Twenty-one pathologic and five clinical features of Stage I and II invasive breast cancers from 620 patients enrolled in National Surgical Adjuvant Breast Project Protocol B-04 were analyzed to determine their predictive value for 15-year survival. Ten pathologic features had a statistically significant univariate prognostic relationship with long-term survival. These were analyzed further using a Cox regression model that found only the number of nodal metastases (0, 1-3, 4-9, or 10+), tumor size (< or = 2.0 cm versus 2.1-4 and 4.1 + cm), and the presence or absence of nipple involvement to be significant independent prognostic discriminants. Combinations of these three characteristics modestly increased their individual prognostic value. Differences in the findings in this study from those observed in the same patient population at 5 and 10 postoperative years and their relationship to other markers detected by ancillary pathologic techniques briefly are discussed.