Objective To analyze the features of onset, clinical pathological characteristics about the primary bladder mucinous adenocarcinoma.Methods From January 1990 to June 2015, we retrospectively reviewed the data from 15 patients diagnosed as primary bladder mucinous adenocarcinoma, including 10 male patients and 5 female patients.Their mean age was 58 years old, ranged from 41 to 78 years old.Among the fifteen patients, the initial symptoms included hematuria in 13 cases, lower abdominal pain in 1 case and urinary irritation symptom in 1 case.The ultrasound and CT scan revealed bladder tumors, which the size ranged from 2 to 6 cm.The location of bladder tumors included front wall in 12 cases, trigone zone in 2 cases and top wall in 1 case.Nine cases was suspected as tumor from urachal remnants.Eleven patients underwent partial cystectomy, three patients accepted the radical cystectomy and one case accepted transurethral resection of bladder tumor (TURBT).Result Pathological diagnosis was bladder mucinous adenocarcinoma in all patients, including nine from urachal remnant and the others from urothelimn.The tumor exhibited the mushroom liked prominence, which was associated with surface ulceration and infiltrated into the depth of bladder.Meanwhile, it was covered with thick mucinous substances.The histologic examination revealed the presence of andenoid structure, composed by various degree of diferenfiated mucinous cells.In cases with adenocarcinomas from urachus, the residue of urachal tissue could be noticed.The bladder mucous was intact or ulcerated.No sign of metaplasia was observed.In the pathological diagnosis, the classification included grade Ⅲ in 3 cases, grade Ⅱ in 7 cases and grade Ⅰ in 5 cases.Ten persons reported the information of the follow up.Eight of them, whose tumor originated from urachus, accepted bladder-sparing surgery.One died from acute myocardial infarction after 23 months postoperatively.And one died from cerebral hemorrhage 45 months postoperatively.The others have been followed up from 8 to 65 months with no sign of recurrence.In two cases with urothelial carcinoma, one was found the new urothelial carcinoma 50 months after TURBT and one died from cancer metastasis 29 months after partial cystectomy.Conclusions Primary mucinous adenocarcinoma of the bladder possess the relatively high malignant tendency.The hematuria is the main initial symptoms.The histologic examination revealed the presence of different differentiated mucinous cells and formed the andenoid structure.The case with urachal remnant adenocarcinoma has the better prognosis than other types.