Unusual microscopic forms of experimental mesotheliomas

A lightmicroscopic study is made on 36 pleural and 68 peritoneal experimental mesotheliomas induced in white rats by intrapleural and intraperitoneal introduction of asbestos dust. The experimental tumors were compared with 10 spontaneous human mesotheliomas (8 pleural and 2 peritoneal mesotheliomas). The analysis revealed 4 types of morphologically specific experimental mesotheliomas, which could not be referred to the classifications used. In this group are included: a) large cell alveolar, b) small cell alveolar; c) adenocystic; d) with squamous metaplasia and keratinization. The observed unusual experimental lightmicroscopic forms of mesotheliomas support the opinion for great plastic abilities of mesothelium, and the presence of squamous metaplasia with keratinization may be a reason for considering it as a variant of epithelium.