Disseminated thoracoabdominal splenosis mimicking metastatic disease: A case of colorectal cancer

Here, we describe a patient with a history of colorectal cancer in whom 2-[18F]fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography ([18F]FDG PET/CT) was performed for the evaluation of response to therapy. [18F]FDG PET/CT showed a small residual disease in the rectum. In addition, multiple metabolically inactive soft tissue densities were demonstrated in the left hemithorax and the left upper abdominal region, previously interpreted as metastases on computed tomography. Furthermore, bizarre-shaped soft tissues were visualized in the anatomical location of the spleen. Hence, splenosis was suspected. Subsequently, the patient underwent [99mTc]Tc-denatured red blood cell ([99mTc]Tc-DRBC) scintigraphy, which confirmed the diagnosis of extensive thoracoabdominal splenosis.