The exact cause of adrenal medullary hyperplasia is unknown. It is often characterized by bilateral adrenal enlargement, which may be asymmetrical and sometimes exhibits nodular changes. CT imaging may reveal increased adrenal size without evidence of tumors. 131I-MIBG scintigraphy can visualize the adrenal medulla, typically showing medullary enlargement, and is useful for evaluations similar to those conducted for pheochromocytoma (PHEO).
For treatment, surgical removal of the more significantly enlarged adrenal gland may be performed. If the therapeutic effect is suboptimal, partial adrenalectomy of the opposite side or treatment with 131I-MIBG may be considered.
Currently, pheochromocytomas and paragangliomas are considered to possess malignant potential. Prognosis is influenced by factors such as patient age, tumor aggressiveness, presence of metastases, family history, and timing of treatment. Benign cases have a 5-year survival rate exceeding 95%, while prognosis is poor for cases with liver, lung, or bone metastases.