Diagnosis of malignant mesothelioma of the tunica vaginalis testis by ultrasound-guided fine-needle aspiration.

Malignant mesothelioma of the tunica vaginalis testis is a very rare tumor that is not usually diagnosed until surgery is undertaken. In only a few cases has the correct diagnosis been obtained preoperatively by cytologic examination of fluid from the hydrocele. We describe a case of mesothelioma of the tunica vaginalis testis that was suspected on sonography because of the presence of a hydrocele and focal nodularities. The diagnosis was confirmed preoperatively by ultrasound-guided fine-needle aspiration cytology aimed at 1 of the focal nodularities. Our patient was an 85-year-old man with concomitant cancer of the sigmoid colon; because of his age and the spread of his colon cancer, we did not remove the scrotal lesion. We recommend consideration of ultrasound-guided fine-needle aspiration cytology of the solid masses instead of the fluid from the hydrocele in cases of suspected malignant mesothelioma of the tunica vaginalis testis.