Metastatic Mesothelioma of the Tunica Vaginalis Presenting as Scrotal and Abdominal Nodules: A Case Report and Review of the Literature

ABSTRACT

Mesothelioma of the tunica vaginalis testis (MMTVT) is a rare neoplasm comprising <3% of all cases of malignant mesothelioma (MM). MMTVT derives from the tunica vaginalis testis, an outpouching of the mesothelial-lined abdominal peritoneum that detaches from the abdominal cavity after the descent of the testis. Similar to pleural mesothelioma, asbestos exposure is a known risk factor. However, MMTVT has a better prognosis than pleural mesothelioma. Cutaneous metastases from MMTVT are exceedingly rare. Herein, we describe a case of a 67-year-old man with a history of asbestos exposure presenting with scrotal pain and indurated plaques on his lower abdomen and scrotum. Histologic sections showed a sheet-like dermal proliferation comprising epithelioid cells with necrosis and increased mitotic activity. The clinical and histologic differential diagnosis was broad, including metastatic carcinoma, melanoma, sarcoma, germ cell tumor, hematologic malignancy, neuroendocrine carcinoma, and malignant mesothelioma. By immunohistochemistry, the neoplastic cells were positive for WT1, D2-40, and AE1/AE3, with rare positivity for calretinin, consistent with a diagnosis of mesothelioma. Additional immunohistochemical studies provided no support for the other diagnostic considerations listed above. BAP1 showed retained nuclear expression (normal) by immunohistochemistry. A DNA sequencing panel identified copy number losses in CDKN2A, MTAP, CDKN2B, and NF2, which are frequently identified genetic alterations in malignant mesothelioma. Subsequent testicular imaging demonstrated a diffusely thickened scrotal wall with an enlarged left testicle. Overall, this represents a case of malignant mesothelioma presenting with cutaneous metastases to the scrotum and lower abdomen, with clinical and imaging features suggestive of primary MMTVT. The International Mesothelioma Interest Group recommends using at least 2 mesothelial markers, such as calretinin, WT1, CK5/6 or D2-40, and 2 epithelial markers, such as claudin-4, CEA, MOC-31, as well as a broad-spectrum cytokeratin stain (AE1/AE3) as part of an initial immunohistochemical panel. Metastatic mesothelioma should be included in the differential diagnosis of malignant epithelioid dermal tumors with unusual staining patterns.

Asbestos exposure and malignant mesothelioma of the tunica vaginalis testis: a systematic review and the experience of the Apulia (southern Italy) mesothelioma register

BACKGROUND

Malignant mesothelioma of the tunica vaginalis testis (MMTVT) is a rare disease with a poor prognosis. The diagnosis and management of these lesions are often difficult for pathologists, surgeons, oncologists and occupational physicians. A preoperative diagnosis of malignancy is rarely made, and there is no established effective therapy except orchidectomy.

METHODS

A systematic literature review was conducted among the articles published in the English literature on primary MMTVT. Moreover four cases from the Apulia mesothelioma register are reported here.

RESULTS

Two hundred eighty-nine cases of MMTVT have been reported from 1943 to 2018. Overall asbestos exposure has been investigated only for 58% of all cases reported in this review, while in 41.8% this data are not available. Noteworthy is the fact that in many reports there is not an anamnestic reconstruction of any asbestos exposure. A history of direct occupational, environmental or familial asbestos exposure is found in 27.6% of the cases. The four cases from the Apulia mesothelioma register are all with ascertained occupational exposure to asbestos.

CONCLUSIONS

The true incidence of asbestos exposure in MMTVT is underestimated because of insufficient information reported in older literature. To establish a broad consensus on the causal relationship between asbestos and MMTVT in the scientific community its necessary to analyze the same variables in the epidemiological studies. In general it should be recommended that a positive history of exposure to asbestos or to asbestos-containing materials are at risk for the development of a MMTVT and should be monitored.

Epidemiology of mesothelioma of the pericardium and tunica vaginalis testis

PURPOSE

Malignant mesothelioma most commonly arises in the pleura and peritoneum but also occurs rarely at other anatomical sites with mesothelial tissue, namely, the pericardium and tunica vaginalis testis (TVT). This review provides a better understanding of the epidemiology of mesothelioma of these extrapleural sites.

METHODS

We conducted a systematic review of the epidemiologic and clinical literature on pericardial mesothelioma and mesothelioma of the TVT. We also analyzed U.S. Surveillance, Epidemiology, and End Results cancer registry data to describe incidence patterns of these malignancies.

RESULTS

An etiologic role of asbestos exposure has been hypothesized for pericardial and TVT mesotheliomas, but no analytical case-control epidemiologic studies exist to test this relationship. A substantial proportion of cases with these malignancies report no known asbestos exposure. In large occupational cohorts with heavy asbestos exposures, no cases of pericardial or TVT mesothelioma have been reported. Trends in the incidence of these malignancies do not match those of pleural mesothelioma, which correspond to historical trends of commercial asbestos use. A male preponderance of pericardial mesothelioma is not evident.

CONCLUSIONS

In the absence of analytic epidemiologic studies, the etiologic role of environmental risk factors for mesothelioma of the pericardium and TVT remains elusive.