High-grade prostatic intraepithelial neoplasia (HGPIN) is an abnormality of prostatic glands and believed to precede the development of prostate adenocarcinoma (the most common form of prostate cancer). It may be referred to simply as prostatic intraepithelial neoplasia (PIN). It is considered to be a pre-malignancy, or carcinoma in situ, of the prostatic glands..