[Metachronous tumors of the breast. Mammographic findings]

In breast carcinoma patients the risk to develop a second lesion in the contralateral breast is two to six times higher than in control subjects. The second lesion is called metachronous and classified among bilateral breast cancers. This kind of lesion affects the patients who were mastectomized for breast carcinoma; it may be a primary lesion, when the histologic type is different from that of the first breast cancer or secondary, when the histologic type is the same as that of the first tumor and the second lesion is therefore a metastasis. This study was made to assess the incidence of metachronous lesions and the average time between the first and the second tumor and to investigate the value of mammographic followup. We selected 375 patients who had undergone mastectomy for different histologic types of breast carcinoma and examined the contralateral breast with mammography 6 months after surgery and then every 12 months, January 1990 through January 1992. Mammography showed metachronous lesions in 23 cases: 15 infiltrating ductal carcinomas, 6 infiltrating lobular carcinomas and 2 in situ carcinomas, the latter with histologic confirmation in the patients operated on for benign breast lesions. The incidence of metachronous tumors was 6%, including both the primary and the metastatic lesions; the average time between the first and the second tumors was 20 months. Mammography allowed metachronous lesions to be diagnosed in a very early stage, much earlier than in other studies not including mammography. Prognosis is definitely improved by the early diagnosis of primary breast cancer, when no metastatic spread is present, and also in case of primary metachronous lesions, which are very uncommon.