Differences in pathologic characteristics between ductal carcinoma in situ (DCIS), DCIS with microinvasion and DCIS with invasive ductal carcinoma

In order to further our understanding of pathologic features in various ductal carcinoma in situ (DCIS) related breast ductal cancers, including DCIS, DCIS with microinvasion (DCIS-Mi) and DCIS with invasive ductal carcinoma (DCIS-IDC), a retrospective study including 453 cases of DCIS, 88 cases of DCIS-Mi, and 269 cases of DCIS-IDC was conducted. Statistical analysis showed significant pathological differences were found in DCIS, DCISMi, and DCIS-IDC. Compared with DCIS, DCIS-IDC was significantly more associated with high nuclear grade, large tumor size, high Ki67 index, and lymph node metastasis (all P<0.05). Higher expression of steroid receptors was shown in DCIS-IDC than in DCIS (all P<0.05), but the status of HER2 between the two groups was similar (P=0.269). Compared with DCIS, DCIS-Mi was significantly more associated with high nuclear grade, large tumor size, comedonecrosis, absence of steroid receptors, HER2 overexpression, and high Ki67 index (all P<0.05). These features remain consistently even when compared with DCIS-IDC. According to the immunohistochemistry surrogate classification, the dominant types of DCIS and DCIS-IDC were luminal types (luminal A and luminal B, respectively), while the dominant type of DCIS-Mi was HER2 overexpression. These findings suggest that DCIS-Mi represents a distinct entity, and DCIS with features including high nuclear grade, large tumor size, comedonecrosis, steroid receptors negativity, HER2 positivity, and high Ki67 expression was more likely to have microinvasion than DCIS without these features.