Prognosis and Clinicopathological Characteristics of Microinvasive Breast Carcinoma

Abstract

In this study, we investigated the prognosis of microinvasive breast cancer in 901 patients with primary unilateral breast cancer, who underwent surgery at our hospital in 2007. We retrospectively analyzed 233 breast cancer tissue specimens (greatest diameter of invasion ≤ 5 mm) ; 134 cases (57.5%) were classified as pTis (non-invasive cancer), 33 (14.2%) as pT1mi (micro-invasive cancer), and 66 (28.3%) as pT1a (invasive cancer, diameter > 1 mm but < 5 mm). The number of patients with positive lymph node metastasis was significantly lower in the pT1mi than in the pT1a group. The median follow-up period was 87 (12-140) months, and only one patient developed distant recurrence in the pT1mi group. The patient did not receive any postoperative medications. Histopathological evaluation confirmed multiple tiny invasive foci. Examination of deep sections of the pathological block revealed coalescence of the invasive foci into a large lesion (diameter > 1 mm), which did not appear in the usual search. We observed no breast cancer-induced mortality and favorable prognosis in all three groups, without any difference in the disease-specific survival rate based on the invasion diameter.