Prevalence of malignancy in adrenal incidentaloma on CT studies in patients with unknown primary malignancy

Abstract

Background : Cross-sectional imaging has been increasingly used. The adrenal incidentaloma was detected and caused problem to diagnose benign or malignant especially unknown primary cases.

Objective : To determine the prevalence of malignancy in adrenal incidentaloma in patients with unknown primary malignancy.

Setting : Department of Radiology, Faculty of Medicine, Chulalongkorn University/ King Chulalongkorn Memorial Hospital, Thai Red Cross Society

Research design : Retrospective study

Methods : The CT study was retrospectively reviewed from January 2004 to April 2010 to identify adrenal incidentaloma in patients without clinical history of malignancy. The diagnosis of benign adrenal lesion was based on specific imaging criteria. Imaging diagnosis of benign had to be confirmed by its attenuation, washout rate study, 1-year stability in diameter on follow-up CT or MRI or at least 2-years stability on clinical follow-up.

Results : Forty-eight adrenal incidentalomas were included. Histopathology was confirmed for 1 lesion, MRI with at least 1-year stability for 3 lesions, more than 1-year follow-up CT studies for 18 lesions and at least 2-year clinical stability for 26 lesions. One lesion showed slightly increased in diameter but had well-defined margin and low attenuation value on unenhanced CT. Most of the incidentalomas were adenomas, followed by myelolipomas, hematomas, adrenal cortical hyperplasia and disseminated histoplasmosis. No malignant adrenal lesion was identified.

Conclusions : No malignancy was confirmed in patients with adrenal incidentaloma with unknown primary malignancy.