Malignant mesothelioma of the tunica vaginalis

Definition

Epidemiology

Paratesticular mesothelioma arising from the tunica vaginalis accounts for less than 1% of all mesotheliomas but is the second most common paratesticular malignancy. The tumour occurs in older men. Up to half of all cases are associated with asbestos exposure3, often with a long latent period.

Clinical features

Presentation is usually with a hydrocoele.

Histopathology

Most cases show a purely epithelioid morphology, with a combination of tubulopapillary and solid architectures. A minority are biphasic. One one purely sarcomatoid case has been reported2.

Immunohistochemistry

Immunoreactivity resembles that of pleural mesothelioma, possibly with more variable CK5/6 reactivity:

Ultrastructure

There are long slender microvilli, as in pleural mesothelioma.

Differential diagnosis

• Mesothelial hyperplasia shows no invasion

• Papillary serous neoplasms show broader papillae: they express BerEP4 and CEA but may also be positive for WT1, calretinin and CK5/6.

• Rete tumours: also produce nodules studding a hydrocoele. 25% of cases are positive for CEA. They may be positive for calretinin and thrombomodulin but are negative for WT1.

• Epididymal tumours consist of tall columnar cells with clear cytoplasm.

• Metastatic carcinoma, most often of lung or prostate.

References

1 Winstanley AM, Landon G, Berney D, et al. The Immunohistochemical Profile of Malignant Mesotheliomas of the Tunica Vaginalis: A Study of 20 Cases. Am J Surg Pathol 2006; 30:1-6

2 Eimoto T,Inoue I. Malignant fibrous mesothelioma of the tunica vaginalis: a histologic and ultrastructural study. Cancer 1977; 39:2059-66

3 Attanoos RL,Gibbs AR. Primary malignant gonadal mesotheliomas and asbestos. Histopathology 2000; 37:150-9

This page last revised 21.1.2006.

©SMUHT/PW Bishop