Characteristics of histologically confirmed endometriosis in cynomolgus monkeys

STUDY QUESTION: What are the characteristics of spontaneous endometriosis in cynomolgus monkeys? SUMMARY ANSWER: Spontaneous endometriosis in cynomolgus monkeys exhibited similar characteristics to the human disease. WHAT IS KNOWN ALREADY: One previous report described the prevalence and the basic histopathology of spontaneous endometriosis in cynomolgus monkeys. STUDY DESIGN, SIZE, DURATION: Endometriotic lesions that had been histologically confirmed in 8 female cynomolgus monkeys between 5 and 21 years old were subjected to study. PARTICIPANTS/MATERIALS, SETTING, METHODS: The monkeys died of, or were sacrificed because of, sickness consequent on endometriosis. Specimens were evaluated histopathologically with haematoxylin and eosin staining, iron staining and immunohistochemistry (CD10, CD31, α-SMA and PGP9.5), and by observing them under a microscope. MAIN RESULTS AND THE ROLE OF CHANCE: Endometriotic and stromal cells (CD10-positive) with haemorrhage and inflammation were observed. Smooth muscle metaplasia and nerve fibres were also noted in the endometriotic lesions. Endometriotic lesions in lymph nodes were incidentally found. LIMITATIONS AND REASONS FOR CAUTION: Since laparoscopic analysis for monitoring the disease state was not set as a parameter of the current study, time course changes (progression) of the disease were not assessed. WIDER IMPLICATIONS OF THE FINDINGS: Further investigation of spontaneous endometriosis in cynomolgus monkeys may contribute to better understanding of the disease pathobiology. STUDY FUNDING/COMPETING INTEREST(S): No external funds were used for this study. A.N.K., S.M., S.H., T.I., O.K., A.K. and M.S. are full-time employees of Chugai Pharmaceutical Co., Ltd. R.K. received lecture fees from Chugai Pharmaceutical Co., Ltd., unrelated to the submitted work. S.N., S. O., L.Y., K.Y. and T.S. have nothing to declare. TRIAL REGISTRATION NUMBER: N/A.