POMC and neoplasm: Although, in both Cases 1 and 2, the selectivity index in the left adrenal vein met the criteria of being ≥2 before ACTH stimulation and ≥5 after ACTH stimulation, indicating successful catheterization, the high cortisol secretion from the tumor side may have masked the potential failure, leading to an underestimation of aldosterone levels from tumor side.