Immunolocalization of aromatase in human breast disorders using different antibodies

Immunolocalization of aromatase can provide important information about the status of intratumoral aromatase of human breast. We have performed immunohistochemistry of aromatase in surgical pathology specimens of human breast disorders using monoclonal and polyclonal antibodies. Both antibodies yielded satisfactory results in immunostaining of aromatase in normal placenta and normal cycling human ovaries. In human breast disorders, immunostaining or aromatase using monoclonal antibodies can only demonstrate immunoreactivity following antigen retrieval. Immunoreactivity can be detected in both carcinoma and stromal cells but nuclear immunoreactivity, which may be represent artefactural changes, can be detected in both normal and neoplastic breasts. Immunostaining using polyclonal antibody revealed aromatase immunoreactivity in cytoplasm of adipocytes, fibroblasts, vascular wall cells and Schwann cells but intense immunoreactivity was detected in adipocytes adjacent to carcinoma invasion in 68/82 carcinoma cases and stromal cells around carcinoma nest in 58/82 cases. Strong aromatase immunoreactivity was detected in 7/69 benign proliferative breast disorder, 5 of which were sclerosing adenosis. Aromatase immunoreactivity was also detected in carcinoma cells in 7/82 cases but aromatase positive carcinoma cells represent less than 5% of tumor cells in all these cases. These results above indicate that polyclonal antibody is considered to be more suitable for aromatase immunohistochemistry in archival materials of breast disorders but further investigations including easy and reproducible scoring system and production of reliable monoclonal antibodies are required to establish aromatase immunohistochemistry as a reliable method of assessing intratumoral aromatase in human breast disorders.