A 57-year-old woman with a history of interstitial pneumonia since 5 years ago was diagnosed with a 10mm diameter tumor during the medical examination and consultation at the hospital. The tumor was palpable in the AC area of her right breast. An ultrasonography showed an irregular-shaped mass. A vacuum-assisted biopsy was performed, and the pathologicaldiagnosis was suspicious for malignancy. Then, we performed an excisionalbiopsy and confirmed the definitive diagnosis of invasive ductalcarcinoma. However, surgicalmargins were positive on the skin and lateralside; therefore, we conducted a two-stage surgery. Interstitialpneumonia was in the active phase, and she was administered sufficient amount of immunosuppressive drugs. Therefore, we performed additionalresection under localanesthesia, not generalanesthesia. Interstitial pneumonia did not worsen perioperatively, and the postoperative course was uneventful. Surgeries performed while the patient is administered with immunosuppressive drugs may cause infections and delayed wound healing. Thus, perioperative complications should be carefully considered.