PTEN Expression in Mucinous Prostatic Adenocarcinoma, Prostatic Adenocarcinoma With Mucinous Features, and Adjacent Conventional Prostatic Adenocarcinoma: A Multi-institutional Study of 92 Cases

Recent studies have demonstrated that most patients with mucinous prostatic adenocarcinoma may have a better prognosis than those with conventional prostatic adenocarcinoma; however, the mechanism remains unclear. Loss of phosphatase and tensin homolog (PTEN) expression is known to occur in aggressive high-grade prostatic adenocarcinoma, but expression in mucinous prostatic adenocarcinoma has not been well characterized. In this study, we sought to analyze PTEN expression in mucinous prostatic adenocarcinoma, prostatic adenocarcinoma with mucinous features, and the adjacent conventional prostatic adenocarcinoma. Cases were obtained from the Urologic Pathology files of 3 major academic institutions. Ninety-two cases were identified. PTEN expression was positive in the mucinous component of 79/92 (86%) cases. Concordant positive expression of PTEN between mucinous prostatic adenocarcinoma, prostatic adenocarcinoma with mucinous features, and the adjacent conventional prostatic adenocarcinoma was present in 60/79 (76%) cases. The fact that 86% of cases of mucinous prostatic adenocarcinoma and prostatic adenocarcinoma with mucinous features were positive for PTEN despite relatively high Gleason scores is in keeping with the fact that these tumors may be less aggressive than conventional prostatic adenocarcinoma without associated extraluminal mucinous components. In 76% of cases, the expression profiles (PTEN positive or negative) of mucinous prostatic adenocarcinoma and prostatic adenocarcinoma with mucinous features were similar to those of the adjacent conventional prostatic adenocarcinoma, implying that they may likely be clonal from a molecular standpoint. In addition, it is highly conceivable that the subset of PTEN-negative mucinous tumors may still have a relatively good prognosis due to a different/PTEN-independent protective pathway or mechanism.