Sweat gland carcinoma with syringomatous features: a light microscopic and ultrastructural study.

A 76-year-old man presented with a 10-year history of a slowly enlarging lesion of his upper lip. An excisional biopsy revealed a diffusely infiltrating, well-differentiated, sweat gland carcinoma with syringomatous features. The ultrastructural characteristics corresponded to those described for benign syringoma and normal eccrine ducts. A review of the literature emphasized the extreme rarity of this lesion. Sweat gland carcinomas tend to have an indolent history but often manifest aggressive behavior at the time of clinical presentation. The preponderance of anaplastic lesions accounts for a generally unfavorable prognosis.