Expression data from Neuroendocrine Prostate Cancer and Primary Small Cell Prostatic Carcinoma

Neuroendocrine prostate cancer (NEPC) is rare historically but may be increasingin prevalence as patients potentially develop resistance to contemporary anti-androgen treatment through a neuroendocrine phenotype. Diagnosis can be straightforward when classic morphological features are accompanied by a prototypical immunohistochemistry profile, however there is increasing recognition of disease heterogeneity and hybrid phenotypes. In the primary setting, small cell prostatic carcinoma (SCPC) is frequently admixed with adenocarcinomas that may be clonally related, while a small fraction of SCPC’s express markers typical of prostatic adenocarcinoma. Gene expression patterns may eventually help elucidate the biology underlying equivocal cases with discordant IHC, however studies to date have focused on prototypical cases and been based on few patients due to disease rarity. Here we examine 16 primary SCPC’s and 16 primary high grade adenocarcinomas profiled on exon arrays from archived formalin-fixed paraffin-embedded (FFPE)material. A total of 33 FFPE samples diagnosed as 16 small cell carcinomas, 16 high-grade adenocarcinomas (majority Gleason 9), and 1 adenocarcinoma with neuroendocrine differentiation were retrieved from surgical pathology and consultation files of Johns Hopkins Hospital from 1999-2013 and successfully processed for gene expression profiling withHuman Exon 1.0 ST GeneChips (Affymetrix). Samples came from 28 patients: on pathologic classification, 6 had evidence of SCPC alone, 10 had adenocarcinoma alone, 1 had adenocarcinoma with NE differentiation, and 11 had mixed histology tumors containing separate adenocarcinoma and SCPC components, with 4 matched pairs.