Mucinous differentiation in the prostate ranges from mucinous metaplasia on the benign end of the spectrum all the way to mucinous (colloid) adenocarcinoma. The image shows extensive mucinous metaplasia in a nodule of benign prostatic hyperplasia in a transurethral resection specimen. Clusters of mucinous glands lined by tall columnar cells are seen admixed with usual prostatic glands. The mucin is positive for mucicarmine, PAS, and alcian blue. The glands are negative for PSA and PAP.