A 49-year-old premenopausal woman with stage 1 breast carcinoma underwent left quadrantectomy with axillary dissection in 1992. The tumor was 0.7×0.5 cm. Histopathologically, this was a pure tubular carcinoma without lymph node metastasis or lymphatic or vascular invasion. Although the surgical margin was pathologically negative, atypical ductal hyperplasia was present close to the cut margin's edge. Neither adjuvant chemotherapy nor radiotherapy had been given after the operation. Approximately 5 years after the first surgery, she had a local recurrence in the vicinity of the operative wound. There was no clinical evidence of distant metastasis. A salvage mastectomy was performed. Histopathological examination revealed that the second tumor was an invasive ductal carcinoma, histological grade 2, with extensive intraductal component. It was difficult to determine whether this was a true in-breast recurrence or a second primary cancer. Overexpression of p53 and c-erbB-2 was observed in the second tumor. Estrogen receptor and progesterone receptor were both negative. No postoperative chemotherapy was given. Multifocality and atypical ductal hyperplasia were observed in 7 (87.5%) and 6 75% of 8 patients, respectively, with tubular carcinoma between 1991 and 1997 at the National Cancer Center Hospital. Coexisting disease associated with tubular carcinoma suggests that radiotherapy may be an important component of breast conservation treatment to prevent local recurrence in this type of tumor.