Non-inflammatory skin involvement in breast cancer, histologically proven but without the clinical and histological T4 category features.

Background: The study evaluates characteristics and prognostic significance of breast cancer with histologically proven non-inflammatory skin involvement but without the clinical and histological features that are mandatory for inclusion in the T4 category.

Methods: We compared retrospectively the clinical course of 55 patients with this clinico-pathologic entity to the outcome of a control group of 309 consecutive patients with tumors of the same size but without skin involvement. The median follow-up time was 6.6 years in the study and 8.4 years in the control group. Two subsets were analyzed: (A) 1.1-2.0 cm (T1c); (B) 2.1-5.0 cm (T2).

Results: The distribution of TNM stages within Study Group A was: Stage I: 28.6%, Stage II: 61.9%, Stage III: 9.5%. The distribution within Study Group B was: Stage II: 67.7%, Stage III: 23.5%, and Stage IV: 8.8%. Differences in disease-specific survival (DSS) between study and control groups were not significant. In multivariate analysis, skin involvement was not a significant variable, while lymph node involvement was found to be significant for worse outcome (Group A: HR=3.99 [1.33-12.05], P=0.014; Group B: HR=2.37 [1.37-4.08], P=0.002).

Conclusion: Breast carcinomas with histologically proven skin involvement without the clinical and histological correlate are a heterogeneous group of cases, but the majority of the patients have Stage I/II disease. While lymph node involvement had a most significant effect on DSS, skin involvement was not a significant prognostic factor. Physicians must be aware of this clinico-pathologic entity in order not to misclassify these cases as T4 and consider them falsely as being locally advanced breast cancer.