Giant eccrine acrospiroma. Four cases of large eccrine acrospiroma (three benign, one malignant) are reported. The benign tumors involved the lower extremities of two women and one man (73 to 89 years of age). The duration of the lesions ranged from 10 to 20 years. The malignant tumor involved the left side of the chest of a 60-year-old man. Its occurrence in a lesion that had been present for 40 years suggested malignant transformation of a pre-existing benign eccrine acrospiroma. Each tumor showed little to no cellular atypia. Mitotic rates (mitotic figures per 10 high-power fields) varied both between and within lesions. Average mitotic rates did not differentiate the benign from the malignant tumors. The most important distinguishing features of large benign eccrine acrospiromas are the relative circumscription, the lack of cellular atypia, and the absence of stromal, perineurial, and angiolymphatic invasion. 