29 September 2020
In the absence of clear interstitial invasion, encapsulated papillary carcinoma (EPC) of the breast may be attributed to an extremely good prognosis if handled similarly to ductal carcinoma in situ (DCIS) with suitable local treatment. Here, we report our experience with a case of EPC of the breast that presented with carcinomatous pleuritis and lymphangitis carcinomatosa postoperatively, which rapidly resulted in a poor outcome. A 67-year-old woman was diagnosed with DCIS of the left breast and underwent left partial mastectomy and sentinel lymph node biopsy. EPC was diagnosed because the pathological examination showed no sign of interstitial infiltration. Postoperative radiation therapy was performed. Five years and 9 months postoperatively, the patient began experiencing cough and shortness of breath on exertion. Imaging showed right pleural effusion and consolidation of the lung field, but nothing suggesting local recurrence in the preserved left breast, local lymph nodes, or opposite breast was observed. Postoperative recurrence of breast cancer, carcinomatous pleuritis, and lymphangitis carcinomatosa were diagnosed based on the results of pleural fluid cytology. One month later, multiple brain metastases were found, and the patient died of the primary disease 5 months after recurrence. After surgery for EPC without clear interstitial infiltration, there was a small possibility of a poor outcome from distant metastasis. Therefore, although distant metastasis is uncommon, regular examination and testing should be performed.