PAX8 and neoplasm: Immunohistochemically, the tumor cells were positive for caldesmon, smooth muscle actin (SMA), Melan‐A, S100 protein, and cluster of differentiation (CD) 56; negative for cytokeratin AE1/AE3, desmin, HMB‐45, CD34, c‐kit, and paired box protein 8 (PAX8); and had a MIB‐1 index of 1%–2% (Figure 2C‐F).