Report about a 46 year old women with granular cell tumor of the breast. Clinical features, mammography and sonography has appearances highly suspicious for breast cancer. Tumorectomy and axillary lymphonodectomy were performed. Estrogen and progesterone receptor both were histochemically and biochemically negative. Estradiol and prolactin levels in serum were normal. Cathepsin D in cytosol was slightly elevated, DNA-flow-cytometry revealed no signs of malignancy. Evident was the high content of protein S100 in cytosol of tumor cells.