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.