Histochemical Staining for Acid Phosphatase in MCF7 Cells. MCF7 cells were treated in the presence (lower left and right panels) or absence (upper left and right panels) of TNF-α. Control cells exhibit normal morphology for these cells and faint staining for acid phosphatase (AP). Experimental cells, however, display a shrunken cytoplasm and intense AP-positive staining. Magnification: upper left and lower left panels, 40X; upper right and lower right panels, 400X.