Background: As the incidence of ductal carcinoma in situ (DCIS) is increasing, it is necessary to make a guideline for the pathological examination and diagnosis of DCIS, by creating criteria based on clinical and biological aspects of the disease.
Method: We collected biopsy specimens originally diagnosed as benign lesions, from patients who subsequently developed invasive carcinoma in the ipsilateral breast. The histology of the biopsy specimens was re-evaluated principally according to the 1995 Philadelphia Consensus on DCIS. Histopathological agreement on each biopsy specimen was made by the JBCS Study Group members under a multiviewer microscope. In the course of making conclusive agreements among the pathologists, we developed a consensus for the histopathological diagnosis of DCIS, especially non-comedo types.
Results: DCIS is defined as a carcinoma of ductal epithelial origin, without any evidence of stromal invasion. It is necessary to note the methods of pathologic examination required to diagnose DCIS. Stromal invasion is an important prognostic factor, and should be diagnosed with caution. Classification of proliferative ductal lesions as benign or malignant (DCIS), the subtype of DCIS (nuclear grade, architecture, and necrosis), and the histological grading of DCIS are proposed and recommended.
Conclusion: Although we have made a new proposal according to current concepts, there are still several unresolved problems. Thus further examination and modification will be necessary in the future.