Encysted Papillary Carcinoma of the Breast (EPC): A Follow-up Study to Investigate the Role of Sentinel Lymph Node Biopsy

Abstract

Background: Encysted papillary carcinoma (EPC) is a rare breast neoplasm that mainly affects postmenopausal women. The purpose of this study was to examine whether a sentinel node biopsy would be deemed necessary in patients with a diagnosis of EPC and to determine if evidence of invasiveness can be diagnosed on a core needle biopsy with sufficient confidence to guide decision making for upfront axillary SLNB.
Methods: The available data of patients with EPC of the breast were reviewed at a tertiary breast cancer unit over a period of 10 years (2009-2019) and the concordance between core needle biopsy and final histology was assessed. We also carried out a detailed review of the available literature to inform best practice guidance for management of the axilla.
Results: During the study, a total of 37 EPC patients were identified, of whom 10 were excluded as they declined further treatment, providing us a study sample of 27 patients. The median age at diagnosis was 72 years (range 47-97) and the vast majority of patients (96%) were Estrogen Receptor (ER) positive. Of the 27 patients treated, 17 (63%) underwent a diagnostic axillary Sentinel Lymph Node Biopsy (SLNB). On the final histology, 13/27 (48%) proved to have invasive disease. A total of 5 (18%) patients had evidence of metastasis in the axillary nodes, of whom only 7% had macro-metastatic disease that warranted further axillary treatment. None of the treated patients had evidence of recurrence or distant metastatic disease, to date (median of 5 years of follow up).
Conclusions: Encysted papillary carcinoma is associated with a low incidence of axillary node involvement. SLNB should only be carried out when there is evidence of invasive cancer. An algorithm was developed to help guide management of the axilla in cases diagnosed with EPC on diagnostic core needle biopsy.