Molecular analysis has shown that high grade PIN and prostate cancer share many genetic abnormalities.

[3] HGPIN typically has one of four different histologic patterns:[2] Its cytologic features are that of prostatic adenocarcinoma: Microscopically, PIN is a collection of irregular, atypical epithelial cells.

They remain fully contained within a prostate acinus (the berry-shaped termination of a gland, where the secretion is produced) or duct.

The latter can be demonstrated with special staining techniques (immunohistochemistry for cytokeratins) to identify the basal cells forming the supporting layer of the acinus.

[7] Because it is thought to be a premalignant state, PIN is often considered the prostate equivalent of what is called carcinoma in situ (localized cancer) in other organs.

[3] HGPIN is diagnosed from tissue by a pathologist, which may come from:[citation needed] Blood tests for prostate specific antigen (PSA), digital rectal examination, ultrasound scanning of the prostate via the rectum, fine needle aspiration or medical imaging studies (such as magnetic resonance imaging) are not useful for diagnosing HGPIN.

[citation needed] On a subsequent biopsy, given a history of a HGPIN diagnosis, the chance of finding prostatic adenocarcinoma is approximately 30%.