Xanthogranulomatous endometritis associated with endometrial carcinoma.

We studied a case of xanthogranulomatous (XG) endometritis associated with endometrial adenocarcinoma. Isolated XG endometritis is a rare entity that may mimic carcinoma as a consequence of the replacement of the endometrium and the invasion of the myometrium by friable yellowish tissue composed of foamy histiocytes. To our knowledge, it has not previously been described as coexisting with a carcinoma. The XG reaction is characterized by pigment-laden foamy cells. Electron microscopy demonstrated that the foamy cells belong to the macrophage/histiocyte series and are not endometrial stromal cells. Histochemical studies revealed the pigment to be composed of hemosiderin and lipofuscin. The absence of calcispherites or a uniform immunoperoxidase staining reaction for alpha 1-antitrypsin excluded the diagnosis of malacoplakia. We have postulated that XG endometritis has a similar etiopathogenesis to XG pyelonephritis and XG cholecystitis. It is a rare morphologic expression of the clinical syndrome of benign senile pyometrium.