Problem: The proliferation of stromal cells in endometriosis promotes extensive adhesion; therefore, the morphological analysis of stromal lesions is important in the investigation of the pathogenesis of endometriosis.
Method of Study: In this study, the morphological and numeric comparisons of degranulated mast cells were performed between endometriotic lesions and comparative regions (eutopic endometrium and normal uterine serosa) of patients with and without endometriosis.
Results: In cases of endometriosis, diffuse infiltration of numerous mast cells was observed throughout the stromal lesions. These mast cells exhibited degranulation, and scattered granules were also observed. In the eutopic endometrium and normal uterine serosa of both the endometriosis patients and the controls, mast cells were rarely detected.
Conclusions: These results suggest that an abnormal immune response, specifically a hypersensitivity reaction, is strongly related to endometriosis; our findings will be helpful in the development of methods for the treatment of endometriosis.