Solitary Splenic Metastasis of Lung Cancer Presenting as Benign Cystic Disease

: Solitary splenic metastasis from primary lung cancer is extremely rare. Here, we demonstrated a solitary splenic metastasis of primary lung cancer that was difficult to distinguish from benign cystic disease. A 69-year-old-female was diagnosed as middle lobe lung cancer. Although preoperative abdominal computed tomography (CT) demonstrated a low-density splenic nodule, fluorodeoxyglucose-positron emission tomography (FDG-PET) revealed no fluorodeoxyglucose uptake in the splenic nodule. Therefore, the nodule was diagnosed as benign cystic disease and middle lobe lobectomy was performed. Postoperative pathologic examination demonstrated papillary-predominant adenocarcinoma with mucin, and the tumor was diagnosed as primary lung cancer. However, the splenic nodule continued to increase postoperatively. Splenectomy was undergone 30 months after the pulmonary resection and the splenic tumor was diagnosed as the splenic metastasis of lung cancer. In the 24 months since the splenectomy, no recurrence has been observed in the absence of treatment. Splenectomy was an effective treatment for solitary splenic metastasis of lung cancer in this case. FDG uptake in the splenic tumor was not evident due to marked mucus production.