Rectal stromal tumor with an exceptional liver and bone metastatic locations

Abstract

Gastrointestinal stromal tumours (GIST) are rare mesenchymal tumours which represent 1% to 3% of gastrointestinal neoplasm. Rectal location of GIST is extremely rare reaching 5% of GIST and only 0.1% of rectal tumours. They usually metastases to the liver (65%) and exceptionally to the bone (3%). We reported a case of rectal stromal tumour with an exceptional metastasis located in the rib. A 40-year-old man who presented with pelvic pain, associated with rectal syndrome, rectal bleeding and subocclusive episodes. Physical examination objectified a tough, budding rectal mass, with a smooth wall, localized 3cm above of anal margin. A Thoraco-abdominal computed tomography showed a large heterogeneous tissue mass, taking the whole pelvis, coming from the right-side wall of the rectum of 17.3 x 14cm. It was associated with liver and bone secondary locations. Biopsies confirmed the secondary locations of an intermediate risk GIST. Immunohistochemical study showed an overexpression of c-kit protein (CD117) and Dog1. Imatinib was prescribed to reduce the tumour size. Stromal metastatic rectal tumours in bone level are extremely rare conditions. The diagnosis is confirmed by histological examination with immune histochemical analysis. The prognosis remains poor in metastatic forms but it has been improved since the introduction of Imatinib.