Intramyometrial uterine cysts with special reference to ultrastructural findings: report of two cases.

An intramyometrial cyst is an extremely rare condition that is characterized by a benign, endometrial, epithelium-lined cyst within the thickened myometrium. Few cases of intramyometrial cysts have currently been reported in the literature, with or without microscopic description. We have experienced two cases of intramyometrial cysts. One was a 6.5 cm-sized cyst and the other was a 3.0 cm-sized cyst accompanied by adenomyosis. Case 1 was a 41-year-old female and case 2 was a 51-year-old female who had been suffering from menorrhagia for several days. A total hysterectomy was performed for both women. Histological examination showed that the huge cysts were composed of single-layered, ciliated, cuboidal epithelia surrounded by diffusely thickened myometrium. Ultrastructural examination of case 1 showed the lining cells of the cyst consisted of the basalis-type endometrial epithelial cells that have surface microvilli. The cells were surrounded by a duplicated basal lamina and joined by well-formed desmosomes. We report here on two cases of intramyometrial cyst with special reference to the ultrastructural examination, and we discuss the pathogenesis of this rare lesion.