Overview of Mesothelioma of the Tunica Vaginalis

Mesothelioma of the tunica vaginalis is the rarest form of malignant mesothelioma. The authors of this article state their awareness of only 98 other cases. Different articles have reported slightly different numbers, but the basic truth of these statements refers to the extreme rarity of the disease. Asbestos exposure is the most commonly reported causative factor, but specific conclusions are very difficult with such a small population set to learn from. Histologically speaking, most cases of the disease are of the epitheloid subtype (60-75%), with the biphasic subtype making up the remainder of diagnoses. The authors state that “pure sarcomatous mesothelioma is exceedingly rare.” The average age of diagnosis is 60 years-old and because the disease specifically grows from the tunica vaginalis—the lining that surrounds the testes—it only affects men.

In most cases, the disease remains undiagnosed until the area is operated on or an autopsy reveals the presence of the malignancy after a patient has died. If a patient does present with a testicular issue, the disease is likely to be misdiagnosed for a number of more common conditions. This situation—as is the case with most forms of mesothelioma—means that the malignancy is likely to be in a less treatable state when a diagnosis is finally returned.
Overview of the Case

The authors describe the patient as a 60 year-old man with swelling on the left side of his scrotum. The man smoked for twenty years, but was not occupationally exposed to asbestos. Like all forms of mesothelioma, asbestos exposure is the main indication for this varient, so it is likely that the patient was simply not aware of his exposure to the mineral. Many diagnostic tests returned normal results, but sonographic testing revealed a number of troubling findings, including an enlarged left testicle and a large hydrocele in the left scrotum. A 1.5 x 1 x1.5-cm polypoid mass (polyp) demonstrating “increased vascularity” was discovered in the scrotal wall, and two similar masses were discovered in the tunica vaginalis.

The patient then received a left hydrocelectomy and scrotal exploration and had tissue removed for biopsy. The biopsy revealed mesothelioma of the tunica vaginalis, biphasic subtype. After a left radical orchitectomy and hemiscrotectomy, a 4-cm tumor attached to the tunica vaginalis was discovered. Immunohistochemical analysis conducted on the tumor confirmed the mesothelioma diagnosis.

Further testing revealed that the cancer had metastasized to the retroperitoneal lymph nodes. The patient then began chemotherapy. 21 months after initial diagnosis, PET indicated distant tissue infiltration and CT demonstrated significant metastases in the lungs and mediastinum. After this discovery, the patient was started on another course of chemotherapy.
Color Doppler Sonography

As we stated above, most cases of mesothelioma of the tunica vaginalis are not diagnosed until surgery or autopsy. Due to its rarity, most physicians will not have any experience with the disease and will certainly not be on the lookout for it. Regarding the case under discussion, the authors were able to identify the disease fairly early and were able to start treatment for it soon after discovery—which was almost certainly a factor in the patient’s survival 21 months after initial diagnosis. The authors state that imaging methodologies have traditionally been of limited use, but research into the sonographic representation of the tumor has begun to identify characteristics particular to it. Along with that research, the use of newer technologies in the analysis of tissue structures has also been important. For this particular case presentation, the authors used color Doppler sonography to identify areas of increased blood flow (hypervascularity) in the identified scrotal masses, which indicated the presence of a possible malignancy. Color Doppler sonogrography is an ultrasonic imaging technology that identifies blood flow and represents these varying rates using colors. Many scrotal masses are relatively benign conditions and do not demonstrate increased vascularity, so the use of an imaging technology that is sensitive to increased blood flow can help to differentiate the mesothelioma from other conditions. If a malignancy is suspected, fine needle aspiration or the removal of tissue—in addition or, or instead of, the excision of the affected testicle—can be attempted to definitively determine a diagnosis.
Conclusion

The authors conclude that color Doppler sonography may be an important new tool for the diagnosis of mesothelioma of the tunica vaginalis. Mesothelioma is a very aggressive tumor in all its forms, so early diagnosis and treatment is a key element in maximizing patient survival time. Because the disease is so rare, it is unlikely that studies will be attempted to precisely quantify this technology’s diagnostic value, so case reports such as these remain the best way to learn more about mesothelioma of the tunica vaginalis.