Large-Needle Core Biopsy in Atypical Intraductal Epithelial Hyperplasia Including Immunohistochemical Expression of High Molecular Weight Cytokeratin: Analysis of Results of a Single Institution

The diagnosis of atypical intraductal epithelial hyperplasia (AIDH) constitutes 6.3% of the breast core biopsies performed at our institution. Seventy-nine cases that were diagnosed as AIDH on core biopsy and went through excisional biopsy were included. Sixty-four biopsies were performed by an image-guided 11-gauge vacuum device, 11 under sonographic guidance using 14-gauge needles and 4 by a sonographically guided 11-gauge vacuum device. The histopathology of the core biopsies and the surgical excisions were reviewed. Immunohistochemistry was performed on the consecutive sections of core biopsy specimens using high molecular weight cytokeratin (HMW-CK) (DAKO-Cytokeratin, 34βE12). At interpretation of the stain, intensity and percentage of positive cells were taken into account. The immunoprofiles of AIDH were categorized into four groups showing negative (i.e., no staining) or low-, moderate-, high-, and very high-intensity staining. Surgical excision of the 79 lesions revealed carcinoma in only 3 cases (4%)-two infiltrating carcinomas and one intraductal carcinoma—residual AIDH in 44 cases (56%), and epithelial hyperplasia or other benign lesions without atypia in 32 cases (40%). The HMW-CK stain was performed retrospectively on all of the core biopsies and 66 of them contained residual areas with AIDH for staining. Forty-nine (74%) were CK negative or stained with low intensity, but 17 cases (26%) had a moderate- to high-intensity stain. Our study showed a lower incidence of carcinoma on surgical excision following core biopsy for AIDH than other studies. The HMW-CK stain helped to characterize the nature of the intraductal proliferation and to confirm the presence of atypia, as has been previously reported, but frequently was inconclusive. The low incidence of carcinoma brings into question the need for surgical excision of all cases of AIDH diagnosed by core biopsy.