An immunohistochemical and ultrastructural observation in two cases of testicular malacoplakia. Its relationship to granulomatous orchitis.

We report histochemical and immunohistochemical studies of two cases of testicular malacoplakia from 54-year-old (case 1) and 45-year-old (case 2) men and an ultrastructural study of case 1 with review of the literature. The testes were enlarged and the cut surface showed a neoplasma-like appearance. The testicular architecture was destroyed due to replacing by granulomatous lesion consisting predominantly of macrophages with abundant eosinophilic granular cytoplasm (so-called von Hansemann cell) in both cases. In the cytoplasm of von Hansemann cells, PAS-positive inclusion bodies were frequently observed. There was no histochemical evidence of iron or calcium deposition in the inclusion bodies. Immunohistochemically, positive materials for anti-α1-antitrypsin, anti-α1-antichymotrypsin and anti-Escherichia coli (E. coli) antibodies were seen in the cytoplasm of von Hansemann cells in granulomatous lesion. Thus, we considered the inclusion body as Michaelis-Gutmann (M-G) body. Electron microscopically, various kinds of phagosomes, including M-G structures which do not seem to contain calcium, were observed in the cytoplasm of von Hansemann cells in case 1. Although, the pathogenesis of testicular malacoplakia is still unclear, bacterial infection, especially E. coli infection, may be play an important role for the pathogenesis of testicular malacoplakia.