Romanian Journal of Morphology and Embryology 2009, 50(1):31–39 ORIGINAL PAPER Cathepsin-D expression in breast lesion: an immunohistochemical study IULIA BRUJAN 1) , CL. MĂRGĂRITESCU 2) , CRISTIANA SIMIONESCU 2) , D. PIRICI 3) , A. FRONIE 4) , CAMELIA FOARFĂ 2) , A. STEPAN 5) , MARIA VRABETE 1) 1) Department of Physiopathology 2) Department of Pathology 3) Department of Histology 4) Department of Oral Pathology University of Medicine and Pharmacy of Craiova 5) Laboratory of Pathology, No. 1 Emergency County Hospital, Craiova Abstract 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. Keywords: breast, carcinoma, cathepsin-D, immunohistochemistry.  Introduction Breast cancer still remains a major world health problem, being the second leading cause of cancer death in women, exceeded only by lung cancer. It is estimated that breast cancer will affect five million women worldwide over the next decade, and the incidence of the disease is increasing at an average of about 1% per year in industrialized countries and at a greater rate in developing countries [1, 2]. Considerable progress has been made in understanding the mechanisms of breast tumor growth and progression. Over the years, there were studied more than thirteen categories of breast tumor markers, hoping to improve prevention, screening, treatment, and surveillance of breast cancer [3]. One of these breast cancer markers is CathD. This biological marker is a peptidase belonging to the family of aspartic peptidases. Major function of CathD is the digestion of proteins and peptides within the acidic compartment of lysosome [4]. Other physiological effect includes hormone and antigen processing, and breakdown of the extra cellular matrix. In the latest decades, there has been an increasing number of data, describing elevated levels in certain tumor tissues, associated with their progression and metastases [5–7]. The aim of the present study was to compare the expression of CathD in most common breast tumors and tumor-like breast lesions.  Materials and Methods Tissues and histopathological processing Twenty-one formalin-fixed, paraffin-embedded breast tissue blocks from the archive of the department of pathology (No. 1 Emergency County Hospital, Craiova) were included in the current study. All these samples originated from complete resection material. Sections from these paraffin-embedded blocks were stained with Hematoxylin and Eosin (HE). Two experienced pathologists (S.C. and F.C.) without knowledge of the clinical data performed re-evaluation of the HE stained sections. Diagnosis and tumoral grading were performed according to WHO criteria.