Tumour markers in breast carcinoma correlate with grade rather than with invasiveness

Ductal breast carcinoma in situ (DCIS) is regarded as a precursor to invasive breast cancer. The progression from in situ to invasive cancer is however little understood. We compared some tumour markers in invasive and in situ breast carcinomas trying to find steps in this progression. We designed a semi-experimental setting and compared histopathological grading and tumour marker expression in pure DCIS (n = 194), small invasive lesions (n = 127) and lesions with both an invasive and in situ component (n = 305). Grading was done according to the Elston-Ellis and EORTC classification systems, respectively. Immunohistochemical staining was conducted for p53, c-erbB-2, Ki-67, ER, PR, bcl-2 and angiogenesis. All markers correlated with grade rather than with invasiveness. No marker was clearly associated with the progression from in situ to invasiveness. The expression of tumour markers was almost identical in the 2 components of mixed lesions. DCIS as a group showed a more 'malignant picture' than invasive cancer according to the markers, probably, due to a higher proportion of poorly differentiated lesions. The step between in situ and invasive cancer seems to occur independently of tumour grade. The results suggest that well-differentiated DCIS progress to well-differentiated invasive cancer and poorly differentiated DCIS progress to poorly differentiated invasive cancer.