Thoracic splenosis initially misdiagnosed as lung neoplasms: An unusual case and literature review

OBJECTIVE: Thoracic splenosis, implantation of autologous splenic tissue into the chest after diaphragmatic splenic injury, is rare and frequently mistaken for malignancy, leading to inappropriate treatment. This case highlights the risk of misdiagnosing post-traumatic thoracic splenosis as lung cancer. CASE REPORT: A 69-year-old smoking male patient presented with 1 month of thoracic pain; computed tomography revealed a 3.3 cm left lower-lobe mass suspected as lung cancer. For the past 20 years, he underwent splenectomy after splenic and diaphragmatic injury following a severe motor vehicle accident. Normal tumor markers and history of splenic trauma raised suspicion. Computed tomography-guided biopsy showing splenic red and white pulp (Immunohistochemistry: CK⁻, Vimentin⁺) confirmed thoracic splenosis and averted needless surgery. Pain was attributed to severe coronary disease. The mass remained unchanged at 21-month follow-up and no infective complications have occurred. CONCLUSIONS: In patients with prior splenic trauma, recognizing thoracic splenosis before invasive procedures can secure the diagnosis and avert unnecessary surgery.