Flow cytometric DNA analysis showed a significantly higher S-phase fraction in comedo DCIS than in the subgroup of DCIS tumors without necrosis (P < 0.01 [anova]). A preliminary analysis of disease recurrence and disease-free survival in a large series of 391 cases of pure DCIS showed that of 181 cases of pure comedo DCIS there were 19 local recurrences at the 7-year stage (82% 7-year disease-free survival), with 5 local recurrences in 51 cases of DCIS with necrosis (non-pure comedo) (85% 7-year disease-free survival) and only 6 local recurrences in the 159 cases of the DCIS-without-necrosis subgroup (94% 7-year disease-free survival). The chi 2 value for the frequency of disease recurrence of all cases of DCIS with necrosis (i.e., combining the groups of comedo DCIS and DCIS with necrosis (non-pure comedo)) as compared to DCIS without histological evidence of necrosis was 5705 (df = 2; P = 0.0001), and the chi 2 for disease-free survival of types of DCIS with necrosis as compared to cases without necrosis was 178 (df = 2; P = 0.0001). This analysis indicates that the histological presence of necrosis appears to be a relatively powerful predictor of increased disease recurrence and poorer disease-free survival after treatment for DCIS.