IMMUNOHISTOCHEMICAL PROFILE OF INVASIVE LOBULAR CARCINOMA OF THE BREAST - PREDOMINANTLY VIMENTIN AND P53 PROTEIN NEGATIVE, CATHEPSIN-D AND ESTROGEN-RECEPTOR POSITIVE

Vimentin, p53 protein and cathepsin D positivity were assessed by immu nohistochemistry, and oestrogen receptor (ER) by an enzyme immunoassay , in invasive lobular carcinomas (LC) of the breast. While vimentin wa s positive in only 5% (3/57) and p53 protein was positive only in 3% ( 2/63), cathepsin D was expressed in 86% (48/56) and ER in 78% (25/32). Classical LC were negative for p53 protein and all except one were ca thepsin D positive. These results are in contrast to invasive ductal b reast carcinomas (DC), where the reported average incidence of vimenti n and p53 protein is much higher (19% and 33% respectively) and that o f cathepsin D and ER lower (63% and 67% respectively). Thus lack of ex pression of vimentin and lack of p53 positivity together with high inc idence of expression of cathepsin D and ER are more often associated w ith lobular than with ductal differentiation of invasive breast cancer . The results show that LC, distinguished morphologically, can further be defined by its immunohistochemical profile. This in turn may point to underlying biological differences between LC and DC.