Clear cell metaplasia of the breast: a lesion showing eccrine differentiation.

Clear cell metaplasia of the human breast is known to be a benign metaplastic change which has no pre-malignant connotation. Despite its proposed relationship to focal lactational change and to lactating breast, morphological and immunocytochemical features failed to demonstrate a clear relationship between these. Mucin secretion showed a characteristic pattern of granularity, and endocrine differentiation was not present. The mucin and immunocytochemical features suggest a relationship with eccrine sweat glands and a better name would perhaps be 'eccrine metaplasia' to underline the special relationship breast metaplasias have to sweat gland epithelium.