Diagnostic criteria for ADH.
Low power view of a core biopsy specimen with small focus of ADH (left), contrasted with other TDLUs (center, right, and below).
Here we see a background columnar cell lesion with complex architecture; the atypical cells are starting to proliferate and make bars and arches.
Monotonous, non-overlapping cells filling an entire ductal lumen. Note the punched out, cookie-cutter like lumens.
Atypical ductal hyperlasia extends into lobules.
Note the micropapillary architecture. Calcifications are also found.
As described above and below, the lesion is less than 2mm.
Epithelial proliferations in the female breast can happen in two places - the terminal duct lobular unit (TDLU) and the ducts. When cells become neoplastic or clonal in the case of ductal carcinoma in situ, the neoplastic clone travels throughout a duct and all of its contiguous branches, including TDLUs.
There are several different scenarios that can result in a ADH diagnosis:
1. An epithelial proliferation in TDLUs in which the histologic features are identical to that of low grade DCIS, however, the proliferation does not involve true duct spaces or is less than 2 mm in greatest dimension (Humphrey).
2. Complex architecture in columnar cell lesions with atypia (aka 'flat epithelial atypia'). When the atypical cells begin to proliferate and make bars or arches (see images above), the proliferation fits the criteria for ADH.
3. Micropapillary lesions. An epithelial proliferation in a duct which meets architectural and cytologic criteria for micropapillary DCIS but only involves a minor portion of the circumference of the duct.
4. An atypical epithelial proliferation in TDLUs which does not meet histologic criteria for DCIS. This often includes lobular units expanded with a solid poliferation of cells which make rigid bars and/or rosettes but the cells still overlap somewhat.
If ADH is diagnosed on core biopsy, it is typically regarded as an indication for excision, given the high rate of DCIS. Some women who have ADH along with other breast cancer risk factors can be considered for treatment with tamoxifen to help reduce the chance of developing cancer.
In general, this diagnosis is associated with an increased risk of developing breast cancer 4 to 5 times the average lifetime risk.