According to the TNM Supplement, only breast carcinoma with macroscopic ‘classic’ skin changes (e.g., edema, peau d'orange, ulceration) should be placed in the T4 category; the classification of tumors with histologically proven skin involvement but no clinical skin changes or only discreet changes should be based on the size of the tumor (T1–3). To the authors' knowledge, no data supporting these recommendations have been reported to date.
Seventy-six patients with noninflammatory breast carcinoma and histologically proven skin involvement were classified based on the degree of their skin involvement. Fifty patients (66%) presented with clinically obvious skin involvement (Group A), and 26 patients (34%) had breast carcinoma with histologically proven skin involvement but without clinical skin changes (Group B). Reclassification was undertaken to assess the malignant potential of tumors independent of the morphologic parameter ‘skin involvement’.
Patients in Group A presented significantly more frequently with extensive disease at regional or distant sites (Stages IIIC and IV; P = 0.009). The clinical outcome of patients in Group B was significantly more favorable (P = 0.0003). The adjusted 3-year survival rates in Group A and Group B were 46.7% and 92.3%, respectively, and the 5-year rates were 38.1% and 83.7%, respectively. Patients in Group B were found to have significantly better (P = 0.036) distant recurrence–free survival (DRFS) rates. The DRFS rate at 3 years was 63.6% in Group A, compared with 91.7% in Group B, and the DRFS rate at 5 years was 56.9% in Group A, compared with 82.0% in Group B. Using a cutoff point of tumor size = 3 cm, similar findings were made.
Both study groups exhibited distinct clinical entities with significant differences in clinical course and prognosis. Cases with histologic skin involvement, relative to those with classic skin involvement, were found to have much less malignant potential. This corroborates the recommendation that cases with only histologic skin involvement should not be placed in the T4 category of the TNM classification. Cancer 2004. © 2003 American Cancer Society.