Malignant mesothelioma
Malignant mesothelioma arising from the serosal membranes of the tunica vaginalis is rare. Most examples in the published medical literature are individual case reports. This study presents the clinicopathological findings of mesothelioma of the tunica vaginalis in one of the largest series to date. Individuals with mesothelioma of the tunica vaginalis were identified from our institution database, and their clinicopathological features were recorded. A retrospective search of the pathology electronic medical record was performed for paratesticular malignant mesothelioma diagnosed between 1990 and 2020. A total of 28 cases were identified. The morphologic and immunohistochemical features were reviewed. Follow-up information was obtained from physicians’ notes. The median age was 58 years (range, 16-85 years). Nine presented with hydrocele, 4 with testicular mass and one with testicular pain. The latter was incidentally diagnosed on microscopic examination, and no grossly identified tumor. All patients were diagnosed on orchiectomy, except one who was diagnosed on a hydrocelectomy specimen. The clinical presentation of the remaining is unknown. Most but one patient, presented with unilateral tumors; predominantly right-sided (n=18). Follow up data was available for 13 patients (range 2 mon-15 years), 6 had no evidence of disease, 4 died of disease and 3 are alive with metastatic disease. Tumor size was available for 11. The median size was 6.5 cm (range, 1-13 cm). Microscopically, tumors were predominantly epithelioid (n=18) with papillary, tubulopapillary, solid, or tubular architectures. The cells had moderate amounts of pale to eosinophilic cytoplasm with moderate to marked nuclear pleomorphism. The remaining showed a mixed biphasic morphology with epithelioid and sarcomatoid (spindle cell) components (n=9). No purely sarcomatoid tumors were identified. Immunohistochemically, tumors were consistently positive for calretinin, WT1, and podoplanin, while are negative for MOC31, BER-EP4 and OCT3/4. L1CAM was negative all except one (1/8). In summary, Malignant mesothelioma of the tunica vaginalis is rare malignant tumor with poor survival and high propensity for metastasis. Tumors arising within testis and metastasis to the testis should be excluded to establish the accurate diagnosis and careful evaluation of clinicopathologic and immunohistochemical features is required.
