Adrenal Collision Tumor Diagnosed by F-18 Fluorodeoxyglucose PET/CT

Collision tumor is a rare condition in which 2 neoplasms develop in the same area and become intermingled. It is comprised of 2 distinct tissues, with one frequently being a benign entity and the second a malignant metastasis. While uncommonly encountered, collision tumors have been reported in a variety of sites to include the meninges, lungs, liver, bowel, genitourinary tract, and lymph nodes. Their origin is debated with some hypothesizing that the 2 lesions simply occur in contiguity by chance while others propose that the presence of one tumor alters the local environment, making development of a second tumor more likely. We present a 68-year-old woman with a history of left upper lobe adenocarcinoma and ipsilateral hilar lymph node spread of disease (stage IIb). Staging identified an incidental adenoma in the left adrenal gland, which was subsequently confirmed by magnetic resonance imaging (MRI). Several years later, the lesion developed anatomic and metabolic features typical for malignancy, consistent with a collision tumor. Copyright © 2010 by Lippincott Williams & Wilkins.