Case of adrenal incidentaloma in which autonomous cortisol production became clear during a very short term

A 57-year-old woman was admitted to the hospital for the further evaluation of a left adrenal incidentaloma measuring 45 mm x 33 mm. She had no signs of the clinical manifestation of hypercortisolism. An endocrine evaluation revealed that her ACTH level was normal and cortisol values were almost normal pattern excluding the value at 9 PM slightly rising, however, the cortisol was not completely suppressed by the overnight administration of 1 mg dexamethasone. These findings indicated that subtle abnormalities of the hypothalamo-pituitary-adrenal axis were present in this case. After 3 months, surprisingly, the ACTH was suppressed to low levels. Further hormonal investigations revealed that the cortisol level was normal but had an abnormal diurnal rhythm and was not suppressed completely by a 1 mg or an 8 mg overnight dexamethasone dose. Adrenal scintigraphy revealed positive uptake in the left adrenal tumor with no uptake in the right adrenal gland. The patient underwent a left laparoscopic adrenalectomy. Microscopically, the tumor displayed histopathological features in common with ACTH-independent macronodular adrenocortical hyperplasia, including clear cell predominance, a pattern of small compact nests in clear cell areas, and a cord-like arrangement of small compact cells. An in situ hybridization study demonstrated the hybridization signals for P-450scc, 3beta-HSD, P-450c21, P-45011beta, and P-45017a which were observed in the clear cells as well as compact cells, the compact cells being more intensely stained. This case indicates the ability of autonomous cortisol production to become clear during a very short term and a more detailed and careful short-time follow-up should be recommended in patients with adrenal incidentalomas.