Histologic morphology and cell-specific expression of fibronectin in control and mCMV-infected NB+12 SMGs. A-E. Histologic analyses. F-H. Fibronectin (FN) immunolocalization. Control SMGs (A) are composed of densely packed, branched epithelial ducts and pro-acini (e) surrounded by fibromyxoid stroma. mCMV-infected SMGs (B-E) show significant viral CPE in the stroma and epithelial dysplasia. There is a notable decrease in branched epithelia (e), hyperplastic and pseudostratified epithelial ducts with dilated lumina, abnormal multilayered epithelial islands lacking a distinct BMZ and reduced cell-to-cell junctions, and there appears to be an admixing of the basophilic stromal and pro-acinar epithelial cells (double black arrows). Abnormal epithelial islands are embedded in a hypercellular stroma (*) composed of 2 distinct cell types: small eosinophilic cells and large basophilic, pleiomorphic cells. Kidney-shaped nuclei pathognomonic of mCMV infection (black arrowheads) are seen in abnormal stromal and ductal cells. F-H. FN immunolocalization. Control SMGs (F) show a distinct and well-demarcated pattern of FN immunoreactivity at the BMZ (white arrow). In mCMV-infected SMGs (G-H), there is a marked shift in FN immunostaining: immunodetectable FN surrounds individual metaplastic stromal cells (white arrowheads) and is nearly absent from epithelial BMZ (double white arrows). FN immunoreactivity is also seen filling ductal lumina. Bar: A-D, F-H- 50 μm; E- 60 μm.