INTRODUCTION:Thoracic splenosis is a very rare entity referring to ectopic splenic tissue in the thorax, usually due to splenic tissue seeding the pleural cavity after thoracoabdominal trauma. It is typically discovered incidentally as an asymptomatic pulmonary nodule or mass, leading to unnecessary invasive investigations.
CASE PRESENTATION:A 47 year old white female with reflex sympathetic dystrophy, was admitted with bilateral lower extremity weakness and dysethesias. During her hospitalization, she underwent a chest CT, which revealed a well defined pleural-based soft tissue mass in the left upper lung zone, measuring 2.5×1.8cm, without lymphadenopathy. Additional soft tissue densities were found in the left retroaortic region, 1.7×3.2cm, and left upper abdomen 3.2×1.7cm. An absent spleen was noted. The patient was a life-long nonsmoker. She initially refused further workup, but a few months later agreed to a transthoracic fine-needle aspiration, which was nondiagnostic. She refused an open lung biopsy, and was lost to follow up. 1½ years later she presented with chest tightness and dyspnea. Pulmonary function studies revealed reversible airflow obstruction. A chest CT performed at this time and six months later showed no interval change from the earlier CT. Further questioning revealed a motorcycle accident 24 years earlier, with thoracoabdominal trauma, necessitating splenectomy. Based on this history, thoracic splenosis was suspected. A technetium-99m labeled sulfur colloid liver spleen study was performed that showed radiotracer uptake in the posterior-lateral aspect of the left chest and abdominal region consistent with splenosis. Retrospective review the previous fine needle aspiration was consistent with thoracic splenosis.
DISCUSSIONS:Thoracic splenosis is a very rare entity, Alaray et al. 2005 reported less than 40 cases described in the literature. Thoracic splenosis refers to ectopic splenic tissue in the thorax, usually due to natural autotransplantation of splenic tissue with seeding in the pleural cavity after thoracoabdominal trauma involving disruption of the splenic capsule. Sites of splenic fragment implantation include more commonly the peritoneal cavity and less commonly the parietal and visceral pleura, pericardium, retroperitoneum and rarely lung and brain. Natural splenosis after splenectomy due to trauma occurs in approximately 1/3 of patients, with reports of this approaching 50%.Thoracic splenosis has only been reported within the left thorax. The splenic implants derive their blood supply from surrounding tissue and grow to mature splenic tissue. Histologically, splenosis has been found indistinguishable from normal splenic tissue. The reticuloendothelial function of the ectopic splenic tissue appears preserved, with peripheral blood lacking Howell-Jolly bodies and damaged erythrocytes. However, the effect on immunologic response remains inconclusive. Thoracic splenosis is typically discovered incidentally as an asymptomatic pulmonary nodule or mass. World et al. 2002 found that 52% presented as multiple nodules. The average reported interval between the trauma and finding splenosis varies from 18.8 to 29 years. This may lead to unnecessary invasive investigations including fine needle aspiration, thoracotomy and exploratory laparotomy. Obtaining a good history is vital. Although rarely symptomatic, symptoms include chest pain, hemoptysis, GI hemorrhage and abdominal pain. Radiographically, CT findings are usually nonspecific round or oval soft-tissue pleural or parenchymal masses. Splenosis can be confirmed using scintigraphy with 111In-labeled platelets, 99mTc sulfur colloid scan, and 99mTc heat-damaged erythrocyte study, which all result in increased radioactive isotope uptake in ectopic splenic tissue.
CONCLUSION:Thoracic splenosis is uncommon, but should be considered in the differential diagnosis of left-sided pleural-based pulmonary nodules, along with vascular-, rheumatologic- and infectious lesions, hamartomas, neoplasms, granulomas, atelectasis, mucoid impaction and infarction. Careful history taking indicating a history of prior thoracoabdominal trauma and splenectomy, followed by confirmatory sulfur colloid scanning is often all that is needed for the diagnosis. Resection is rarely needed unless symptoms of mass effect exist.
DISCLOSURE:Maria Ohman, No Financial Disclosure Information; No Product/Research Disclosure Information