Intestine as the Exclusive Site of Distant Metastasis From Lung Adenocarcinoma Detected on 18F-FDG PET/CT

Intestinal metastasis secondary to lung cancer is clinically uncommon. In previously reported cases, it predominantly occurred in patients with advanced-stage lung cancer and widespread systemic metastasis. We report rare ¹⁸ F-FDG PET/CT imaging findings of lung adenocarcinoma with exclusive intestinal metastases in a 77-year-old man. ¹⁸ F-FDG PET/CT demonstrated a moderately hypermetabolic pulmonary nodule and 2 intensely hypermetabolic intestinal lesions. Immunohistochemistry verified these intestinal lesions as metastases from pulmonary adenocarcinoma. Intestine as the exclusive site of distant metastasis from lung cancer is extremely rare and prone to be misdiagnosed as a primary gastrointestinal tumor. ¹⁸ F-FDG PET/CT identified this rare metastatic pattern and uncovered an additional ascending colon lesion, facilitating precise clinical management.