Standardizing the histopathological diagnosis of adenomyosis: an international Delphi consensus

Aims To use the Delphi consensus methodology to establish standardized criteria for the histopathological diagnosis of adenomyosis. Methods and results Between April and September 2024, a modified three‐round Delphi consensus study was conducted. Thirty‐one gynaecological pathologists from 18 countries participated in surveys to evaluate and refine a diagnostic framework for adenomyosis in hysterectomy specimens. Key areas achieving the highest level of agreement included: 4–6 blocks for routine histopathological examination of hysterectomy specimens with benign indications; defining adenomyosis as endometrial glands and/or stroma greater than 2 mm into the myometrium or more than one‐third of myometrial thickness; that the absolute number of glands or stromal tissue does not contribute to the diagnosis of adenomyosis; a single gland or stromal focus can be diagnostic; and definitions of focal, extensive, superficial and deep adenomyosis. In total, 93% of respondents were in favour of standardizing the diagnosis to reduce inter‐pathologist variability. Conclusion This study proposes the first consensus‐based guideline for the histopathological diagnosis of adenomyosis. Supported by the responses of 31 international experts through a modified Delphi method, this framework provides pathologists with clear diagnostic criteria. Further research should correlate these criteria with clinical symptoms and outcomes.