Most cases of DCIS are picked up because of a mammogram that shows calcifications. In most women there is no mass or lump in the breast. The pattern of calcifications is helpful in guiding the surgeon as to where to do the biopsy and in predicting which women will need a mastectomy rather than a lumpectomy

In type I the calcifications are in a small cluster and if all the abnormal calcifications can be removed and the pathology report shows clear margins (no cancer at the edges) then a lumpectomy followed by radiation is ideal. In type II there is a  larger cluster or "cloudburst" of calcifications. These patients may still be candidates for lumpectomy if all the abnormal calcifications can be removed without deforming the breast too much. In young women with a large area of calcifications, many doctors recommend a mastectomy. In type III, the diffuse pattern, a mastectomy is almost always necessary to ensure a high control rate.