Background: Available retrospective data suggest the upgrade rate for intraductal papilloma (IP) without atypia on core biopsy (CB) ranges from 0 to 12%, leading to variation in recommendations. We conducted a prospective multi-institutional trial (TBCRC 034) to determine the upgrade rate to invasive cancer (IC) or ductal carcinoma in situ (DCIS) at excision for asymptomatic IP without atypia on CB. Methods: Prospectively identified patients with a CB diagnosis of IP who had consented to excision were included. Discordant cases, including BI-RADS > 4, and those with additional lesions requiring excision were excluded. The primary endpoint was upgrade to IC or DCIS by local pathology review with a predefined rule that an upgrade rate of ≤ 3% would not warrant routine excision. Sample size and confidence intervals were based on exact binomial calculations. Secondary endpoints included diagnostic concordance for IP between local and central pathology review and upgrade rates by central pathology review. Results: The trial included116 patients (median age 56 years, range 24–82) and the most common imaging abnormality was a mass (n = 91, 78%). Per local review, 2 (1.7%) cases were upgraded to DCIS. In both of these cases central pathology review did not confirm DCIS on excision. Additionally, central pathology review confirmed IP without atypia in core biopsies of 85/116 cases (73%), and both locally upgraded cases were among them. Conclusion: In this prospective study of 116 IPs without atypia on CB, the upgrade rate was 1.7% by local review, suggesting that routine excision is not indicated for IP without atypia on CB with concordant imaging findings.
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