Objectives Ductal carcinoma in situ with microinvasion (DCISM) is rare, < 1% of all breast cancer cases. The histological definition of this entity remains controversial. Due to the inconsistent definition and limited data regarding this breast cancer subtype, there are no clear treatment recommendations.

Methods We retrospectively reviewed the clinical-pathological aspects, the treatments, and followed by a cohort of 17 patients diagnosed with DCISM and microinvasive carcinoma from 2000 to 2017 in our institution.

Results The median age was 52 years old, 58.8% of patients were menopausal, all patients were operated on, 42.2% had conservative treatment, sentinel lymph node dissection was performed in 64.7% of cases with no micro or macro-metastases. Pathological examination found DCISM in 47% of cases (53% of cases were pure microinvasive ductal carcinoma). Comedonecrosis was found in only two cases. Hormonal receptors were positives in 87.9% of DCISM cases. We performed radiotherapy in 47% of patients. Adjuvant chemotherapy was prescribed to 17.6% of patients, and 70.6% of patients underwent adjuvant endocrine therapy. Only one case underwent targeted adjuvant therapy. The Median follow-up was 42 months. We did not notice any relapse or metastasis.

Conclusions The development of screening programs increases the diagnosis of small tumors, especially DCISM. This entity remains with a good prognosis. Better knowledge and evaluation of risk factors of relapse are needed to define adjuvant treatment.