[ENTERIC ADENOCARCINOMA DIAGNOSED VIA IMMUNOHISTOCHEMISTRY AND GENOME TESTING OF A PORT SITE MASS AFTER ROBOT-ASSISTED LAPAROSCOPIC RADICAL PROSTATECTOMY: A CASE REPORT].

A 70-year-old man with prostate cancer (cT3aN0M0), with a prostate-specific antigen (PSA) level of 38.9 ng/mL, and a Gleason score of 4+4 = 8, was treated with maximum androgen blockade for 1 year, resulting in a PSA reduction to 0.1 ng/mL. He subsequently underwent robot-assisted laparoscopic radical prostatectomy (RARP). Pathological examination revealed pT3bN1with negative surgical margins. Postoperatively, without additional treatment, PSA levels were 0.007 ng/mL and 0.019 ng/mL at 2 and 5 months, respectively. Six months after surgery, the patient developed left hydronephrosis with upper ureteral urine leakage but no signs of ureteral cancer. However, PSA slightly increased to 0.055 ng/mL, whereas carcinoembryonic antigen (CEA) levels increased to 19.2 ng/mL. Despite this, gastro-colonoscopy failed to detect any evidence of cancer. Nine months after surgery, multiple lung tumors, a solitary hepatic tumor, intraperitoneal lymphatic swellings, and port site masses were identified. Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography scan did not reveal any other malignancies. At that time point, PSA increased to 0.185 ng/mL, while neuron-specific enolase and pro-gastrin-releasing peptides levels were within normal limits. Subsequent gastro-colonoscopy did not detect any malignancies. Ten months after surgery, bilateral orchiectomy and docetaxel chemotherapy were initiated for recurrent prostate cancer with aggressive variants but without neuroendocrine differentiation. Immunohistochemistry (IHC) of a biopsy sample from the port site mass suggested enteric adenocarcinoma distinct from the prostatic tissue observed in the original RARP specimen. The metastases progressed, and CEA levels continued to rise despite three cycles of docetaxel chemotherapy. Genomic testing identified KRAS and other mutations, confirming the tumor's compatibility with enteric adenocarcinoma. Fourteen months after surgery, chemotherapy for colon cancer was initiated. Unfortunately, the patient succumbed to respiratory failure 19 months after surgery. In cases of unusual recurrence patterns, as observed in this case, IHC and genomic testing of the recurrent mass can be crucial for accurate diagnosis.