A case of a pure squamous cell carcinoma (SCC) of the breast is a 75 y.o. white female is reported. The cancer was discovered at the clinical exam requested by the patient for a growing mass in the left breast. Mammogram and an ultrasound exam showed a big cystic mass (4 cm x 4 cm) with a liquid content and a small polypoid mass of 0.5 cm x 0.5 cm arising from the inner surface of the cyst. A fine needle aspiration was done and the cytological report was consistent with squamous cell carcinoma. A left modified radical mastectomy was carried out. The skin was not involved and the lymph nodes were negative, and no other cutaneous tumor elsewhere was found. The stage was II (T 2a N o M o). The patient did well and was discharged 10 days post-op and now she is still doing well with no signs of recurrences or metastasis. This cancer should not be confused with a much more largely manifest metaplastic changes in a usual breast cancers. The criteria to define "pure" a squamous cell Ca of the breast are: 1) that no other neoplastic element such as ductal or mesenchymal ones are present in the tumor; 2) that the tumor is independent of adjacent cutaneous structure; 3) that no other distant epidermoid tumor exists in the patient. The origin of this tumor is controversial; it has been stated as arising from dermatoid cyst of the breast, chronic abscesses, complete metaplasia of glandular breast tissue. Despite the rarity of this neoplasia it should be kept in mind that in a cystic mass of the breast in older patient could arise a squamous cell carcinoma.