American Urological Association - Prostatic Intraepithelial Neoplasia (PIN)
Prostatic Intraepithelial Neoplasia (PIN)
- 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.