Complex sentence: It occurs in the absence of pheochromocytoma, neuroendocrine tumors, and carcinoid syndrome, but it looks similar to carinoid syndrome such as facial flushing, aggression, and ADHD.
Split into simpler sentences: It occurs in the absence of pheochromocytoma, neuroendocrine tumors, and carcinoid syndrome. Although it looks similar to carinoid syndrome such as a facial flushing, aggression, and ADHD.