INTRODUCTION: Enlarging pulmonary nodules can be benign or malignant in nature. A rare cause of benign enlarging pulmonary nodules is thoracic splenosis. We describe a case of thoracic splenosis following thoraco-abdominal trauma diagnosed by Tc99m sulfur colloid scan.
CASE PRESENTATION: A 35-year-old woman with a 20 pack year smoking history presented for evaluation of abnormal chest radiograph. Nine years earlier, she was involved in a motor vehicle accident resulting in thoraco-abdominal trauma complicated with bilateral pneumothoraces and splenic trauma. At that time, she required bilateral chest tubes and partial splenectomy. Six year later, a CT of the chest was performed to evaluate persistent back pain just inferior to the left scapula. Imaging revealed two left lower lobe pleural-based nodules –with the larger measuring 2.3 by 1.5 cm –thought to result from posttraumatic pleural scarring. No further evaluation was advised. Four weeks prior to her current visit a chest radiograph, part of a pulmonary evaluation prior to abdominal surgery, revealed two discrete nodules in the left lower lung field. She denied any respiratory symptoms, weight loss or night sweats. Follow-up CT scan demonstrated multiple pleural based left lung nodules. The largest one measured 2.7 by 1.7. The spleen, which was located in the left upper quadrant of the abdomen, measured only 2.4 by 2.1 cm. Given the history of splenic trauma, the patient underwent a Tc99m sulfur colloid scan. As expected, Tc99m uptake was seen at the location of the spleen. In addition, Tc99m uptake was also present in the left lower lung field, corresponding to the 2.7 by 1.7 cm nodule on CT. The latter finding was considered diagnostic for thoracic splenosis.
DISCUSSIONS: Fewer than 40 cases of thoracic splenosis have been reported in the literature. The average duration between injury and diagnosis is 19 years –range 9 to 32 years. Thoracic splenosis results from autotransplantation of splenic tissue in the thoracic cavity following concurrent splenic trauma and disruption of the diaphragm. These implants can be diagnosed by tissue biopsy or, non-invasively, with radioisotope scanning, using either Tc99m sulfur colloid or labeled, heat-denatured red cells. Intrathoracic splenosis is a benign process, which is usually asymptomatic. The nodules can grow slowly. Morphologic characteristics on CT are non specific and alternative diagnoses, such as lymphoma and metastatic disease, need to be considered. Concerns for malignancy may lead to unnecessary biopsy procedures. And such removal of intrathoracic splenic tissue –in a patient without a functioning abdominal spleen –may result in asplenia with the associated increased risk for infections. The presence of Tc99m sulfur colloid activity in the left chest of this patient represented splenic tissue and rendered the need for further diagnostic evaluation unnecessary. Diagnosed 9 years following splenic injury, this case represents a relatively early diagnosis of thoracic splenosis.
CONCLUSION: In a patient with a history of abdominal and thoracic trauma, finding pleural based nodules may represent thoracic splenosis. This diagnosis can be confirmed noninvasively using a radionucleotide scan, such as Tc 99m sulfur colloid scan.
DISCLOSURE: Omar Hussain, None.