Theca lutein ovarian cyst may be pathognomonic for trophoblastic neoplasia.

Two cases are presented in which theca lutein tissue was found at the time of indicated pelvic surgery performed long after treatment for hydatidiform mole. This indicator for the presence of trophoblastic tissue was not recognized, and clinical metastatic gestational trophoblastic neoplasia subsequently developed in each patient. Theca lutein tissue found at pelvic surgery merits investigation by beta-human chorionic gonadotropin radioimmunoassay and is likely to be associated with subclinical latent trophoblastic neoplasia.