[Benign and malignant breast tumors with squamous cell differentiation].

Three epidermal tumors with squamous celled differentiation are described. Two appeared as epidermoid cysts, the other was a squamous cell carcinoma in a 100 year old female patient. Epidermoid cysts of the breast are rare compared to lesions occurring in other regions of the human body. They are important, since malignant transformation is possible in 0.5 to 19 per cent of the patients. The mode of origin of squamous cell carcinomas is either metaplastic change in duct epithelium of the nipple or transformation of fibroadenomas or other, malignant tumors. Preoperative differentiation between benign and malignant epithelial cysts is almost impossible. Therefore local excision is the best treatment, since benign cysts, treated only by needle aspiration usually recur. Malignant cysts are best treated by radical amputation, because irradiation and chemotherapy are ineffective in the treatment of squamous celled lesions.