Which of the following is the MOST common histological variant of prostate cancer?

Prostate cancers are adenocarcinomas that arise from the prostatic acinar cells. In eighty-five percent of the cases, the adenocarcinoma is multifocal. Prostate cancers are graded according to their dysplasia, utilizing the Gleason scoring system. Sarcoma of the prostate accounts for 0.1% of all malignant prostatic tumors. Rhabdomyosarcoma is the most frequent mesenchymal tumor within the prostate, and is seen almost exclusively in childhood. Seminomas are not seen within the prostate. Seminoma is a germ cell tumor of the testis. Primary squamous carcinoma of the prostate is rare and is associated with a poor survival. More commonly, squamous differentiation occurs in the primary and metastatic deposits of adenocarcinomas after estrogen therapy. Also Know: Over 75% of cancers occur in the outer pa of the gland--mainly in the posterior pa. The most widely used and the one that correlates best with survival is Gleason's system, which uses two numbers representing the two predominant patterns in the tumor. The best- and worst-differentiated patterns, according to this system, are 1,1 (pure grade 1 lesions) and 5,5 (pure grade 5 lesions), respectively; a grade 2,4 carcinoma would show a mixture of moderately and poorly differentiated areas. Ref: Chandrasoma P., Taylor C.R. (1998). Chapter 51. The Testis, Prostate, & Penis. In P. Chandrasoma, C.R. Taylor (Eds), Concise Pathology, 3e.