[276] A Detailed Histologic Analysis of Flat Epithelial Atypia Diagnosed on Core Biopsy

Brian J Sutton, Kalliopi P Siziopikou, Megan E Sullivan. Northwestern University, Chicago, IL

Background: Flat epithelial atypia (FEA) remains a somewhat controversial diagnosis within breast pathology. The WHO established a definition in 2003, but interpretations and diagnostic thresholds vary between pathologists, and the features described in the literature are numerous and often subjective. In this study, we reviewed breast needle core biopsies (NCB) with FEA as the most significant diagnosis and scored each NCB for 15 different histologic features to determine if 1) different patterns of histologic features become evident and if 2) any specific pattern is more associated with upgrade at excision.
Design: After IRB approval, the pathology database was reviewed for NCB diagnosed as FEA between 1/1/03 and 12/31/10. Patients with atypical ductal hyperplasia (ADH) or cancer were excluded. 85 NCB were reviewed by MS & BS blinded to the excision findings and scored on the following features: dilation of TDLU, intralobular stroma, secretions, calcifications, basophilia, nuclear shape, size & distribution, nucleoli, cytoplasm, mitoses, myoepithelial cell prominence and presence of lobular neoplasia (LN). Relevant patient and excision data was also obtained.
Results: Using Ward's Method, the FEA NCB separated into 3 clusters. Nine histologic criteria were statistically significant in separating the clusters (p<0.0001, see table).

FeatureCluster 1 (N=34)Cluster 2 (N=16)Cluster 3 (N=35)
 “Intermediate”“Classic FEA”“HP-like”
Microcyst-like dilation16%79%5%
Expanded interlobular stroma76%1%60%
Overlapping nuclei4%2%19%
Loss of nuclear polarity9%19%0%
Eosinophilic cytoplasm26%14%0%
Prominent apical snouts14%24%6%
Prominent myoepithelial cells1%0%13%

The remaining histologic features showed no significant difference between the clusters. LN was twice as common in clusters 1 and 2. Excision pathology was available for 67/85. Two patients were upgraded to grade 1 DCIS, both from cluster 2 (2/16 or 12.5%). No patients from clusters 1 or 3 had cancer in their excision. ADH was present in excisions from each cluster with 12%, 6.7 % and 3.7% upgrade rates for clusters 1-3, respectively.
Conclusions: The term FEA is used to encompass NCB findings with subtle but seemingly distinct morphologies. The “classic FEA” NCB with microcyst-like dilation of the TDLU, loss of nuclear polarity, nucleoli and cytoplasmic snouts, without expanded intralobular stroma, carried the highest risk of upgrade to cancer at excision (12.5%). FEA NCB with more hyperplastic features were less associated with LN and only had a 3.7% upgrade rate to ADH on excision.
Category: Breast

Monday, March 19, 2012 8:15 AM

Platform Session: Section B, Monday Morning


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