Overlap of CD44 expression between prostatic small cell carcinoma and acinar adenocarcinoma

Small cell carcinoma (SmCC) of the prostate is a rare and aggressive histologic subtype of the prostate cancer. It can sometimes mimic acinar adenocarcinoma with a high Gleason score (GS). A previous study showed that immunohistochemical staining for CD44 could help in the differential diagnosis of these 2 entities. In this study, we used 2 tissue microarrays including 63 cases of prostate cancer (18 pure SmCC, 37 pure acinar adenocarcinoma, and 8 mixed acinar adenocarcinoma and SmCC) to validate the value of CD44. When analyzed as a continuous variable, CD44 positivity was significantly higher in acinar adenocarcinoma with GS 8 than GS 9 to 10 (P = .027). However, the difference of CD44 expression between SmCC and acinar adenocarcinoma was insignificant. The current study fails to confirm the value of CD44 in differential diagnosis between prostatic SmCC and acinar adenocarcinoma.