Spontaneous Mesotheliomas in Fischer Rats—A Histological and Electron Microscopic Study

Abstract

A E S T R A~Seventeen mesotheliomas from 395 untreated male Fischer 344/DuCrj rats were studied by light and electron microscopy to define the morphological characteristics of the tumors. In 16 out of 17 rats, mesotheliomas were observed in the abdominal and/or scrota1 sac, and the other one was localized on the pleura. Grossly, tumors were yellow-brown with various-sized multiple modules growing irregularly over the surface of the serosa. Microscopically, they varied from complex papillary to sessile nodular growths. Tumor cells were cuboidal to polygonal with round to oval nuclei, and were sometimes arranged in tubule-like structures. Occasionally, the cells contained Mowry's colloidal iron positive materials, which were negative following prior incubation with hyaluronidase. Furthermore, intracellular keratins were detected using the peroxidaseantiperoxidase method. Ultrastructural features of tumor cells included numerous microvilli, a basement membrane, junctional complexes, abundant cytofilaments, dilated rough surfaced endoplasmic reticulum cisternae, and a well-developed Golgi apparatus. The morphological characteristics of these tumors in Fischer 344 rats were consistent with those in humans and with experimentally induced counterparts in rats. The histogenesis of these tumors and the variability in their incidence following oral administration of chemical carcinogens is discussed.

Mesotheliomas in Genetically Engineered Mice Unravel Mechanism of Mesothelial Carcinogenesis

“…An incidence of 4.3% (7/395) of genital and serosal mesotheliomas, and only one pleural mesothelioma has been reported in male rats, with a variety of morphological patterns [48]. More recently, 0.2–5% mesotheliomas of the tunica vaginalis (MTV) were classified as epithelioid, sarcomatoid of mixed, consistent with the histologic classification in HMM [49].…”

Induction of mesothelioma by intraperitoneal injections of ferric saccharate in male Wistar rats

“…Although this location is a rare site for primary mesothelioma in humans (Amthor et al, 1988), the testicular serosa may be a susceptible site for some experi- mental animal models (Cabral & Neal, 1983;Tanigawa et al, 1987). Nitrilotriacetate, a chelator, which makes iron 'free' (i.e.…”

Transforming growth factor β production by spontaneous malignant mesothelioma cell lines derived from Fisher 344 rats

“…The morphological features of the F344 rat MM are similar to those of human or asbestos-induced murine MM, but they are more uniform and, typically, show a simple papillary growth of epithelial-type cells [10,23,24,31]. Previously, we established cell lines from rat spontaneous mesothelioma [18].…”