observedincombinationwithendometriosis.Theoretically, any histological type of tumor found in the endometrium might also occur in Endometriosis. Most of the malignant tumorsthatoriginatefromendometriosisareendometrioid adenocarcinoma and clear-cell types. On the other hand, sarcomas, especially endometrial stromal sarcoma (ESS), are extremely unusual (5). Malignant tumors arising from endometriosis can have their origins from the uterine wall as well as extrauterine. Heaps et al (4) reported a total of 205 malignant tumors arising from foci of gonadal and extragonadal endometriosis. The author reported that the mostfrequentlyinvolvedsitewastheovary(78.7%),andextragonadal tumors were present in 21.3% of all cases. The rectovaginalseptum(4.3%),colon(4.3%),vagina(2%),and pelvicperitoneum(5.7%)representedmostoftheextragonadal sites. Histologically, endometrial adenocarcinoma is the most common malignancy (about 70%), and sarcoma, includingmixedmesodermaltumors,was12%(4,6).Heaps et al do not clearly describe the exact incidence of ESS. In fact, mesenchymal tumors, such as ESS, are extremely uncommon,especiallyarisingfromendometriosisinvolvingthe intestinaltract(7). Severaldifferenttheoriesofpathogenesisofmalignant transformation in endometriosis have been discussed up to now. It is estimated that malignancy occurs in 0.7%-1% of all patients with endometriosis. Although the existence