Incidence of Adjacent Synchronous Ipsilateral Infiltrating Carcinoma and/or Ductal Carcinoma In Situ in Patients Diagnosed with Flat Epithelial Atypia by Core Needle Biopsy (TBCRC 034).

Background: Flat epithelial atypia (FEA), a rare breast proliferative lesion, is often diagnosed following core biopsy (CB) of mammographic microcalcifications. In the prospective multi-institution TBCRC 034 trial, we investigate the upgrade rate to ductal carcinoma in situ (DCIS) or invasive cancer following excision for patients diagnosed with FEA on CB.

Patients And Methods: Patients with a breast imaging reporting and data system (BI-RADS) ≤ 4 imaging abnormality and a concordant CB diagnosis of FEA were identified for excision. Upgrade rates were determined on the basis of local and central pathology review. The prespecified threshold to omit excision of FEA on CB was an upgrade rate of ≤ 3%. Sample size and confidence intervals were based on exact binomial calculation.

Results: Overall, 129 patients underwent excision (median age 50 years, range 30-84 years). After local pathology review, 6/129 patients (4.7%; 95% CI 1.7-9.8%) were upgraded to invasive carcinoma (n = 3) or DCIS (n = 3) at excision. Among 116 patients with CB available for central pathology review, FEA was confirmed in 78 (67.2%, 95% CI 57.9-75.7%). Of these, only one patient was upgraded to DCIS (1.3%; 95% CI 0.03-6.9%), which was also one of the locally upgraded cases. Among the other five local upgrades, two did not have CB available for central review, two CB had ADH, and one CB had normal tissue on central review.

Conclusions: Among patients with FEA on CB, the upgrade rate was 4.7% based on local pathology review and 1.3% based on central pathology review. These findings highlight the importance of shared decision-making in the management of FEA.