An ACTH-producing pituitary carcinoma developing Cushing's disease.

An autopsy case of an ACTH-producing pituitary carcinoma in a 59-year-old man who developed Cushing's disease is reported. The surgically removed pituitary tumor was diagnosed as chromophobe adenoma, however, pulmonary metastases appeared 2 years after the operation. Autopsy revealed a residual pituitary tumor in the sella turcica with systemic metastases to the lungs, liver, pulmonary lymph nodes, hypothalamus, dura mater, and the subarachnoid space of the midbrain and spinal cord. Immunohistochemistry revealed ACTH positivity in the tumor cells. Further immunohistochemical study showed positive high expression of Ki-67 in the tumor removed at surgery as well as in the autopsied tumor. Ki-67 labeling index provided valuable information about the invasive and proliferative potential compared to noninvasive benign pituitary adenoma.