Introduction Breast cancer (BC) is the first cancer in women. The diagnosis, management and prognostic impact of ipsilateral synchronous multiple breast cancers (ISMBC) remain a dilemma in the scientific literature. We aim to study the specific clinical and pathological features of this entity.

Methods A retrospective study was conducted at our institution over 11 years (2010–2020). We recruited all cases of ISMBC. We difined ISMBC as all cases of multifocal BC (multiple foci present in the same quadrant of the breast) and/or all cases of multicentric BC (multiple foci located in different quadrants) excluding bilateral synchronous BC.

Results We recruited 159 cases of ISMBC representing 6.1% of all BC. The mean age was 51.6 years [26–85.The sensitivity of breast MRI was superior to that of ultrasound-mammography in the detection of BC multiple locations. Invasive ductal carcinoma was the predominant histological type. The mean histological tumor size was 31 mm ± 16.6 mm. The most common SBR grade was grade II. There was a predominance of luminal subtype B. MAstectomy was performed in 81.8% of patients and 83% had axillary lymph node dessection. Locoregional recurrence was 5.96%. Distant metastases were found in 7.54%. The 5-year OS and DFS were 87.4% and 88.6%, respectively. In multivariate analysis, SBR grade was a significant prognostic factor for OS and DFS.

Conclusion/Implications The current ISMBC clinical and pathological staging system is perfectible in order to custumize the treatment options to the reality of the disease especially regarding breast surgery.