Photomicrograph of an area of the monolayer of a cytologic smear showing proliferation of mesenchymal cells. Although dense groups of cells are unavoidable, there are many mesenchymal cells that are sufficiently spread for evaluation. The monolayer characteristic of the smear is readily apparent by looking at the erythrocytes in the background, where approximately half are touching but no appreciable overlapping is present. Aqueous Romanowsky stain; original magnification, 200X.