A black adrenocortical adenoma causing Cushing's syndrome not imaged by radiocholesterol scintigraphy

In a 33-year-old female patient with left adrenal tumour and Cushing's syndrome, adrenocortical scintigraphy with radiocholesterol did not image the tumour nor the suppressed contralateral gland. Histology showed a black adrenocortical adenoma composed only of compact cells; there was no evidence of malignancy. This demonstrates that non-visualization of the adrenal glands in a patient with Cushing's syndrome is not invariably due to adrenal carcinoma. The literature on black adrenal adenomas causing Cushing's syndrome is reviewed.