Primary Malignant Mesothelioma of the Tunica Vaginalis: A Case Report and Review of the Literature.

Primary malignant mesothelioma of the tunica vaginalis is an extremely rare neoplasm, and its diagnosis is often unclear initially due to its nonspecific presentation. We present the case of an 87-year-old gentleman who presented with a left-sided hydrocele that increased in size over seven months, with no associated history of asbestos exposure. On initial ultrasound, he had a benign appearing hydrocele and proceeded to hydrocelectomy, where suspicious lesions were noticed and sent for histopathology. A subsequent radical inguinal orchiectomy was performed. Histopathologic examination revealed malignant mesothelioma, which was positive for calretinin, Wilm's Tumour 1 (WT-1), AE1/AE3, and D2-40 immunohistochemically, from both operations. On postoperative staging, no metastases were seen, and the patient has been disease-free on follow-up after six months. This case illustrates the challenges in reaching the diagnosis of malignant mesothelioma of the tunica vaginalis and emphasizes the importance of timely surgical intervention in the form of radical orchidectomy and histological examination of any uncommon scrotal mass. Ongoing case reporting is needed to guide management, as there are no standard guidelines due to the limited number of reported cases.