Predictive factors for adrenal metastasis in extra-adrenal malignancy patients with solitary adrenal mass

The adrenal gland is a frequent site for metastasis, and a solitary adrenal mass is often observed during staging workup or imaging follow-up in patients with extra-adrenal malignancy. To create an appropriate management plan, it is essential to distinguish between benign adrenal lesions and metastasis in patients with extra-adrenal cancer having solitary adrenal masses. Therefore, here we evaluated the predictive factors for adrenal metastasis in patients with extra-adrenal malignancy having solitary adrenal mass.

From September 2003 to June 2016, we retrospectively reviewed patients with extra-adrenal malignancy having solitary adrenal mass on a cancer staging workup or follow-up study who subsequently underwent adrenalectomy at our institution. All patients underwent preoperative functional studies; those with positive results were excluded from this study. Characteristics of oncology patients with adrenal mass including age, sex, body mass index, smoking, mass location, mass size, hypertension, diabetes mellitus, precontrast Hounsfield unit (HU), and synchronous or metachronous adrenal mass based on the time of the extra-adrenal cancer diagnosis were analyzed.

Of the total 68 patients with extra-adrenal cancer having solitary adrenal mass, 22 had pathologically confirmed adrenal metastasis. Primary cancers consisted of hepatocellular cell carcinoma (n = 7), renal cell carcinoma (n = 7), lung cancer (n = 4), colon cancer (n = 3), and breast cancer (n = 1). On multivariate analysis, a higher precontrast HU (P = 0.001, odds ratio [OR] = 1.105, 95% confidence interval [CI] = 1.042-1.172), male sex ( P = 0.019, OR = 9.782, 95% CI = 1.462-65.461), and metachronous adrenal mass ( P = 0.007, OR = 11.090, 95% CI = 1.937-63.490) were observed as predictive factors for adrenal metastasis in patients with extra-adrenal cancer having solitary adrenal mass. The cut-off value of precontrast HU to distinguish between metastasis and benign lesions was 36.2 (sensitivity = 81.8%; specificity = 91.3%).

High precontrast HU (> 36), male sex, and metachronous adrenal mass are predictive factors for adrenal metastasis in patients with extra-adrenal malignancy having solitary adrenal mass.