Invasive poorly differentiated adenocarcinoma of the bladder following augmentation cystoplasty: a multi-institutional clinicopathological study.

Augmentation cystoplasty is a surgical procedure used in the management of patients with neurogenic bladder. This procedure involves anastomosis of the bladder with gastrointestinal grafts, including portions of ileum, colon, or stomach. A rare but important complication of augmentation cystoplasty is the development of malignancy. The majority of malignancies arising in this setting have been described in case reports. A search for cases of non-urothelial carcinoma following augmentation cystoplasty was conducted through the urological pathology files of four major academic institutions. Ten cases were identified, including six cystoprostatectomy/cystectomy, two partial cystectomy, and two transurethral resection of bladder tumour specimens. The mean patient age at diagnosis was 47 years (range 27-87 years). The male:female ratio was 4:6. The tumours tended to present at an advanced stage; four cystoprostatectomy/cystectomy cases were categorised as pT3a, one was categorised as pT3b, and one was categorised as pT4a. Lymph node metastases were present in all cases which had lymph node excision (range 1-16 positive nodes per case). The majority of cases (90%) were predominantly characterised by a poorly differentiated adenocarcinoma with signet ring cell features. Other morphological features included mucinous features (30%), plasmacytoid features (20%), enteric/villous architecture (10%), and large cell undifferentiated morphology (10%). This is the largest study to date on the clinicopathological features of invasive non-urothelial carcinoma of the bladder following augmentation cystoplasty. The tumours are typically poorly differentiated adenocarcinoma, with diffuse signet ring cell features, aggressive, and present at high stage. Further molecular characterisation may provide additional insights into the pathogenesis of this entity.