ABSTRACT

Microinvasive breast cancer (MIBC) is a rare tumor. Despite of its good prognosis, which is similar to in situ breast cancer, its management is still similar to invasive tumors. The aim of this study is to assess the prognostic implications of SNLB in MIBC patients and to evaluate the possibility for surgical de-escalation in these patients.
Methods: A multicentric retrospective study including all patients with MIBC diagnosis who underwent surgery from 2012 to 2022 is carried on. Seven different Italian Breast Units contributed to the study. Preoperative, intraoperative and post operative data were taken into account, including final histological report with tumor staging and oncological outcomes.
Results: 261 patients were included. The metastatic rate of sentinel lymph node biopsy (SLNB) was 9.2 % (2.3 % macrometastasis, 6.9 % micrometastasis or isolated tumors cells). Multifocal lesions (p-value: 0.045; OR:1.730), and the absence of hormone receptors (p-value: 0.018; OR:3.658) are all predictors of sentinel lymph node metastasis, while a Ki67 proliferation index <20 % associates with a low risk of nodal metastasis (p-value: 0.035; OR:0.289). Five-years loco-regional recurrence in patients with metastatic sentinel lymph node was comparable to the non-metastatic ones (95.7 % vs 94.1 %; p-value: 0.951). Cox Regression analysis identifies age at diagnosis as a predictive factor of locoregional recurrence at five years (OR 0.831 95%CI: 0.721–0957, p-value: 0.010).
Conclusion: MIBC has a favorable prognosis and very low macrometastatic sentinel lymph node rates. The omission of SNLB in patients with MIBC provides a similar overall survival rate, therefore SNLB should be reserved to younger patient with preoperative radiological or clinical suspicion of metastatic lymph nodes.