Skin involvement and breast cancer: Are T4b lesions of all sizes created equal?

Background Nonmetastatic, noninflammatory, invasive breast cancers with skin involvement (SI) are classified as T4b, regardless of size. This study evaluated disease-specific survival (DSS) to determine whether size should be considered for these lesions rather than grouping them all into stage III. Study Design Surveillance, Epidemiology, and End Results data linked to Medicare claims were reviewed. Skin involved and non-SI tumors were reclassified using the American Joint Committee on Cancer, 7^th edition groupings using tumor size and nodal involvement alone without considering SI (neostage). Disease-specific survival was adjusted for demographics, histology, and treatment using competing risk methods with propensity score-based weighting and bootstrap standard errors. Results Among 924 SI patients diagnosed between 1992 and 2005, tumors were 0.1 to 2.0 cm, 2.1 to 5.0 cm, and >5.0 cm in 11.6%, 51.1%, and 37.3% of patients, respectively. There were no nodal metastases in 22.3%, 1 to 3 positive nodes in 31.7%, 4 to 9 positive in 28.6%, and ≥10 positive in 17.4% of patients. For SI patients, adjusted 5-year DSS was 95.8% (95% CI, 95.6-96.0) for neostage I, declining progressively to 36.4% (95% CI, 33.8-39.2) for neostage IIIC patients. Adjusted 5-year DSS for SI and non-SI tumors (n = 66,185) was similar for neostage I, IIA, and IIB, and markedly lower for IIIA and IIIC. Adjusted DSS for SI IIIA was similar to non-SI IIIC. Conclusions Noninflammatory SI breast cancers have widely varied DSS that differs by tumor size and nodal involvement and therefore should not all be stage III. Skin involvement should be subordinate to T and N groupings to classify SI with non-SI lesions having similar prognoses.