Tissue microarray analysis as a screening tool for neuroendocrine carcinoma of the breast

Neuroendocrine carcinoma of the breast (NCB) is a fairly recent diagnostic entity added by WHO in 2003. Since then, studies have indicated that NCB potentially displays a worse prognosis than invasive ductal carcinoma. However, due to a lack of standard use of immunohistochemical staining for neuroendocrine markers and the fact that NCB may only show slight neuroendocrine morphology that can easily be overlooked, NCB is often underdiagnosed. Consequently, there is a need for fast and reliable detection method for NCB. Here, we take a first step toward finding an easy way of identifying NCB by investigating the usefulness of tissue microarray (TMA) analysis as a screening tool. We present our findings with regard to sensitivity and specificity compared with whole‐mount sections. The material consists of 240 cases of breast cancer divided into 20 TMA blocks that were all immunohistochemically stained for the neuroendocrine markers chromogranin A and synaptophysin. Cases positive in more than 50% of the tumor cells were accepted in accordance with WHO (2003) standards of NCB. Sensitivity and specificity for TMA sections vs whole‐mount sections were found to be 100% and 97.8%, respectively, suggesting that TMA analysis is a reliable method for NCB detection.