the 
 occurrence   of primary sex cord - stromal tumors at extraovarian sites is 
 extremely rare . these tumors are predominantly granulosa cell tumors . 
 to our knowledge , this is the first case of primary mesenteric sertoli - leydig 
 cell tumor . a new case   of a 
 78-year - old   woman who 
 presented with bowel 
 obstruction is reported . three years previously , she underwent bilateral salpingo - oophorectomy and total 
 abdominal hysterectomy for bilateral mucinous cystadenoma and vaginal prolapse . ultrasonography showed a solid mesenteric tumor ; exploratory laparotomy showed 
 a nodular solid tumor at the mesenteric border of the distal ileum , measuring 
 11  8   cm . macroscopically , the tumor was nodular and well circumscribed measuring 11  8    4 cm . the cut surface was composed of pale yellow - grey soft tissue with foci of haemorrhage . microscopic examination revealed cellular lobules with nests and poorly 
 developed tubules of sertoli cells ( figure 1 ) that showed moderate atypia and 
 mitotic figures that average 510 per high - power field ( figure 2 ) . leydig cells are found at the periphery of the cellular 
 lobules ( figure 3 ) . by immunohistochemistry , the neoplastic cells showed 
 positive staining for antibodies against inhibin ( figure 4 ) and vimentin . tumor 
 cells were negative for ema ( epithelial membrane antigen ) , calretinin , 
 synaptophysin , chromogranin a , and cd117 ( c - kit ) . the diagnosis of 
 sertoli - leydig cell tumor with intermediate differentiation of the mesentery was 
 established . the patient has not received any additional therapy , yet she 
 remains free of disease after five years . the occurrence 
 of primary sex cord - stromal tumor at extraovarian sites is extremely rare , 
 such that in the english literature only 13 cases have been reported [ 113 ] . eight were classified as granulosa cell tumors [ 16 , 11 , 12 ] , two as thecomas 
 [ 7 , 8 ] , two as sex cord - stromal tumors , and one as an unclassified form of 
 stromal sex cord tumor . the sites of origin were usually within the pelvis 
 : six arose in the broad ligament , two in the retroperitoneum [ 2 , 12 , 13 ] , 
 one in the fallopian tube , one in an umbilical herniae sac , one in the 
 adrenal gland , and one in the pelvic sidewall . these previous reported 
 cases are summarized in table 1 . to our 
 knowledge , this is the first case of a primary mesenteric sertoli - leydig cell 
 tumor . however , in 
 our case , no biologic assay for estrogen content of the patient 's urine or 
 blood was performed , because the nature of the tumor was not suspected until it 
 was removed . the histogenesis 
 of extraovarian sex cord - stromal tumors has been reviewed in the literature . in recent 
 years , several investigators have claimed that the sex cords may originate from 
 the mesonephros . a dualistic theory of both coelomic epithelium and mesonephros 
 in the origin of the pregranulosa cells has also been proposed . accordingly , the mesonephros itself or its functional influence seems to be 
 necessary for creating the sex cords . this is consistent with gonad formation 
 being limited to the gonadal ridge and may explain why the sites of origin of 
 extraovarian sex cord - stromal tumors are limited to the broad ligament , 
 retroperitoneum , mesentery , and adrenal gland , all of which differentiate close 
 to the mesonephros and mesonephric duct . sex cord - stromal tumors can be 
 difficult to distinguish from several other neoplasms including 
 undifferentiated carcinoma , gastrointestinal stromal tumors ( gist ) or 
 metastatic melanoma . the prognosis 
 for extraovarian sex cord - stromal tumors seems to be favorable ; however , reported 
 cases and clinical experiences are limited .