Endocrine Abstracts

Introduction: We present a case investigated due to hypokalemia and diagnosed as rectal neuroendocrine tumor-related EAS.

Case: A 67-year-old woman with weight loss and symptoms of lethargy, abdominal pain was referred due to low serum K⁺ levels. Elevated blood pressure and a rectal mass were detected at physical examination. Low serum K⁺, elevated ALT levels, lymphopenia, neutrophilia and metabolic alkalosis were present. Computed tomography (CT) revealed asymmetrical rectal wall thickening and multiple masses compatible with metastasis in the liver. Diffuse thickening was present in both adrenal glands and nodules compatible with metastases in lungs. Plasma ACTH at 353 pg/ml was detected. Cortisol was not suppressed in 1 mg and 2-day 2 mg dexamethasone suppression tests (DST) (>75 and 61.9 μg/dl respectively). Circadian rhythm was lost together with elevated overnight serum cortisol levels (>75 μg/dl). Pituitary MR was normal. Cortisol level suppression above 50% was not achieved with high-dose DST. Hypokalemia was thought to be associated with EAS. A biopsy taken from the rectal mass stained positive with chromogranin A, synaptophysin and CD56, while ACTH was negative and was reported as a poorly differentiated neuroendocrine carcinoma. The patient died on the 14th day of admission due to widespread metastatic disease and multiple organ failure.

Discussion: Anorectal neuroendocrine tumors are rare causes of EAS (2%). Hypertension and hypokalemia are findings seen in 70–80% of EAS patients. Optimal treatment of EAS consists of removal of the corticotrophin secreting tumor. However, tumor resection may not be curative in widespread metastatic disease. Since only some cells may secrete ACTH, ACTH may not be stained in biopsy specimens taken from the tumor. While prognosis of small (occult) bronchial carcinoids leading to EAS is quite good, prognosis of extrathoracic neuroendocrine tumors with metastatic disease during diagnosis is generally poor.