Introduction
Malignant mesothelioma affecting the tunica vaginalis is a rare type of tumor accounting for less than one percent of all mesotheliomas. While malignant mesothelioma of the tunica vaginalis is a clinically less seen malignancy, it poses a difficult diagnostic challenge as it can mimic more common scrotal or inguinal conditions like hydrocele. Despite the application of aggressive surgical procedures and adjuvant therapies, the prognosis for this condition remains unfavorable. Malignant mesothelioma of the tunica vaginalis testis (covering of the testicle), also called para testicular mesothelioma, is an uncommon tumor accounting for less than one percent of all mesotheliomas. Since its initial documentation in 1957, only case reports have been published, with fewer than 300 reported patients globally to date. Most of these cases were incidentally caught during hydrocelectomy surgeries. Due to the infrequency of this disease, the exact epidemiology and risk factors remain unclear. It is also unclear if asbestos exposure does contribute to the etiology of testicular mesothelioma.
What Is Malignant Mesothelioma?
Malignant mesotheliomas are infrequent tumors originating from the coelomic epithelium in different locations, including the peritoneum, pleura, pericardium, and tunica vaginalis testis. Mesotheliomas, especially the ones arising in the tunica vaginalis testis, are only about 0.3 to 5 % of all mesothelial tumors. Based on the cancer registry data in Lithuania, only 10 to 15 cases of mesotheliomas are reported annually. Especially since 1978, there has been only one reported case of pericardial mesothelioma, and as of now, there have been no cases of mesothelioma in the tunica vaginalis testis in Lithuania.
What Are the Clinical Characteristics of Malignant Mesothelioma of the Tunica Vaginalis?
Most of these cases only show general and non-specific symptoms, like a painless lump in the scrotum that also has a notable fluid buildup, even when it is in the advanced stages. There is no understanding of the disease yet, but it is often linked with increased exposure to asbestos and having a long-lasting fluid build-up. Detecting it in its early stages before surgery can be difficult, and sometimes, it can be mistaken for a different condition called epididymitis. Direct contact with asbestos has significantly raised the risk factor for developing this rare condition.
The usual clinical signs of malignant mesothelioma in the tunica vaginalis testis are not clear and can be tricky for doctors to diagnose before surgery. However, doctors must be more suspicious of it in patients who have been exposed to asbestos and those individuals who are having issues with their scrotum.
How Is Malignant Mesothelioma Diagnosed?
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Ultrasound: Ultrasound can show various-sized nodes, and it is also crucial to follow up with a CT (computed tomography) scan to calculate the stage of the tumor, identify any distant spreading of cancer, and especially to qualify the condition of the lymph nodes in the abdomen.
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PET-CT Scan: Prior to a radical left inguinal orchiectomy (surgical removal of the affected testicle), a PET-CT (positron emission tomography - computed tomography) scan of the whole body is especially done to find out if there are any swollen lymph nodes adjacent to it or any metastasis sites (cancer spreading elsewhere).
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Pathological Examination: Alongside physical examinations and diagnostic imaging, confirming the diagnosis of malignant testicular mesothelioma is very crucial which is done through pathological examination. This cancer develops from a specific type of tissue, so it is necessary to conduct immunohistochemical staining to ensure an accurate diagnosis. Malignant mesothelioma is categorized into different subtypes based on its histopathological features, including epithelioid, sarcomatoid, and biphasic types. The epithelial subtype is the most frequently observed in the peritoneal cavity and the tunica vaginalis.
What Are the Treatment Approaches for Malignant Mesothelioma of the Tunica Vaginalis?
Surgery, chemotherapy, and radiotherapy are the most important treatments for malignant mesothelioma of the tunica vaginalis testis. For advanced cases, a combination of the above treatments may be used. In cases of localized tumors, radical inguinal orchiectomy without removing lymph nodes from the abdomen was done. However, if there are any signs of spreading to the inguinal lymph nodes, surgery to eliminate these lymph nodes is necessary.
The effectiveness of additional radiotherapy or chemotherapy is unclear because there have not been more reported cases. Because of the infrequency of this cancer type, surgical options for using radiation and chemotherapy are debatable. Chemotherapy drugs like Pemetrexed and Cisplatin may be given to treat testicular mesothelioma.
What Is the Prognosis of Malignant Mesothelioma of the Tunica Vaginalis?
The mortality rate for testicular mesothelioma is reported to be 53 % over an average follow-up of two years. In reported and treated cases, PET-CT and MRI (magnetic resonance imaging) scans were done, and those showed no signs of the cancer coming back or spreading elsewhere. The metastatic spread pattern in this disease is commonly through the lymphatic route. Lymph nodes in the groin and the retroperitoneum are usually commonly involved. Prognosis is often poor, but there can be a need for aggressive surgical resection along with hemiscrotectomy and inguinal and retroperitoneal lymph nodes.
Conclusion
In short, a diagnosis of the primary malignant tumor of the tunica vaginalis testis can pose significant diagnostic and treatment challenges. Confirming the diagnosis of malignant testicular mesothelioma, usually involves a combination of physical examination, diagnostic imaging tests, pathological examination, and immunohistochemical staining. However, early diagnosis and immediate intervention can help in improving the quality of life of affected patients.
