Two cases of uterine adenocarcinoma which grew mainly in myometrium and showed unique histologic appearances are reported. Both cases were considered to have arisen from adenomyosis uteri because transitional figures were observed between carcinoma cells and adenmyotic glands in one case, and carcinomatous glands were scattered in myometrium and were associated with endometrial stroma which mimicked benign adenomyosis in another. The former case was poorly differentiated adenocarcinoma and the latter was well-differentiated adenocarcinoma. Interestingly, in the latter case, the carcinoma cells were transformed into papillary adenocarcinoma such as has been observed in the thyroid gland, and formed well-demarcated nodular mass. These findings indicate that adenocarcinoma which arise from adenomyosis uteri could show various histologic appearances, in addition to usual endometrioid adenocarcinoma.