Pseudoprogression in Rectal Gastrointestinal Stromal Tumor

Abstract Although gastrointestinal stromal tumors (GISTs) are common mesenchymal intestinal neoplasms, rectal GISTs are rare mesenchymal tumors of the GI tract. We describe a case of rectal GIST in a 63-year-old male. The patient was given imatinib monotherapy and was further followed up by contrast-enhanced computed tomography abdomen for response assessment. We conclude that although rectal GISTs are extremely uncommon, it should be considered as a differential when any rectal mass is incidentally detected. Oncologists and radiologists should also be aware of pseudoprogression phenomena of GISTs in evaluating tumor response.