed a lentigo pattern of the epidermis, corresponding to the light tan macular background and a plaque-type blue nevus, and areas of eccrine ductal proliferations with a ruptured follicular cyst. The association of agminate and plaque-type blue nevus, arising on a light brown patch of lentigo, might represent a variant of speckled lentiginous nevus. Eccrine proliferations may be reactive in nature or represent a more complex hamartomatous lesion. The possibility of malignant transformation and the recent enlargement of the lesion caused by the ruptured follicular cyst convinced us to carry out a wide surgical excision.