Spontaneous apoptosis by in situ detection of DNA fragmentation (DNAf) was investigated in breast invasive ductal carcinoma (IDC) frozen samples removed from 61 untreated patients. The incidence of DNAf was low in carcinoma cells and was mainly detected in the stroma. In the stroma at a distance from carcinoma cells, DNAf was inversely related to estradiol plasma level variations (p=0.01), indicating that it probably remained under physiological hormonal regulation. In the stroma adjacent to carcinoma cells, DNAf was correlated to tumor progression parameters such as the presence of a comedo intra ductal carcinoma (DCIS) component (p=0.001) and axillary lymph node metastasis (p=0.002), suggesting that this stromal compartment more probably represented a tumoral component closely associated to epithelial tumor cells. Therefore, the detection of DNAf in the adjacent stroma of breast carcinoma could help to predict progression in non invasive tumors and also in invasive tumors in those patients without lymph node invasion.