Re-evaluating the relevance of extensive intraductal component (EIC) in modern breast cancer management.

The concept of extensive intraductal component (EIC), currently defined by the presence of a prominent ductal carcinoma in situ (DCIS) component within an invasive tumor and extending beyond its margins, was introduced in the 1980s as a predictor of local recurrence following breast-conserving therapy for invasive breast carcinoma. At the time, surgical excision to negative margins was not the standard of care, making EIC a valuable tool for identifying patients at risk of recurrence. However, with modern oncologic and surgical advancements, its clinical relevance has diminished. Despite its continued inclusion as a mandatory entry in the CAP synoptic checklist, studies have shown that EIC does not independently predict local recurrence when margins are negative. Instead, objective parameters such as DCIS size and nuclear grade more accurately correlate with margin status and recurrence risk. While EIC may still be useful in preoperative biopsy assessments for evaluating disease extent among other things, its routine reporting in resection specimens appears less informative. Given its vague definition and limited prognostic value, we propose that EIC reporting should be discretionary rather than mandatory, with emphasis placed on more objective and clinically relevant metrics.