gestational trophoblastic neoplasia ( gtn ) comprises a spectrum of malignant tumors derived from the trophoblast including the invasive mole ( i m ) , the choriocarcinoma ( ch ) , the placental site trophoblastic tumor ( pstt ) and the epithelioid trophoblastic tumor ( ett ) . pstt is a rare entity with less than 300 cases reported and accounts for 12% of gtn . however , a wide range of other presenting symptoms has been reported such as abdominal pain , uterine rupture and galactorrhea ( gillespie and hancock , 2009 ) . this slow - growing tumor tends to stay initially in the uterus but more than 30% of patients have metastatic disease at the time of presentation ( schmid et al . , 2009 ) . the sites of metastases include the peritoneum , the lung , the liver and the brain . pstt may follow any gestational event , normal or pathological pregnancy . in a series of 55 cases ( baergen et al . , 2006 ) , the diagnosis was made within an interval of 34  months following a previous gestation , mainly affecting women of childbearing age . the prognosis of pstt depends on the disease 's extent ( schmid et al . , 2009 ; baergen et al . , 2006 ; partial myometrectomy may be performed to preserve fertility ( saso et al . , 2012 ) . the prognosis drops rapidly when metastatic disease is present . for advanced - stage diseases , a combination of surgery and polychemotherapy we report the case of a patient who develops a recurrence of an ignored pstt at the vaginal vault diagnosed 8  years after her last pregnancy and 4  years after a hysterectomy for benign condition . a 46-year - old woman , gravida 4 , para 3 , presented to her gynecologist complaining of abdominal pain and purulent vaginal discharge . the last one was 8  years prior to her presentation and a tubal ligation was performed . four years later , she underwent a total hysterectomy for recurrent and infected hematocolpos in semi - urgent clinical conditions with no further histological or radiological preoperative work - up . histological report showed an incomplete healing of the uterine cesarean scar and a high - grade cervical intraepithelial neoplasia . clinical and ultrasound examination revealed an ovarian mass consistent with an adnexal abscess of the left ovary and an indurated vaginal vault . the infectious episode resolved promptly but the vaginal biopsy revealed an unexpected vaginal invasive squamous cell carcinoma . clinical examination , pelvic mri and pet - ct identified suspicious bilateral multilocular ovarian cysts and a 2  cm mass limited to the vaginal vault without parametrial extension . the patient underwent resection of the vaginal lesion , bilateral salpingo - oophorectomy and pelvic lymphadenectomy . the macroscopic examination of the vaginal tumor reveals an ill - defined nodular growth measuring 3.5    3.5    3.8  cm . the mass is pearly white color with areas of hemorrhage ( fig .  1 , a ) . on microscopic examination , the tumor consists of a pleomorphic population of polygonal intermediate trophoblast cells with amphophilic to clear cytoplasm . these cells have often a single irregular highly atypical nucleus with focally prominent nucleoli , but some are multinucleate , resembling to syncytiotrophoblastic giant cells ( fig .  1 , b&c ) . mitotic figures ( 2/10 high power field ) , extensive necrosis , hemorrhage and vascular invasion are observed . the staining of hcg , hpl and inhibine is only focally positive while the staining of placental alkaline phosphatase ( plap ) is more diffuse . the staining of ckae1/ae3 and ck7 is positive and the staining of ck5/6 and p63 is negative . the pathological diagnosis of pstt is proposed and confirmed by the expert panel of pathologists of the belgian referent center of gtd . , the pathology slides of the hysterectomy performed 4  years previously were reviewed and showed no sign of pstt . the serum hcg concentration was elevated to 41.0 ui / l the day after the surgery . considering that surgery remains the preferred treatment for patients with localized pstt , that total surgical resection of the unique lesion was achieved and that pstt tends to be resistant to chemotherapy , observation has been elected . after a follow - up of 10  months , the patient is still in clinical , biological ( -hcg ) and radiological ( pelvic mri ) remission . as shown in this case report , clinical and pathological presentation of pstt can be extremely variable . it can be challenging to distinguish pstt from other forms of gtn or nontrophoblastic tumors . the review of the pathology by experts in this field is of paramount importance as demonstrated by the experience from several european referral centers . in contrast to other forms of gtn , pstt arises from the implantation - site intermediate trophoblast . given that hcg is produced by syncytiotrophoblasts , the serum hcg levels in pstt do not correlate with the tumor burden neither with the malignant behavior and thus have no predictive value ( hassadia et al . , 2005 ) . furthermore , the hcg - free  - subunit is the main form of hcg in pstt , as reported recently by cole et al . , and could be used to distinguish pstt from other trophoblastic neoplasia and nontrophoblastic tumors that produce hcg ( cole et al . , 2006 ) . the classical immunophenotypic pattern of pstt in comparison of choriocarcinoma and nontrophoblastic tumor is illustrated in table  1 ( mazur , 2005 ) . however , as observed in the present case , there is some overlapping between diagnostic criteria for pstt and choriocarcinoma . information about optimal management strategy is restricted because the condition is rare and the natural course varies widely . the revised 2000 figo staging system ( oncology , 2002 ) has a prognostic and therapeutic usefulness for gtn . indeed , studies show that prognostic factors of the gtn staging system do not apply accurately to pstt . the figo anatomical staging system is the strongest predictor of patient outcome presenting with pstt ( schmid et al . , 2009 ; baergen et al . , a retrospective review of 62 patients with pstt treated over a 30-year period indicates that the probability of 10-year overall survival for those with stage i , ii or iii / iv disease was respectively 90 , 52 and 49% . this further supports the importance of an early diagnosis ( schmid et al . , 2009 ) . other factors associated with an unfavorable outcome include patient 's age ( older than 35  years ) , prolonged intervals from previous pregnancy ( over 48  months ) , prior term pregnancy , high hcg level ( over 1000  miu / ml ) , tumor size , depth of myometrial invasion , tumor necrosis , high mitotic count ( over 5 per 10 hpf ) and clear cytoplasm . it is interesting to note that the prognostic factors are derived from pathological analysis of the uterus and therefore are not fully applicable for the present case . ( 2009 ) report that the prognosis of patients developing recurrent or refractory disease is poor and that only four ( 22% ) patients achieved long - term survival beyond 60  months . to our knowledge , they recommend adjuvant chemotherapy for patients who have risk factors of recurrence or persistent raised postoperative serum hcg level or both . patients with stage ii , iii or iv pstt are usually managed with combined surgery and chemotherapy . there is no definitive evidence of benefit of adjuvant chemotherapy for stage ii disease . given that pstt is less chemotherapy responsive than other types of gtn , polychemotherapy is recommended . although there is no conclusive difference between platinum - based versus non - platinum based regimens , a platinum - containing multidrug chemotherapy is generally preferred such as ep / ema ( schmid et al . , 2009 ) . gynecologists confronted with vaginal lesion must consider besides primary vaginal tumors , secondary vaginal implants even if the patient underwent a hysterectomy . indeed , 84% of vaginal cancers are metastases and arise not only from gtn but also from other gynecologic malignancies , melanoma , hypernephroma , bladder cancer , breast cancer and colorectal adenocarcinoma . any gynecologist who has to deal with pstt faces a challenge not only in terms of diagnosis but also in terms of therapy . although several authors try to establish management strategy , a management algorithm remains controversial because of the lack of data due to the low incidence of the disease and its unpredictable course . patients should ideally be referred to a center with expertise in gestational trophoblastic disease to assure their optimal care . written informed consent was obtained from the patient for publication of this case report and accompanying images . a copy of the written consent is available for review by the editor - in - chief of this journal on request .