Case report: Coexistence of Conn's adenoma and non-secreting pheochromocytoma in the same adrenal gland

The association between Conn's adenoma and pheochromocytoma is extremely rare; only a few cases have been described. A 52-year-old female with a history of hypertension and diabetes mellitus was referred for primary hyperaldosteronism and a right adrenal mass. Laboratory tests showed normal serum potassium, a high aldosterone-renin ratio, normal levels of plasma free metanephrine, and confirmed ACTH-dependent Cushing's syndrome. An adrenal scan indicated a heterogeneous right adrenal nodule with microcalcifications, measuring 38.5 × 29.5 mm, with a spontaneous density of 25 HU, an absolute washout of 20%, and a relative washout of 16%. A pituitary MRI showed a constitutionally enlarged pituitary compartment without visualization of a microadenoma. Additional investigations revealed a papillary thyroid carcinoma with normocalcemic primary hyperparathyroidism. Initially, a total thyroidectomy with lymph node dissection was performed, which was complicated by postoperative hypocalcemia. Subsequently, a right adrenalectomy was performed. Histology confirmed the presence of both Conn's adenoma and pheochromocytoma with positive immunohistochemistry for chromogranin A. Although immunohistochemistry for ACTH was not available, a positive dexamethasone suppression test after adrenalectomy suggests that ACTH was secreted by the resected mass. This is the first reported case of coexisting Conn's adenoma and non-secreting pheochromocytoma. The simultaneous presence of these two neuroendocrine tumors may be coincidental or may indicate a genetic predisposition to endocrine dysplasia, or an interaction between the adjacent medullary and cortical tissues. The possibility of a common etiology for these two endocrine tumors is also considered.