Mitotic figures in sweat gland adenomas

Mitotic rates (mitotic figures per 10 400X fields) were determined for 115 sweat gland adenomas. The observations were also combined for all lesions within each category of adenoma. The combined mitotic rates of spiradenoma, cylindroma, syringoma, and chondroid syringoma were each less than 1.0. Individual lesions within these categories often lacked mitotic figures. With the exception of 1 chondroid syringoma, none of the individual lesions within these groups had mitotic rates exceeding 2.0. The combined mitotic rates of acrospiroma and hidradenoma papilliferum were 1.6 and 1.52, respectively. Twenty-five percent of the acrospiromas had mitotic rates exceeding 2.0 (maximum 7.5). Mitotic figures were concentrated in specific cell populations, particularly in acrospiromas and chondroid syringomas. The potential for cell division appeared to be reduced or lost in areas of increased cytologic or structural differentiation. A review of the literature indicates that there can be overlap between the mitotic rates of sweat gland adenomas and those of carcinomas.