Histological examination of resected tumor tissue. A &B, Histological examination of resected tumor tissue (×200). A, Irregular cells showing tumor tissue invasive growth involving the submucosa. B, Cytoplasm is filled with fine granules in tumor cells. C &D, Immunohistochemical detection of TSH and GH (×200). C, Most tumor cells express TSH (brown). D, Expression of GH in tumorous cells. E &F, Electron microscopy examination of tumor tissue. Numerous round electron dense granules about 100-200 nm in size are seen in the cytosol. Bar = 0.5 μm.