Malignant Mesothelioma of the Tunica Vaginalis Testis in a Patient with HIV: A Case Report

Abstract

Background: Malignant mesothelioma of the tunica vaginalis testis (MTVT) is exceptionally rare, comprising less than 1% of all mesotheliomas and often presenting as hydrocele or non-specific scrotal swelling. Asbestos exposure is recognised, but some cases occur without identifiable exposure, suggesting additional pathways, including chronic inflammation and immune dysregulation. We describe MTVT in a patient with HIV infection and no reported asbestos exposure. Case Presentation: A 73-year-old HIV-positive man presented with a several-month history of progressively enlarging, painless left hydrocele. Examination revealed a transilluminable scrotal swelling without a palpable solid component or inguinal lymphadenopathy. Scrotal ultrasonography demonstrated multiple echogenic, non-mobile solid foci arising from the tunica vaginalis, with increased vascularity on Doppler assessment and preserved testicular parenchyma. Tumour markers were not elevated, and staging imaging showed no lymphadenopathy or metastatic disease. Scrotal exploration identified multiple firm pale-yellow nodules studding the tunica vaginalis. Frozen section raised concern for malignant mesothelial neoplasia, prompting conversion to radical inguinal orchidectomy with high cord ligation. Histopathology confirmed diffuse, multifocal biphasic mesothelioma of the tunica vaginalis, with clear surgical margins, retained BAP-1 expression, and no lymphovascular invasion. Post-operative management consisted of multidisciplinary review, optimisation of HIV care, and structured radiological surveillance. Conclusion: This case emphasises that MTVT may arise without reported asbestos exposure and should be considered when hydrocele is accompanied by tunica vaginalis nodularity or vascular solid foci. HIV-associated immune dysregulation is biologically plausible but cannot be inferred as causal from a single case.