Atypical Ductal Hyperplasia


  • ADH is a predictor of risk as well as a non-obligate precursor for breast cancer

  • Proliferative breast disease with some, but not all, features of LOW GRADE DCIS

  • Clonal proliferation of luminal-like cells, but lack sufficient features to be called DCIS

  • If you see high grade features, it makes it high grade DCIS

  • ADH is still confined to the ducts (maintains ME layer)

  • Clinical picture

  • Mammography shows suspicious dense area with microcalcifications

  • ADH diagnosis on a biopsy generally calls for a complete excision

  • EXCEPTION if the biopsy was for microCa++ (not a mass), there is only one 1 or 2 foci of clear-cut ADH present and post-biopsy mammogram reveals no residual Ca++ at all

  • Breast cancer risk

  • 4-5x increased risk of breast cancer (60% in ipsilateral breast)

  • Shows loss of 16q and 17p

  • Higher risk if there are multiple atypical foci present or if normal regression/involutional changes are decreased in background lobular units (breast is supposed to become more fat, less glandular as you get older...seeing a lot of glands still is a bad sign)

  • Histology

  • Cluster of weird ductular structures with some myoepithelial cells still appreciated

  • Lacks nuclear uniformity, even spacing and well defined round secondary lumens of low grade cribriform DCIS

  • Epithelial cells have atypia with variation in size & shape!!

  • Some are enlarged & slightly hyperchromatic

  • ADH does NOT fill the entire ductal space and lacks the monomorphism that is seen in DCIS or LCIS.


  • Typically shows strong diffuse positivity with ER stain (normal ducts & lobules have a subset of positive cells)

  • Express LMWCK (red cytoplasm), but not HMWCK (brown cytoplasmic staining in myoepithelial cells)

  • (UDH should show a heterogeneous staining pattern)

  • HMW keratin (CK903; aslo called 34bE12) and CK5/6 are generally NEGATIVE in ADH/LG DCIS

  • When to call ADH:

  • Basically, ADH looks worse than UDH, but not bad enough to call DCIS

  • We want the clinician to know there is some funky stuff going on in the breast, but there just isn’t quite enough to justify calling it DCIS.

  • Sometimes, the duct in question may even fit all of the criteria for calling it a low grade DCIS, but pathologists may call it ADH if:

  • There is only a single focus present

  • The size is < 2mm

  • <3 ducts are involved

  • Process that run along the ductal system and undermine or replace the normal epithelium of ducts/lobules favor ADH or DCIS

  • HMW keratin (CK903; aslo called 34bE12) and CK5/6 are generally NEGATIVE in ADH/LG DCIS


  • Keep in Mind:

  • There is a big difference in calling something usual ductal hyperplasia (no increased risk for breast cancer) vs. atypical ductal hyperplasia (inc risk for breast cancer).

  • You don’t have to worry as much about whether to call something ADH vs. DCIS- these both have an increased risk for cancer.

  • The clear presence of well defined ME layer is reassuring in calling something benign. However, the presence/absence of myoepithelial cells is not as valuable for intraductal processes since some intraductal carcinomas retain some degree of myoepithelial cells around the periphery; these ME cells are usually attenuated or partially lost in tumor cells.

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These posts contain high yield information collected from various educational resources including textbooks, journal articles, educational websites and more. They are intended for educational use only and should NOT be taken as medical advice. I strongly believe the spreading of knowledge and depth of learned information should be encouraged in today's society rather than coveted. Membership is required to view these posts  and should be used solely for educational purposes only.