Splenosis is autotransplantation of splenic tissue following post-traumatic splenic rupture. Splenosis is seen mostly in the abdominal cavity but if there is post-traumatic diaphragmatic rupture and/or a hiatus hernia splenic tissue may gain access to the pleural cavity and become implanted on the pleural surface or, rarely, within the lung, if there is concomitant lung laceration. Thoracic splenosis is almost always asypmtomatic and is usually diagnosed decades following the initial traumatic injury when detected as an incidental finding on a chest imaging study. It always occurs in the left pleural cavity.