A 49-year-old male patient was admitted to our department due to increased frequency of urination, urodynia, and hematuria for about 11 months. Ultrasonography identified a solid mass with the size of 3.7 cm x 2.6 cm in the anterior wall of the bladder. Computed tomography of the abdomen further showed that the bladder was irregularly thickened. A tumor with the size of 4.0 cm x 2.7 cm x 4.0 cm and progressive annular enhancement was observed in the anterior wall, which extended superiorly up to just below the umbilicus ( Figure 1 ). Cystoscopy identified a cauliflower-like tumor with the size of 4 cm x 4 cm and a broad base on the top wall of the bladder. Diagnostic resection was then performed, and histological analysis revealed that there was bladder adenocarcinoma (predominantly consisting of signet ring cell type) in the excised mass. Immunohistochemistry showed that villin, CK20, CDX-2, and Ki-67 were positively stained in the tumor, while P40, P63, and CK7 were negatively stained. No gastrointestinal tumor was found by gastroscopy, colonoscopy, or gastrointestinal barium.
Radical cystectomy was prepared for this patient according to the above findings. During the surgical exploration, a urachal mass extending from the umbilicus to the dome of the urinary bladder was found. Unfortunately, multiple metastases were seen in the sigmoid colon, terminal ileum, mesentery, and peritoneum, so palliative surgery including partial cystectomy and urachal mass cystectomy was conducted for this patient. Postoperative pathology showed that the tumor consisted of poorly to moderately differentiated adenocarcinoma, including signet ring cell carcinoma and mucinous adenocarcinoma ( Figure 2 ). The carcinoma invaded the subserosal fibrous connective tissue and some area had broken through the serosa. The immunohistochemical results were as follows: CKpan (+), villin (+), CK20 (+), CDX-2 (+), beta-catenin (+), SATB (+), cdh17 (+), CK7 (-), GATA-3 (-), CK5/6 (-), P40 (-), P63 (-), PAP (-), PSA (-), CK7 (-), and Ki-67 (+). In addition, the periodic acid-Schiff stain and mucin carmine staining were both positive in the carcinoma tissue. Postoperative PET-CT identified several metastases in the peritoneum and omentum. The clinical stage for this patient was finally referred to as IVb according to the Sheldon staging system.
Chemotherapy was conducted for this patient after surgery. A chemotherapy regimen (repeated every 21 days) involving fluorouracil (100 mg/m2, civ 96 h, days 1-4) combined with cisplatin (75 mg/m2, ivgtt, days 1-3) was made for this patient. In addition, the patient also received oral anlotinib (10 mg/day on days 1-14 of a 21-day cycle) for targeted therapy. So far, this patient has received 4 cycles of pharmaceutical therapy and is now doing well on regular follow-up. The treatment timeline for this patient is summarized in  Figure 3 .
Tumor biomarkers, including carcinoembryonic antigen (CEA), alpha-fetoprotein (AFP), carbohydrate antigen 72-4 (CA72-4), carbohydrate antigen 19-9 (CA19-9), and carbohydrate antigen 125 (CA125), were detected for this case. CEA was 1.2 ng/ml (normal: 0-5), AFP was 1.9 mug/L (normal: <7), CA72-4 was 11.3 U/ml (normal: 0-6.9), CA19-9 was 9.3 U/ml (normal: 0-39), and CA125 was 145 U/ml (normal: 0-35) in the first month after surgery. In the most recent follow-up, CEA was 1.3 ng/ml, AFP was 2.6 mug/L, CA72-4 was 12.8 U/mL, CA19-9 was 10.3 U/mL, and CA125 decreased to 22.2 U/ml.