Metastatic diseases to the adrenal gland: a comprehensive study from an academic institution with emphasis on clinical occult cases

The adrenal gland is one of the common sites of metastasis and distinguishing metastatic diseases from adrenal primary neoplasms is essential for accurate clinical management of patients. Our study aimed to elucidate the spectrum and clinicopathologic features of metastatic solid tumors to the adrenal gland at an academic institution, with special focus patients presented with solitary adrenal masses without previously known malignancies. Our departmental database (2013-2022) was retrospectively searched and 129 patients with metastatic solid tumors involving the adrenal gland were identified. The median age at the initial diagnosis of metastatic diseases was 64 years old (range, 54-70 years). The majority of the diseases were presented as unilateral (n=118) or unifocal (n=119) involvement. Most patients had known prior or concurrent malignancies (n=125), whereas adrenal gland involvement was the initial clinical presentation in 4 patients. The most common primary carcinomas included renal cell carcinoma (n=84), lung adenocarcinoma (n=21), urothelial carcinoma (n=3) and hepatocellular carcinoma (n=3). In 104 (80 %) patients with available follow up (median of 39 months, ranging 0-81 months), 43 patients died of disease. Metastatic diseases are usually exercised in the differential diagnosis when there is clinically known malignant primary. In patients without clinical known malignancies, close clinical and radiologic correlation and thorough relevant clinical work up are critical, because clinical occult malignancy may metastasize to the adrenal gland as a solitary mass at the initial presentation, although it is rare.