Peculiar morphologic characteristics of adrenal veins and similarity to fibromuscular dysplasia of artery: implication of pathogenesis

BackgroundFibromuscular dysplasia (FMD) is a peculiar abnormality of arterial wall with characteristic bead-like features on angiogram that commonly occurs in renal arteries and carotid arteries. The morphologic features of FMD of arteries share significant similarities to those described for adrenal veins. The pathogenic mechanism of FMD remains largely unknown and genetic susceptibility appears important. MethodsWe examined the morphologic characteristics of adrenal vessels to compare with fibromuscular dysplasia and segmental arterial mediolysis. We have retrospectively reviewed 30 cases of adrenalectomy specimens associated with or without adrenal neoplasms including cortical adenomas and pheochromocytomas regarding the histomorphologic features of adrenal vessels within the normal tissue and the tumors. ResultsAdrenal veins showed characteristically asymmetrical muscle bundles in normal adrenal glands in all cases except for one adrenal cortical adenoma in which normal adrenal gland was absent. These morphologic features shared significant similarities with those of FMD of arteries. A spectrum of vascular changes including hyalinization, intimal fibroplasia, myxoid degeneration and atherosis was observed in 10 of the 15 cases of adrenal cortical adenomas and 5 of the 10 cases of pheochromocytomas. Most common complications were hemorrhage/hematoma and thrombosis. There is no statistically significant differences in patients baseline characteristics including race/ethnicity, marital status, blood pressure and body mass index (BMI). ConclusionThe unique vascular changes in adrenal glands and adrenal neoplasms suggests the importance of tissue specific milieu likely related to adrenal hormones/hormone receptors, providing direction of further investigation of pathogenic mechanisms and potentially management of FMD and similar diseases.