Primary signet-ring cell carcinoma (SRCC) of the urinary bladder is an extraordinarily rare adenocarcinoma of the bladder with an incidence of less than 0.6% of all bladder malignancy and is typically associated with a poor prognosis.[1] Here, we describe an interesting case of a patient who presented with a recurrence of SRCC in his neobladder with a metastasis to the anterior abdominal rectus muscle who underwent a repeat cystectomy of the neobladder with ileal conduit formation alongside abdominal wall reconstruction using an anterolateral thigh (ATL) flap.

A 50-year-old otherwise healthy man who initially presented 5 years ago with painless haematuria was then diagnosed with SRCC and had a robotic cystectomy with neobladder formation in 2020 with histopathology of pT4N2, high grade. On surveillance imaging, local recurrence was identified within his neobladder and the adjacent rectus abdominis in early 2023 where he was treated with Pembrolizumab immunotherapy that would go on for 2 years. In July 2024, a Transurethral resection of Bladder Tumor (TURBT) of the neobladder was performed that found necrotic signet-ring cell carcinoma with deep invasion. He was then commenced on 7 cycles of carboplatin chemotherapy. He had repeat surveillance imaging in October 2024, that noted the tumor to have increased in size to 45x41x47mm and with marginally smaller known metastatic lesion with the right abdominus rectus anterior to neobladder, measuring 40x47x97mm. The failure of systemic therapy that consisted of carboplatin chemotherapy and pembrolizumab immunotherapy led to the planning of a joint case between urology and plastics surgery for a repeat cystectomy of the neobladder and abdominal wall reconstructive surgery using an ATL flap. Patient’s consent was gained. A review of the literature was performed, patient information and clinical media were collected.

The patient was placed in a supine position. A midline laparotomy incision was made. Circumferential dissection of neobladder including the right rectus muscle was aided by bone cutter and nibbler to free off from the pubic bone and sent for en bloc histopathology which showed nil evidence of pubic bone involvement. Bilateral ureters dissected and mobilized. Neobladder pedicle closed with a vascular stapler. Ileal conduit formed using a new 20cm length of terminal ileum with an Echelon stapler. Bowel continuity restored. Routine Bricker anastomosis performed and urostomy brought to skin. The case was handed over to the Plastics team for the right ALT flap abdominal wall reconstruction. The patient was admitted to ICU for routine monitoring and discharged to the ward after 3 days. He underwent an uncomplicated post-operative recovery in hospital and with the help of multidisciplinary teams he was deemed ready for discharge D10 post op. Post-op histopathology returned as SRCC recurrence within the neobladder and a secondary neuroendocrine tumor within the right abdominal rectus muscle with negative margins.

We describe a rare case in which there is recurrence of SRCC within a neobladder with locally advanced disease into the rectus abdominis that was completely resected with clear margins. Due to the scarcity of literature of bladder SRCC in itself, let alone recurrence within a neobladder, this case report aims to give better understanding on potential management options of resectable disease.