Immunohistochemical study was carried out in a case of adenomatoid tumor of the uterine corpus. The patient was a 35-year-old female. The tumor showed classical histochemical and immunohistochemical findings of mesothelioma, i.e., presence of hyaluronic acid on the cellular surface and cytokeratin in the cytoplasm. In addition, the tumor showed positive reaction to anti-vimentin. Furthermore, absence of Ber-Ep4 supports mesothelial origin of this tumor. EMA reaction was reported only in one case in the literature. The result was negative as in our case. Therefore, it was suggested that at least some of the adenomatoid tumor were negative for EMA as in malignant mesothelioma, although this tumor was benign. Therefore, it was suggested that loss of EMA in mesothelial tumor was not always related to anaplastic change.