most cases of choriocarcinoma occur in the uterine body and arise from chorionic villi following a normal or abnormal gestation . endometrioid adenocarcinoma of the uterine corpus with another histological type is usually squamous cell carcinoma , serous or clear cell adenocarcinoma and sarcoma , and there have been a few reports of choriocarcinoma 1 - 3 . we report a patient who had mixed cancer with three distinct histological types : endometrioid adenocarcinoma with squamous differentiation , choriocarcinoma in the uterine body and a disseminated peritoneal nodule showing papillary serous adenocarcinoma . an 85-year old woman , gravida 5 , parity 2 with menopausal status for 27 years presented with postmenopausal bleeding . a physical examination revealed a bulky uterus with pyometra . a subsequent transvaginal ultrasound showed an endometrial mass , measuring approximately 1.8 cm in diameter . magnetic resonance imaging showed a mass in the uterine cavity with myometrial invasion , which is consistent with the ultrasound findings . using [ 18f]fluoro-2-deoxy - d - glucose ( 18f - fdg ) positron emission tomography ( pet ) / computed tomography ( ct ) , we observed a uterine tumor with increased uptake and intense uptake in the left paracolic region indicating peritoneal dissemination , without signs of distant metastases . serum hcg- subunit , ca19 - 9 and cea levels were elevated to 8.0 ng / ml ( normal , < 0.1 ng / ml ) , 127.6 u / ml ( normal , < 37 u / ml ) , and 8.1 u / ml ( normal , < 5 ng / ml ) , respectively . the tumor was diagnosed as serous or endometrioid adenocarcinoma . under the diagnosis of endometrial cancer , total abdominal hysterectomy , bilateral salpingo - oophorectomy and multiple biopsies on macroscopic examination of the uterine specimen , a huge ulceroinfiltrative necrotic mass was located on the posterior wall , and a hemorrhagic nodule was located in the serosa of the uterine fundus and internal cervical os ( figure 1 ) . approximately half of the tumor showed an endometrioid adenocarcinoma with squamous differentiation ( figure 2a , 2b ) . the hemorrhagic nodule showed a choriocarcinoma component with a two - cell pattern that had syncytiotrophoblast - like and cytotrophoblast - like elements ( figure 3a ) . immunohistochemical staining for hcg- subunit was positive , especially in the syncytiotrophoblast - like element ( figure 3b ) . the biopsy specimen derived from peritoneal dissemination of the sigmoid colon showed a serous papillary adenocarcinoma ( figure 4a ) . positive immunohistochemical nuclear staining of p53 was detected in three distinct histological types ( figure 2c , 2d , 3c and 4b ) . transvaginal ultrasound showed a 5.2  5.3 cm - sized cul - de - sac mass . five months after surgery , the cul - de - sac mass was enlarged to 14.4  8.0 cm and caused rectosigmoid colonic obstruction . the patient underwent diverting colostomy to relieve the obstruction . a surgical biopsy showed poorly differentiated carcinoma with mononuclear cells ( figure 5a ) without any primary pathological features , although immunohistochemical staining for hcg- subunitand p53 was positive in part of the mononuclear cells , suggested cytotrophoblastic differentiation ( figure 5b and 5c ) . the combination of choriocarcinoma and other histological types has been reported in association with some human cancers , predominantly with the female genital tract 1 - 3 and rarely with carcinomas of the esophagus 4 , bladder or renal pelvis 5 , 6 , stomach 7 , rectum 8 , lung 9 , and breast 10 . in gynecological cases , an endometrioid adenocarcinoma with a choriocarcinoma component is a rare event with a highly aggressive clinical course 2 , 3 . in our case , because no pre - existing endometrium and endometrial hyperplasia localized with squamous and choriocarcinoma lesion , we considered this case showed the primary tumor which had three components : endometrioid adenocarcinoma with squamous and choriocarcinomatous differentiation and papillary serous adenocarcinoma . interestingly , the recurring tumor was poorly differentiated carcinoma with mononuclear cells that were different from primary pathological features . for the mechanism of development of a mixed tumor including a component of a choriocarcinoma , three hypotheses have been postulated : 1 ) de - differentiation of epithelial cells into choriocarcinomas 1 , 7 , 11 ; 2 ) germ cells that fail to complete their migration to the gonads 11 ; and 3 ) multidirectional tumor differentiation from a common stem cell 1 . recently , a small population of endometrial epithelial stem / progenitor cells was identified in normal human endometrium 12 , 13 . several studies have found that the endometrioid adenocarcinoma cell line contains a subpopulation of tumor initiating cells with stem - like properties . it is likely that the bulk of cells within a tumor consist of stem / progenitor cells and more differentiated cells 3 , 14 , 15 . the primary tumor showed three distinct histological types and the recurring tumor was poorly differentiated carcinoma with mononuclear cells that were different from the primary pathological features . these alterations suggest that multidirectional tumor was probably derived from aberrant differentiation of the somatic epitherial cells of the endometrioid adenocarcinoma , or might occur from a common stem cell . however , further studies on the pathogenesis of mixed tumors are required to determine this issue .
a choriocarcinoma component with a malignant tumor is relatively rare . we present a case of an 85-year - old woman with mixed carcinoma , which was endometrioid adenocarcinoma with squamous differentiation , choriocarcinoma and a disseminated peritoneal nodule , which was papillary serous adenocarcinoma . 
 the patient received surgery and conservative treatment . 
 twenty weeks after surgery , a recurring tumor appeared at the douglas pouch . 
 histology showed that the recurring tumor was poorly differentiated carcinoma that was very different from the primary tumor . 
 this case represents an unusual uterine corpus cancer with high - grade transformation with serous and choriocarcinomatous differentiation . 
 this case also demonstrates the capacity of tumor cells to differentiate into divergent elements .