Case Report

Malignant mesothelioma of the tunica vaginalis: a case with an unusually indolent course following radical orchidectomy and radiotherapy
1J L HARMSE, 1A T EVANS and 2P M WINDSOR

Directorates of 1Pathology and 2Radiotherapy and Oncology, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK

Abstract. Malignant mesothelioma (malignant adenomatoid tumour) of the tunica vaginalis testis is a very rare neoplasm with highly aggressive biological behaviour. Treatment is di¤cult, and widespread local invasion and/or metastatic disease at presentation are associated with a poor prognosis. In this case report we describe for the first time a patient who, despite presenting with locally advanced disease, remains well 10 years after diagnosis and treatment with radical orchidectomy and high dose radiotherapy.

Case report
A 70-year-old man presented in November 1988 with a right scrotal mass. A right hydrocele had been repaired 18 years earlier, but otherwise there was no significant medical or surgical history. On examination, three cysts were palpable above the right testicle, but the organ itself was hard and craggy, which suggested the possibility of a tumour. In view of this, a radical orchidectomy was performed as the primary procedure.

The orchidectomy was performed through an inguinal incision. When the testicle was examined, the lower pole was found to be adherent to the over-lying dartos muscle and skin. A disc of skin and muscle tissue was excised in continuity with the testicle and the specimen was submitted for histo-pathological examination.

Pathological Findings
Macroscopic
The specimen comprised the right testis together with coverings and attached spermatic cord. On section a tumorous mass was seen arising from the tunica vaginalis, and consisting of dense white tissue. An adherent disc of skin and dartos muscle was included and this appeared to be widely infiltrated by pale tumour.

Microscopic
Sections from the tumour showed tubular and glandular structures set in a fibrous stroma. The gland spaces were lined by cuboidal epithelial cells displaying cytological features of malignancy and a brisk mitotic rate (Figure 1a). The tumour
invaded the testicular parenchyma and overlying muscle and skin (Figure 1b). In places, perineural invasion was a conspicuous feature (Figure 1c).

The results of previous histochemistry, immuno-histochemistry and electron microscopy examinations, performed in 1988, gave support to a diagnosis of a malignant mesothelioma, and an expert opinion also agreed with this conclusion.
Reviewoftheoriginalhistologyandrecentimmuno-histochemistry with currently available markers confirm the original diagnosis of primary malignant mesothelioma arising in the tunica vaginalis.