The antiapoptotic protein survivin can be detected in most types of malignant tumors, but it is rarely expressed in corresponding normal adult tissues. Therefore, survivin appears to represent a promising diagnostic biomarker. We examined survivin expression in 13 cases of normal breast tissue, 38 cases of fibroadenomas and 80 cases of breast carcinomas by immunohistochemical staining using anti-survivin antibody (DAKO, Clone 12C4). In each section, the intensity of staining, percentage of labeled cells, and the subcellular location of survivin antigen were assessed. Survivin was detected in 4/13 cases of normal breast tissue (30.7%), in 28/38 cases of fibroadenomas (73.7%), and in 67/80 cases of carcinomas (83.8%). Normal breast tissue showed cytoplasmic positivity only. In fibroadenomas, 19 cases (50.0%) revealed cytoplasmic reaction, and in 9 cases (23.7%), small foci of cells with combined nuclear and cytoplasmic location were identified. In carcinomas, cytoplasmic staining was found in 12/80 cases (15.0%), nuclear staining in 10/80 cases (12.5%), and combined cytoplasmic and nuclear staining in 45/80 cases (56.3%). Subcellular location of survivin between benign and malignant lesions revealed significant differences (p<0,001). Our findings point at practical use of survivin detection. We confirm the importance of nuclear staining of survivin antigen in breast carcinoma, which seems to be a notable diagnostic marker for estimation of the degree of neoplasia.