American Urological Association - Atypical Adenomatous Hyperplasia (AAH)
Atypical Adenomatous Hyperplasia (AAH)
- Also known as adenosis, is a nodular proliferation of closely spaced small benign atypical glands.
- Occurs mostly in the transition zone (TZ).
- Usually an incidental finding, seen in up to 19% of TURP, <1% of needle biopsy and 33% of radical prostatectomy.
- A differential diagnosis for well-differentiated prostate carcinoma in biopsy.
- Lobular proliferation of small glands with minimal infiltration into the surrounding stroma (glands architecture overlap with cancer) (image A) & (image B).
- Abundant cytoplasm, pale to clear.
- Occasionally, crystalloids, amorphous eosinophilic secretions or mucin can be seen intraluminally (usually you see these features in cancer!).
- Immunohistochemistry: discontinuous staining for basal cell markers HMWK and p63 (cancer in contrast has complete absence of basal cells).
- Experts suggest that majority of the original Gleason grade 1 which is rarely diagnosed these days were Atypical Adenomatous Hyperplasia (AAH) (no immunohistochemistry yet at that time to look for basal cells).
- Weak evidence to suggest that AAH may represent a preneoplastic process, particularly for low-grade prostate carcinoma in TZ.