Rare solitary splenic metastasis from a thymic carcinoma detected on fluorodeoxyglucose-positron emission tomography: A case report

BACKGROUND Thymic carcinoma is a rare, aggressive tumor arising from the thymus. In less than 7% of patients with thymic carcinoma, extrathoracic metastases occur in the extrathoracic lymph nodes, liver, and bone. Isolated splenic metastasis can occur but is very uncommon. To date, only 2 cases of splenic metastases from thymic carcinoma have been reported. CASE SUMMARY A 45-year-old man presented with chronic cough, dyspnea, persistent hoarseness and unintentional weight loss 17 kgs in 6 mo. Neck magnetic resonance imaging revealed a large, lobulated, soft-tissue mass measuring 5.4 cm x 6.6 cm x 3.8 cm which involved the left superior mediastinum and supraclavicular fossa. Chest computed tomography (CT) revealed a confluent and lobulated soft tissue mass encased the right brachiocephalic artery, right and left carotid arteries, and left subclavian artery in the mediastinum. A fluorodeoxyglucose-positron emission tomography was arranged for malignancy survey. The image revealed intense fluorodeoxyglucose avidity in a soft tissue lobulated mass occupying the superior mediastinum, over the cystic lesion in the spleen and in few enlarged nodules over the left supraclavicular fossa. CT-guided biopsy of the thymic mass and the ultrasound-guided biopsy of the splenic lesion were consistent with a thymic carcinoma with splenic metastasis. The patient was diagnosed of thymic carcinoma, cT2N2M1b, stage IVb. CONCLUSION A fluorodeoxyglucose (FDG)-positron emission tomography (PET) scan can provide a useful diagnostic value in conjunction with pathological result in evaluating tumor staging. Our case emphasizes the utility of FDG-PET for metastasis detection in thymic carcinoma.