OBJECTIVETo study the clinicopathologic features of 30 cases of pseudohyperplastic prostatic adenocarcinoma (PHPA).

METHODSEight hundred and sixty cases of ultrasound-guided prostatic needle biopsy and 46 cases of radical prostatectomy specimens collected during the period from January 1, 2005 to December 31, 2006 were retrieved from the archival files. The incidence, morphology, pathologic differential diagnosis, tumor volume, preferred location and Gleason's score were studied. The tissue sections suspicious for PHPA were immunohistochemically stained with high-molecular weight cytokeratin (34betaE12) or CK5/6, p63, AMACR, and cocktail antibody of 34betaE12/p63/AMACR. Cases with PHPA component more than 60% in at least one single slide were selected and pathologically analyzed.

RESULTSPHPA was present in 7% of needle biopsy and 15.2% of prostatectomy specimens. Histologically, 66.7% of PHPA demonstrated direct transition with conventional acinar adenocarcinoma; and 76.7% of cases had coexisting conventional acinar adenocarcinoma in the remaining tissue blocks. The tumor volume accounted for 5% to 100% of total carcinoma among core needle biopsy and 1% to 30% of total carcinoma among radical prostatectomy. PHPA resembled benign prostate glands, in which the hyperplastic malignant acini were predominantly of medium to large size. The neoplastic cells were well-differentiated, with basally located nuclei and luminal corpora amylacea. However, amongst the 20 pathologic indices of prostatic malignancy studied, occurrence of 10 or more indices exceeded 66.7%. Although PHPA looked benign morphologically, 66.7% cases had stromal invasion, 6.7% had perineural invasion and 3.3% had bone metastasis. The tumor was primarily located in the peripheral zone.

CONCLUSIONSPHPA is not a rare phenomenon in prostatic adenocarcinoma. Majority of cases have concurrent conventional acinar adenocarcinoma. It is different from well-differentiated (with Gleason's score 1 or 2) adenocarcinoma with a relatively indolent clinical course. In contrast, PHPA corresponds to moderately differentiated adenocarcinoma with Gleason's score of 3.