Mixed Corticomedullary Tumors of the Adrenal Gland Harboring Both Medullary and Cortical Properties

Adrenal cortex and medulla are derived from mesoderm and ectoderm, respectively. Mixed corticomedullary tumors (MCMTs), comprising an intimately admixed population of both adrenal cortical cells and pheochromocytes in a single adrenal tumor, are extremely rare and its pathogenesis has remained unknown. Here, we report a case of MCMT whose cells co-expressed cortical and medullary antigens in the same tumor cells.[Case description]A 40-year-old woman was referred to our hospital for investigating Takotsubo cardiomyopathy following resection of uterine fibroids. An abdominal CT scan depicted a 24 mm tumor on her left adrenal gland. Her basal serum ACTH, cortisol levels and urinary cortisol were 13.8 pg/mL, 9.5 μg/dL, and 26.5 μg/day respectively. The cortisol level was normally suppressed by an administration of 1 mg dexamethasone (1.4 μg/dL). Plasma renin activity, aldosterone levels and urinary aldosterone were 15.0 ng/mL/h, 122 pg/mL, and 5.0 μg/day, respectively (with administration history of azosemide). On the other hand, her plasma adrenaline and noradrenaline levels were elevated as high as 177 pg/mL and 536 pg/mL, and urinary metanephrine and normetanephrine were 2.12 mg/day and 1.10 mg/day. A 123I-metaiodobenzylguanidine scan revealed high uptake in the tumor. After adequate adrenergic α-receptor blockage, left adrenalectomy was performed. Her postoperative endocrine and clinical findings were normalized without any further complications.[Pathology] Immunohistochemistry (IHC) revealed the presence of MCMT. Cells morphologically consistent with pheochromocytoma and adrenocortical cells were confirmed by immunostaining of chromogranin A and SF-1, respectively. Chromogranin A-positive medullary-derived and SF-1-positive cortical-derived tumor cells were intermixed in the chimeric fashion. In addition, some tumor cells were positive for both proteins, indicating hybrid nature of the cells. Tumor cells of cortical origin expressed CYP11β1, 3β-HSD, p450c21, and p450c17, but not CYP11β2. Non neoplastic adrenal cortex were atrophic, whereas the glomerulosa was hyperplastic positive for CYP11β2, consistent with diffuse hyperplasia and adrenal medullar unremarkable. [Conclusions:]The adrenal tumor was clinically diagnosed as pheochromocytoma, but the pathological findings did reveal cortisol production in the tumor and aldosterone overproduction in the accompanying cortex. This is the first case of MCMT co-expressing adrenal medullary and cortical antigens in the same tumor cells as hybrid cells.