Encapsulated papillary carcinoma of the breast: A clinicopathological study of 49 cases

Background: Encapsulated papillary carcinoma (EPC) has been considered as a variant of ductal carcinoma in situ. Recent studies suggest that EPC could be invasive, as it often lacks myoepithelial cells (MECs) at their periphery. The current study was performed to investigate the biological features of EPC. Methods: Forty-nine EPC patients admitted to the Tai׳an Central Hospital and Qilu Hospital of Shandong University from January 2004-December 2014 were included in this study. We retrospectively analyzed the clinicopathological findings, the presence and distribution of MECs, as well as the outcomes. Results: The mean age at diagnosis was 68.5 years. The mean tumor size was 2.0 cm. MECs were completely absent in all the 49 cases. Most tumors were estrogen receptor and progesterone receptor positive (95.9%). Human epidermal growth factor receptor 2 1+ immunoreactivity was seen in only 8 cases. Twenty-five patients underwent lumpectomy and 24 underwent mastectomy. Thirty-nine received evaluation of lymph node (LN), and 3 (7.7%) patients had LN involvement. Follow-up information was available in 29 patients (8-104 months, mean 47 months), among which 5 developed local recurrences and 2 distant metastases. Conclusion: EPC is an indolent invasive carcinoma with biological features between in ductal carcinoma in situ and invasive carcinoma, with predominance of the latter. EPC rarely showed LN involvement and was characterized by favorable prognosis. EPC can be treated with adequate local therapy and hormonal therapy, whereas the benefit of radiation after lumpectomy remains uncertain.