Generally regarded as probable precursor lesion for prostate carcinoma.
Divided into low grade (mild dyplasia) and high grade Prostatic Intraepithelial Neopplasia (HGPIN, severe dysplasia).
HGPIN is detected in 80-100% of prostate harboring carcinoma.
Like in prostate cancer, TMPRSS-ERG fusion is also detected but at a lower rate in HGPIN (19%) than prostate cancer (~50%).
Preexisting (non-invasive) ducts and acini, usually medium to large size, lined by crowded cells with abnormal cytologic features (image A).
Has 4 major architectural patterns: micropapillary (image B), cribriform, tufted (image C) or flat.
Nuclei often show stratification.
Has nuclear features similar to cancer.
Unlike cancer, contains basal cell layer either continuous or discontinuous (remember non cancerous glands always has basal cells).
Immunohistochemistry: like in cancer AMACR is overexpressed, but unlike cancer basal cell markers (HMWK and p63)+ (image D).
Median risk of cancer following diagnosis of high grade PIN is 21%.
Presence of multifocal (>3) or bilateral HGPIN or associated with ASAP has higher risk for subsequent cancer.
Current recommendation is to repeat biopsy if HGPIN is identified in needle biopsy without cancer.
DDX: intraductal carcinoma(intraductal spread by cancer) of the prostate, which also has basal cells, high-grade secretory cells, and similarly has both AMACR and basal cell markers positivity.
Unlike HGPIN, intraductal carcinoma has larger expansile glands and neoplastic cells span the entire lumen.