Fig. 6

Malignant pleural mesotheliomas found in MWNT-7-treated rats. A Early stage of mesothelioma in a rat of the high-dose group at week 104. The partially thickened area with high cellularity is seen in the mediastinal pleura. B Higher magnification of (A). Growth of mesothelial cells is distinguished from a simple fibrotic lesion (upper half of the photograph). Surface elliptical or polygonal cells appear to be transitioning to fusiform cells. C Later stage of mesothelioma in a rat of the high-dose group sacrificed at week 81. A thick mass covers the RPF and diaphragm. Tumor invasion is apparent in the diaphragm muscle, and the normal components of the RPF are buried in the tumor mass. Arrowhead, fat; asterisk, nerve fascicle. D Epithelioid mesothelioma in the pericardium of a rat sacrificed at week 93 (high-dose group). E Biphasic mesothelioma in the diaphragm of a rat sacrificed at week 81 (high-dose group). The acinar-like structures are mixed with a sheet of spindle cells. F Sarcomatoid mesothelioma in an RPF in a rat sacrificed at week 93 (high-dose group). G Summary of the pleural lesions in all the MWNT-7-treated rats. A schematic view of the pleural structure in the rat is shown on left side. Detailed anatomical structure of the mediastinum is shown in Additional File. 2: Fig. S1. On the right side, individual histological data with the type and location of the lesion are summarized according to the time points and progression of the pathogenesis