Breast Microinvasive Carcinoma With Different Morphologies: Analysis of Clinicopathologic Features of 121 Cases

To investigate the clinicopathological features of patients with breast microinvasive carcinoma (MI).

The clinical data of 121 cases with breast MI were retrospectively collected. The whole tumor in each case was stained with hematoxylin and eosin (H&E) for pathological evaluation. The relationships among size of tumor, histological grade, tumor-infiltrating lymphocytes (TILs), the number of MIs, type of MI, and lymph node metastasis were analyzed.

It was revealed that 86% of the cases had high-grade ductal carcinoma in situ (DCIS) and 63.6% had multiple MIs. The larger size of the tumors, the higher the grade of DCIS, the more the number of MIs; 3.3% of cases had rich TILs (lymphocyte/stroma > 30%) in the DCIS, and 26.5% had rich TILs in MIs. The type A of MIs is characterized by single cells and small clusters of solid cells. Tumor cells in type B of MIs can form glandular ducts. Formal grading of microinvasive is challenging/impossible due to its limited size precluding a representative mitotic count. But nuclear grade and tubule (differentiation) grades can be reported. In addition, 72.7% of cases had type A of MIs and 27.3% of cases had type B of MIs. Type B was found to be highly accompanied by moderate-grade DCIS. Only 6.6% of patients with MI had lymph node metastasis, which was mainly related to MIs with less TILs.

Breast MI is easy to occur in high-grade DCIS, and multiple infiltration foci may be observed in case with tumor size of higher than 3.5 cm. Microinvasive carcinoma with poor TILs maybe a risk factor for lymph node metastasis in patient with DCIS-Mi.