Cathepsin-D (CathD) is an aspartyl lysosomal protease expressed in all tissues that might play a role in antigen processing, cell proliferation and tissue renewal, and activation of different pro hormones. The aim of our study was to compare the expression of CathD in most common breast tumors and tumor-like breast lesions. The study includes 21 patients with histologically verified breast lesions (adenosis, ductal hyperplasia, fibroadenomas, and different types of invasive carcinoma). We investigated the cathepsin-D expression in these breast lesions using immunohistochemistry (IH; paraffin-embedded tissues). Cathepsin-D staining within each lesion was assessed by estimating the area of the objects and the medium pixel intensity per object, as the integrated optical density (IOD). The immunostaining was more obvious in breast invasive carcinomas and macrophages. The reaction in tumor tissue was heterogeneous with little variation of staining intensity in positive tumor cells. Adenosis had the maximum area/signal intensity from all studied breast benign lesions (p<0.001, Student t-test). The general tendency (all benign lesions, lobular carcinomas and G3 ductal invasive carcinoma) was a more prominent representation of the cellular compartment. In the G3 ductal invasive carcinoma-type, the group of patients with metastases had a stronger expression in the cellular compartment. These results suggest that CathD expression was strongest in malignant than in benign breast disease, the positivity being present in both epithelial neoplastic and stromal cells. We also conclude that our procedure in IOD measurement is prone to less subjective-related biases, and thus more accurate and constant than other methods employed by other authors.