Efficacy of Nivolumab in Chemotherapy-Resistant Mesothelioma of the Tunica Vaginalis Testis: A Case Report.

backgroundMesothelioma of the tunica vaginalis testis is a rare neoplasm, accounting for less than 1% of all mesothelioma cases. Due to the rarity of this disease, a standard treatment has not been established. Clinical management is generally adapted from the strategies used for pleural mesothelioma. Although immune checkpoint inhibitors (ICIs) have demonstrated efficacy in treating pleural mesothelioma, their role in mesothelioma of the tunica vaginalis testis remains uncharacterized due to a lack of evidence. This is the first report documenting a clinical response to nivolumab in chemoresistant mesothelioma of the tunica vaginalis testis. CASE: A 71-year-old man presented with painless left scrotal swelling and was initially diagnosed with a hydrocele at the referring hospital. One year later, hydrocelectomy revealed partial thickening of the tunica without malignancy. A subsequent magnetic resonance imaging analysis revealed a new intratesticular nodule. Orchiectomy was performed, and the pathological findings revealed an epithelioid mesothelioma. He was referred to Tsukuba University Hospital for further treatment. He also had a history of Self-Defense Force service, which suggested possible asbestos exposure. Imaging revealed pelvic lymphadenopathy with fluorodeoxyglucose uptake in the right external iliac lymph nodes. He received four cycles of cisplatin and pemetrexed every 3 weeks, resulting in stable disease. Bilateral pelvic lymph node dissection was performed and confirmed the presence of metastatic mesothelioma. Nine months after the surgery, bilateral inguinal lymph node recurrence occurred, and he received cisplatin monotherapy because of renal impairment. Despite four additional cycles of cisplatin monotherapy, the disease progressed. Therefore, chemotherapy was discontinued, and nivolumab was administered. Nivolumab resulted in sustained tumor shrinkage. However, after 3 months of treatment, he developed immune-related encephalitis requiring corticosteroid therapy and nivolumab discontinuation. After 16 months of nivolumab initiation, he was dead from the disease.

conclusionThis is the first report documenting the clinical response of a chemoresistant mesothelioma of the tunica vaginalis testis to nivolumab. ICIs are a promising treatment option for this rare and challenging disease.