Thoracic splenosis: a great mimic diagnosed by functional imaging.

Splenosis is defined as the heterotopic implantation of functional splenic tissue in extra-splenic compartments, usually secondary to traumatic or iatrogenic splenic rupture (1). Although it is most commonly found in the abdominal and pelvic cavities, implants have been reported in less common sites such as the thorax, liver, and subcutaneous tissue. Thoracic splenosis represents a diagnostic challenge, as it is usually an incidental finding, rarely symptomatic, and, from an imaging standpoint, can mimic malignant entities such as primary neoplasms or metastatic disease. We present two cases of splenosis diagnosed using nuclear medicine techniques, including the case of a 65-year-old woman with a history of gunshot wound, who required laparotomy, splenectomy, and left nephrectomy, in whom benign pleural and abdominal lesions were identified. Initial metabolic characterization using PET/CT and subsequent confirmation with 99mTc-HDRBC (Heat-Damaged Red Blood Cells) scintigraphy allowed us to establish the definitive diagnosis, avoiding unnecessary invasive procedures. Additionally, we describe a 58-year-old male with a history of blunt chest trauma and prostate cancer, in whom 18F-PSMA PET/CT suggested malignancy, but 99mTc-HDRBC scintigraphy confirmed multi-compartmental splenosis. This report highlights the importance of considering splenosis in the differential diagnosis of thoracic and abdominal nodular lesions in patients with a history of splenic trauma, as well as the value of functional imaging techniques in its accurate identification.