Mycosis fungoides with extracutaneous localization in the breast.

We report a patient with mycosis fungoides (MF) and transformation to anaplastic (CD30+) lymphoma, who developed an unusual manifestation in the breast. Cutaneous and extracutaneous tumour cells both showed marked intraepithelial migration, but had distinct expression patterns of epitheliotropism-associated integrins. Intraepidermal and dermal lymphoma cells in the skin expressed most of the integrins that are presumed to be involved in epitheliotropism, such as leucocyte functional antigen-1 (LFA-1), alpha 1 beta 1, alpha 3 beta 1, alpha 4 beta 1 and alpha 6 beta 1. In the breast, most of the extraepithelial tumour cells only expressed the laminin-5 ligand alpha 3 beta 1 (strong) and the collagen ligand alpha 1 beta 1 (weak). However, on the intraepithelial tumour cells in the mammary ducts and glands LFA-1, alpha 4 and alpha E could also be detected. In view of these findings we propose epitheliotropism of the MF cells in the breast to be a multistep process in which tumour cell-epithelial basement membrane (EBM) interaction, predominantly mediated by alpha 3 beta 1 and laminin-5, is the primary event. Adhesion to and subsequent infiltration of the neoplastic lymphoid cells into the EBM may, either directly or indirectly, lead to upregulation and/or activation of other integrins that amplify interaction with epithelial cells.