Extragastrointestinal Stromal Tumor (EGIST) in the abdominal wall: Case report and literature review.

INTRODUCTION: Gastro Intestinal Stromal Tumor (GIST) is the most common mesenchymal tumor of the gastrointestinal tract (GI). GIST that arises primarily outside the GI tract is termed Extragastrointestinal Stromal Tumor (EGIST). To the best of our knowledge, few cases of EGIST in the abdominal wall were reported.

PRESENTATION OF CASE: We present a rare case of EGIST in the abdominal wall of a 57 year-old female patient. The asymptomatic tumor was located in the superior aspect of the left rectus abdominis muscle, measured 5.4 × cm 5.3 × cm 6.9 cm and was well circumscribed. Histological examination showed an epithelioid cell morphology. The mitotic count was 7/50 HPFs. Immunohistochemistry showed diffuse strong CD117 positivity, focal positivity for S100. The tumor was excised and the margins were free of malignancy. The patient was doing well postoperatively and was discharged on STI-571 regimen.

DISCUSSION: Although GIST is the most common mesenchymal tumor of the gastrointestinal tract, a case with EGIST in the abdominal wall is rare. Positive immunohistochemical staining for CD117 is a defining feature of GISTs. A great percentage of EGISTs represent a metastasis from a primary GIST. In our case, the clinical and diagnostic work-up have been proved it to be an EGIST.

CONCLUSION: The existing data on EGIST is insufficient to make a final conclusion regarding the malignant potential and clinicopathological factors of EGISTs that determine patient prognosis. Thus a follow-up for a long period is required. EGISTs should be kept in mind in the differential diagnosis for patients presenting with solid mass of the abdominal wall.