EVIDENCE FOR MONOCLONAL EXPANSION OF EPITHELIAL-CELLS IN OVARIAN ENDOMETRIAL CYSTS

Ovarian endometrial cysts, one of the typical manifestations of endome triosis, are generated by the retention of cyclic hemorrhages and are classified as tumor-like lesions rather than neoplasms. Clonality anal ysis provides important information about the histogenesis and progres sion of neoplastic diseases. As it is generally accepted that most neo plasms are monoclonal in origin, however, the clonality of endometrial cysts remains uncertain. Using the human androgen receptor gene (HUMA RA) as an X-linked polymorphic marker, we examined the clonal statics of epithelial cells in endometrial cysts. We separated 21 fresh epithe lial cell samples from 11 endometrial cysts and found that all were mo noclonal in the methylation pattern of the HUMARA alleles. Moreover, i n each of the five cysts front which epithelial cells were sampled fro m multiple and distant areas, the methylation patterns of all samples from a single cyst were identical. These data indicate that endometria l cysts are monoclonal in origin and suggest their neoplastic potentia lity.