A malignant omental extra-gastrointestinal stromal tumor on a young man: a case report and review of the literature.

Background: Gastrointestinal stromal tumors (GIST) are uncommon intra-abdominal tumors. These tumors tend to present with higher frequency in the stomach and small bowel. In fewer than 5% of cases, they originate primarily from the mesentery, omentum, or peritoneum. Furthermore, these extra-gastrointestinal tumors (EGIST) tend to be more common in patients greater than 50 years of age. Rarely do EGIST tumors present in those younger than 40 years of age.

Case Presentation: We report a case of a large EGIST in a 27-year-old male. An abdominal pelvic computerized tomography imaging demonstrated an intra-abdominal mass of 22 cm, without invasion of adjacent viscera or liver lesions. This mass was resected en bloc with its fused omentum and an adherent portion of sigmoid colon. Pathology results demonstrated a malignant gastrointestinal stromal tumor with positive CD117 (c-kit) staining, and negative margins of resection, and no continuity of tumor with the sigmoid colon. Due to the malignant and aggressive nature of this patient's tumor, he was started on STI-571 as adjuvant chemotherapy.

Conclusion: Stromal tumors of an extra-gastrointestinal origin are rare. Of the reported omental and mesenteric EGISTs in four published series, a total of 99 tumors were studied. Of the 99 patients in these series only 8 were under 40 years of age, none were younger than 30 years old; and only 5 were younger than 35 years old. Our patient's age is at the lower end of the age spectrum for the reported EGISTs. Young patients who present with an extra-gastrointestinal stromal tumor (EGIST), who have complete resection with negative margins, have a good prognosis. There is little data to support the role of STI-571 in adjuvant or neoadjuvant therapy after curative resection. Given the lack of data, the use of STI-571 must be individualized.