We analyzed retrospectively the relationships and the prognostic significance of four anatomopathological features (elastosis, fibrosis, necrosis, inflammatory cell reaction) of the primary tumor in a series of 1,457 cases of infiltrating ductal carcinoma observed at our institution from January 1978 to December 1991. Necrosis, elastosis, fibrosis and inflammatory cell reaction were strongly associated among themselves (all p < 0.0001), the only exception being necrosis and elastosis. Necrosis was significantly related to tumor size (odds ratio [OR] = 5.40, p < 0.0001) and tumor grade (OR = 2.22, p < 0.0001). Univariate analysis showed that the presence of necrosis and cell reaction were significantly related to worse survival (p < 0.0001 and p = 0.03, respectively). Multivariate analysis, including the four variables plus nodal status, tumor size, grading, adjuvant therapy, age and first order interactions, revealed that greater tumor size (p < 0.0001), positive nodal status (p < 0.0001), higher histologic grade (p < 0.0001) and presence of inflammatory cell reaction (p = 0.0007) independently worsened survival. On the other hand, adjuvant therapy had a significant independent role in preventing deaths (p = 0.03). The only first-order interaction retained in the model was that between grading and cell reaction (p = 0.002). Cell reaction had a different prognostic behaviour in the groups G1-G2 and G3: in the former group, survival was worse (p = 0.0001) when the inflammatory cell reaction was present. In conclusion, we demonstrate that cell reaction is an independent prognostic factor in the G1-G2 subgroup of patients, and propose a hypothesis as to the role of cell reaction in primary breast cancer.