Moderate cellular and nuclear pleomorphism is noted and few mitotic figures, focal hemorrhages and necroses are apparent.
Many tumor cells exhibit strong cytoplasmic PAS positivity which is abolished by diastase digestion.
No pituitary adenoma is found. Strong and diffuse immunopositivity is noted for vimentin. Immunostainings are negative in the tumor cells for neurofilament antigen, epithelial membrane antigen, S-100 protein, glial fibrillary acidic protein, smooth muscle actin and cytokeratin. Electron microscopy demonstrates the presence of thin parallel filamentous bundles in the cytoplasm of tumor cells.