We report two cases of the so-called adenomatoid tumor of the uterus, which have been detected in patients who underwent surgery for leiomyomas. The clinical signs, origin and immunohistochemical characteristics of the adenomatoid tumor are described. Adenomatoid tumors are slow growing epithelioid neoplasias with a co-expression of vimentin and cytokeratins. The characteristic cytokeratins are numbered 7, 8, 18, 19 and 5. The mesothelial histogenesis of the tumor can be confirmed. Our results rule out origins from Müllerian or mesonephrogenous ducts and angioma or adenoma. Considering our experiences, adenomatoid and leiomyoma cannot be distinguished macroscopically. The hysterectomy or salpingo-oophorectomy, primarily performed under other diagnoses, are the therapies of choice.