Gastrointestinal tract endometriosis: Clinicopathologic features and anatomic distribution in an institutional cohort.

Endometriosis is defined by the presence of endometrial glands and stroma outside the uterine cavity. Although it typically presents within the pelvis, extragenital manifestations are well documented with gastrointestinal (GI) involvement being the most frequently affected organ system. We performed a retrospective study of histologically confirmed cases of endometriosis diagnosed at a single healthcare system between 2017 and 2024 to characterize the clinicopathologic features, anatomic distribution, and frequency within our institutional pathology cohort of GI tract involvement. A total of 1964 cases of endometriosis were identified, of which 150 (7.7%) demonstrated GI tract involvement, which comprised our main cohort. The majority of patients had no documented prior history of endometriosis (97%). CT/MRI was the most common modality used for diagnosis with 51%. Non-specific abdominal or pelvic pain (53%) followed by uterine bleeding (23%) were the most common presenting symptoms. GI-specific symptoms were found in only 17% of cases. Appendix was the most frequently involved site (77 cases) followed by rectum (45 cases), and sigmoid colon (40 cases). Involvement of a single isolated organ was seen in 56% of cases, with multi-site disease found in 44% of patients, and concurrent gynecological organ involvement found in 39% of cases. In 88% of cases, regular hematoxylin and eosin was used to render the diagnosis without the use of immunohistochemistry (IHC). The heterogeneity in both clinical presentation and pathologic findings for gastrointestinal endometriosis highlights the diagnostic complexity, and emphasizes the need for increased awareness to avoid histologic misinterpretation and facilitate timely recognition and management of patients.