RARE-15ACTH-SECRETING PITUITARY CARCINOMA METASTATIC TO THE LIVER IN A PATIENT WITH A HISTORY OF ATYPICAL PITUITARY ADENOMA AND CUSHING'S SYNDROME

Abstract

Pituitary carcinoma is a rare entity requiring the presence of metastasis to confirm its malignant potential. Most examples secrete prolactin or adrenocorticotropic hormone (ACTH). Reported sites of metastasis include to the cerebral cortex, cerebellum, spinal cord, leptomeninges, eyes, heart, lung, lymph nodes, pancreas, liver, kidney, ovary, myometrium and bone. Liver metastasis is most common with prolactin-secreting tumors. In ACTH-secreting tumors it is frequently associated with Nelson's syndrome (rapid enlargement of a pituitary adenoma after bilateral adrenalectomy to palliate Cushing's syndrome). Here we report acase of an ACTH-secreting atypical pituitaryadenoma metastasizing to the liver in a 51-year-old woman with Cushing's syndrome and intact adrenal glands 2.5 years after resection of the primary pituitary lesion with subsequent radiotherapy for residual cavernous sinus disease. Surveillance of ACTH and 24 hour urine cortisol levels revealed that they were significantly elevated to 142 pg/mL (normal range 10-60 pg/mL) and 541 μg/day (normal range 3.5-45 μg/day), respectively. These abnormalities prompted aPET scan which demonstrated a hypermetabolic liver lesion with a maximal SUV of 3.3, which was suspicious for metastasis on MRI. An ultrasound-guided liver biopsy demonstrated involvement by a moderately differentiated carcinoma consistent with a primary pituitary lesion. Nests of tumor cells showed a monotonous epithelioid appearance, abundant cytoplasm and small nucleoli. Immunostains for AE1/3, synaptophysin, and ACTH diffusely highlighted the lesional cells. This case thus represents an additional rare example of an ACTH-producing pituitary carcinoma metastatic to the liver in a patient with Cushing's syndrome and intact adrenal glands.