Breast skin ulceration in de novo metastatic breast cancer: incidence, predictors, and patterns of occurrence.

BACKGROUND: This study aimed to identify factors associated with breast skin ulceration (BSU) and to describe its timing and patterns of occurrence in de novo metastatic breast cancer (MBC). METHODS: We conducted a retrospective cohort study including women diagnosed with de novo MBC between 2008 and 2019 at Institut Curie. Clinical, pathological, and treatment-related data were extracted from the ESME database, a large, nationwide French real-world database dedicated to metastatic breast cancer. The primary endpoint was the presence or development of BSU. Secondary endpoints included progression-free survival (PFS) and overall survival (OS). RESULTS: Among 669 patients with de novo MBC, 53 (7.9%) presented with or developed BSU. Ulceration was present at diagnosis in 50 cases (94%), whereas secondary BSU during follow-up was rare (n = 3). All secondary BSU occurred in non-operated inflammatory tumors (T4d), and no secondary BSU was observed in non-inflammatory disease. Larger tumor size, inflammatory presentation, and higher metastatic burden were associated with BSU. In unadjusted analyses, BSU was associated with shorter PFS and OS, but this association was no longer significant after multivariable adjustment. CONCLUSIONS: Breast skin ulceration in de novo MBC is an uncommon event that primarily reflects aggressive inflammatory tumor behavior rather than inadequate locoregional management. Secondary BSU is exceptionally rare and confined to inflammatory tumors. Systematic routine surgical intervention solely to prevent ulceration appears unjustified in non-inflammatory disease.