Differentiation of tumours of ductal and lobular origin: I. Proteomics of invasive ductal and lobular breast carcinomas.

The vast majority of invasive breast tumors are ductal and lobular breast carcinomas. Despite the many similarities, some clinical follow-up data and the patterns of metastases suggest that these histological subtypes of breast cancer are biologically distinct. Few papers, however, describe immunohistochemical markers useful for differentiation of these carcinomas. Many investigations suggest that E cadherin protein expression is lost in lobular but not in ductal carcinoma. The absence of E-CD, as a partial loss of epithelial differentiation, may account for the extended spread of lobular carcinoma in situ and the peculiar diffuse invasion mode of invasive lobular carcinoma. Some investigations report the significance of E-CD associated proteins alpha-, beta-, gamma-catenin expression, as well as the usefulness of cytokeratins 5, 6, 8, 7 and thrombospondin in differentiating histological types of breast invasive carcinomas. Several reports have suggested the possibility that invasive ductal and lobular cancers differ with respect to expression of antigens involved in proliferation and cell cycle regulation. It has been shown that vascular endothelial growth factor expression, also the expression of maspin, a tumour suppressor gene product, is higher in ductal, than in lobular carcinoma. Expression of NKX3.1, a member of the NK-class of homeodomain, is highly restricted and is found primarily in lobular carcinoma. Some histological and immunohistochemical characteristics of pleomorphic lobular carcinoma are also discussed.