Paratesticular metastasis from colorectal adenocarcinoma presenting as hydrocele: a rare case report and literature review

Colorectal cancer, with the liver being the most common site of distant metastasis, followed by the lungs and bones. Although reports of metastasis to the testis exist, paratesticular metastasis is extremely rare. A 37-year-old male presented with scrotal swelling. Ultrasound revealed hydrocele of the tunica vaginalis. The patient underwent routine surgical treatment, and postoperative pathology of the tunica vaginalis indicated adenocarcinoma of gastrointestinal origin. Colonoscopic biopsy confirmed adenocarcinoma of the sigmoid colon. After six months of systemic therapy, tumor reduction surgery was performed in conjunction with tunica vaginalis excision. Postoperative pathology suggested histological similarity in both sites, with immunohistochemistry results supporting the diagnosis of sigmoid colon adenocarcinoma metastasizing to the tunica vaginalis. We conducted a literature review, summarizing and discussing clinical presentations, metastatic pathways, and diagnostic approaches.