Neuroendocrine differentiation in breast carcinoma: clinicopathological features and outcome

AIMS: Primary neuroendocrine (NE) breast carcinoma (BC) is an entity with a wide range of prevalence and poorly defined clinical behavior. We evaluated the prevalence, clinicopathological features and clinical outcome of NEBC. METHODS AND RESULTS: Immunohistochemical staining for synaptophysin and chromogranin A was performed on whole sections from 1232 consecutive cases of invasive BC. We divided NEBC in focal (10-49% positive cells) and diffuse (≥50% positive cells) and compared the outcome of patients with NEBC with strictly matched non-NEBC. A total of 128 BC showed NE differentiation (10.4%): 84 diffuse (6.8%) and 44 focal (3.6%). NE differentiation showed a significant association with T4 stage (P=0.001), solid-papillary and mucinous histotype (P