[Breast ductal carcinoma in situ with microinvasion: pathological review and clinical implications]

Recent improvements in the detection of breast cancer at an early stage have resulted in a rising incidence of breast ductal carcinoma in situ with microinvasion. So far, there is no consensus regarding its optimal management. We hereby report on our 10-year single institutional experience in breast ductal carcinoma in situ with microinvasion including pathological reviewing.All consecutive patients treated for a ductal carcinoma in situ with microinvasion at the Institut Claudius-Regaud (Toulouse, France) over a 10-year period were included in this study. We reviewed all available histological materials.Sixty-three patients were eligible for this study. Two patients presented with a lymph node invasion at diagnosis. Each patient benefited from initial surgical management, which consisted either in mastectomy (n=25) or conservative resection (n=37). Axillary exploration was performed in 52 patients (82%). After a median follow-up of 61.3 months [46.9;69], the 5-year overall survival and disease free survival were 98.2 (95% CI=[88.2;99.7]) and 89.5% (95% CI=[76.3;95.6]) respectively. Two delayed invasive relapses occurred leading to one specific death. The pathological review highlighted a trend towards a loss of HR and HER2 expression (9%) in the microinvasive component in comparison with its surrounded in situ carcinoma.The risk of initial lymph node involvement and delayed invasive local relapse deserve an optimal locoregional management including lymph node evaluation. The non-negligible discrepancy's rate between in situ and microinvasive components justifies HR status and HER2 expression assessment on the microinvasive component.