Primary Well-Differentiated Neuroendocrine Tumor of the Breast: A Case Report and Literature Review.

BACKGROUND Primary breast neuroendocrine neoplasms (NENs) are extremely rare, comprising 1-5% of diagnosed breast cancers. The goal of this paper is to describe the current literature on these cancers, along with treatment options and survival data from prior studies. CASE REPORT A 61-year-old woman presented with a palpable lump in the breast, which upon biopsy was proven to be a primary breast neuroendocrine tumor. This was treated with breast-conserving surgery with sentinel lymph node dissection, followed by adjuvant radiation. She refused anti-estrogen therapy, and 2 years later she presented with metastatic disease, chose not to receive any additional treatment, and died. Several retrospective analyses have illustrated that breast neuroendocrine tumors have a slightly worse prognosis compared to invasive ductal carcinomas (IDCs) when stratified by stage. However, most of the studies had small sample sizes, which makes interpretation of data from these studies difficult to generalize to the overall population of breast NENs. CONCLUSIONS Routine testing for neuroendocrine markers could identify a larger population of neuroendocrine tumors (NETs). Currently, because of the rarity of these tumors, prospective trials are not available to study them as a distinct entity to evaluate and optimize treatments. Reports indicate that these tumors have overall inferior survival compared to IDCs. Further studies are needed to evaluate this rare entity to improve patient outcomes.