tailgut cysts or retrorectal cystic hamartomas are rare congenital presacral lesions identified in all age groups . they are believed to arise from the remnants of the embryonic hindgut .
malignancy in tailgut cysts is extremely rare , the majority being adenocarcinomas and carcinoid tumors .
a unique feature of our case compared with previously reported tailgut cysts is that this patient 's blood irregular antibodies are positive with higher operational risks .
a 44-year - old woman presented to our department complaining of pelvic and perineal pain for 6 months .
a nontender , extrinsic , well - defined presacral mass was discovered by digital rectal examination which compressed the rectum .
computed tomography ( ct ) scan of the abdomen and pelvis demonstrated a well - demarcated hypodense , multilocular cystic lesion , 10  cm in size , in the presacral region of the right of the midline ( fig .
1 ) . we found her blood irregular antibodies were positive in the preoperative examination .
at exploratory laparotomy for excision of the lesion , we found that the mass was adherent to and not easily separated from the rectum and surrounding pelvic wall .
abdominal ct demonstrated that lesion was bigger than the last ct image , 14  cm in size ( fig .
2 ) . what 's more , the patient had difficulty in passing her motions with shape changing .
abdominal ct demonstrated that lesion was bigger than the last ct image , 16  cm in size ( fig .
3 ) . taking into account the cystic mass , paracentesis was carried out with about 2000  ml yellow liquid extracted .
we found that the mass was adherent to and not easily separated from the rectum and surrounding pelvic wall .
combined with clinical symptom and imaging , malignant transformation of retrorectal cystic hamartomas ( tailgut cysts ) was diagnosed ( fig .
4 ) . then tumor necrosis factor ( tnf ) and raltitrexed were infused into the cysts and 3 cycles oxaliplatin ( 130  mg / m ) were completed .
now although the lesion is shrinking , but yellow , viscous mucus still secrete constantly , 100  ml / w . as surgical excision
is the essential for treatment , we still suggest this patient to operate by prestoring herself blood and autologous blood transfusion .
the ct image took in february 2013 , 10  cm in size , in the presacral region to the right of the midline .
postoperative routine pathology : combined with clinical symptom and imaging , malignant transformation of retrorectal cystic hamartomas ( tailgut cysts ) was diagnosed .
this study was approved by the institutional review boards and ethics committees of shandong cancer hospital and institute .
in the literature , various terms have been used to describe tailgut cysts , including cyst of the postanal intestine , mucus - secreting cyst , retrorectal cystic hamartomas , simple cyst , retrorectal cyst , and enterogenous cyst .
it was most often found in asymptomatic middle - aged women . because the lesion is located in the bathy - pelvis and extremely rare , so it is difficult to diagnosis .
ultrasound shows multilocular cystic lesions with internal echoes due to mucoid material or inflammatory debris .
abdominal ct demonstrated a well - demarcated hypodense , bilocular cystic lesion in the presacral region .
there is one report of endoscopic ultrasonography - fine needle aspiration ( eus - fna ) with a flexible echoendoscope .
puncture should be performed when other etiologies are considered or if malignant degeneration changes management .
malignant transformation in the form of adenocarcinoma or neuroendocrine tumors , although rare , does occur .
mathis et al reported 31 patients with tailgut cysts and 4 of them ( 13% ) had malignant findings : adenocarcinoma in 3 and neuroendocrine tumors in 1 .
they concluded that presacral tailgut cysts should be removed because of the risk of malignant transformation , because 2 of the 4 patients with malignancy had died through the follow - up period .
therefore , complete resection of these lesions is recommended , as surgical excision is the gold - standard treatment .
the treatment of choice is complete excision of the lesion , with resection of the coccyx and a surrounding margin of grossly normal tissue .
if surgery can not be carried out , systemic chemotherapy and local radiotherapy can be implemented .
prognosis for tailgut cysts with malignant transformation depends on the status of complete surgical resection and tumor histology and grade .
two cases with local recurrences and 1 case with a distant metastasis have been reported in adenocarcinomas arising in tailgut cysts in the literature .
tailgut cysts should be taken into account , if a retrorectal mass can not be diagnosis clearly .
given surgical excision is the essential for treatment , complete surgical excision should be implemented as far as possible .
malignant transformation , although unusual , may be focal , so meticulous examination of the gross mass and thorough samplings are important . the coccyx and a surrounding margin of grossly normal tissue should also be excision , when malignant transformation was confirmed .
but if surgery can not be carried out like the presented case , systemic chemotherapy and local radiotherapy are also available , which can alleviate the symptoms of oppression and improve the quality of life partly .
 abstractretrorectal cystic hamartomas are rare congenital presacral lesions and malignancy is extremely rare . 
 although surgical excision is the essential for treatment , a unique feature of our case compared with previously reported tailgut cysts is that this patient 's blood irregular antibodies are positive with higher operational risks.a 44-year - old woman presented to our department complaining of pelvic and perineal pain for 6 months . 
 computed tomography ( ct ) scan of the abdomen and pelvis demonstrated a well - demarcated hypodense , multilocular cystic lesion , 10  cm in size , in the presacral region of the right of the midline . 
 we found her blood irregular antibodies were positive in the preoperative examination . 
 so she quitted surgery . 
 exploratory laparotomy and incision and drainage of pelvic tumor were operated . 
 postoperative routine pathology showed : ( retroperitoneal tumors ) moderately differentiated adenocarcinoma . 
 combined with clinical symptom and imaging , malignant transformation of retrorectal cystic hamartomas ( tailgut cysts ) was diagnosed . 
 taking into account that cyst is not sensitive to radiotherapy , so tumor necrosis factor ( tnf ) and raltitrexed were infused into the cysts and 3 cycles oxaliplatin ( 130  mg / m2 ) were completed . 
 now although the lesion is shrink , but yellow , viscous mucus still secrete constantly , 100  ml / w.given surgical excision is the essential for treatment , complete surgical excision should be implemented as far as possible . 
 but if surgery can not be carried out like the presented case , systemic chemotherapy and local radiotherapy are also available , which can alleviate the symptoms of oppression and improve the quality of life partly . 
INTRODUCTION
CASE PRESENTATION
DISCUSSION
CONCLUSION