Mesothelioma of tunica vaginalis of "uncertain malignant potential" - an evolving concept: case report and review of the literature

Abstract

Mesothelioma of tunica vaginalis is a rare neoplasm, typically demonstrating frankly malignant morphology and aggressive behavior. Rare cases of well-differentiated papillary mesotheliomas have also been reported, which, in contrast, demonstrate indolent behavior. There are, however, cases which do not fit into the well-differentiated or diffuse malignant mesothelioma categories and can be considered mesothelioma of tunica vaginalis of "uncertain malignant potential", which is an emerging diagnostic category. A 57-year-old man presented with a neoplasm in a hydrocele sac. The neoplasm was non-invasive, but showed focal complex and solid growth and it was difficult to categorize either as well-differentiated papillary mesotheliomas or malignant mesothelioma. After the initial limited resection, the patient underwent radical orchiectomy with hemiscrotectomy and is alive and without disease progression after 6 years. Documentation of these rare tumors will allow their distinction from true malignant mesotheliomas and will facilitate the development of specific treatment recommendations.

Figure 1

Microscopic features of mesothelioma of uncertain malignant potential of tunica vaginalis. A, Mesothelioma of tunica vaginalis. The smaller of the two resected tumors measuring 0.5 cm in diameter, is shown completely on low magnification (original magnification ×4). B, Both tumors were circumscribed and showed no evidence of invasion; the base of the stalk can be seen in the centre of the field (original magnification ×10). C, Both tumors were composed mostly of papillae with fibrovascular cores, lined by flat to cuboidal and focally columnar cells with bland nuclei. The fibrovascular cores were mostly paucicellular, but focally exhibited myxoid and hyalinized stroma (original magnification ×10). D, Focally, the neoplasm showed more complex growth with confluent cords and trabecullae (original magnification ×20). E, Smaller solid areas with spindle cells were also present (original magnification ×40). F, A single microfocus of coagulative necrosis was found in the larger tumor; this focus appeared in the vicinity of a stalk-like structure, raising the possibility of local torsion or infarct (original magnification ×40).