Histopathology. (A) Caudal fin: well demarcated nodular subcutaneous lesion covered by epidermis (HE stain, bar = 100 μm). (B) Oral mass: poorly demarcated multinodular lesion infiltrating the submucosa with several foci of mineralization (arrows) scattered throughout the masses (HE stain, bar = 100 μm). (C) High-power magnification of Figure 2B: severe mononuclear inflammatory infiltrate with a multinucleated giant cell (arrow) containing phagocytized calcium (HE stain, bar = 100 μm). (D) Oral mass: few red rod-shaped extracellular acid-fast bacteria (arrows) and occasional giant cell not containing phagocytized mycobacteria (arrowhead) (ZN stain, bar = 100 μm).