Gastrointestinal stromal tumor presenting as a hormonally inactive adrenal mass.

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. Rarely, tumors with the same histological and immunohistochemical features arise in organs having no connection to the tubular gastrointestinal tract designated as extra-gastrointestinal stromal tumors (EGISTs). In this article, we report the first case of an EGIST presenting as a hormonally inactive adrenal mass. A 68-year-old woman with a 3-month history of right abdominal pain was clinically diagnosed as having a hormonally inactive right adrenal tumor sizing 15 cm in diameter. This mass and the tightly fixed right adrenal gland were resected en bloc.Histologically, the tumor was composed primarily of monomorphic spindle cells. Mitotic figure was 2–3 per 50 high power fields. Immunohistochemical analysis revealed strong positivity for CD117 (c-KIT) and smooth muscle actin (a-SMA), but negativity for beta-catenin, CD34, pan-keratin,S-100, desmin, and H-caldesmon. Genetic analysis showed no mutations in KIT gene exons 9, 11, 13, and 17,and in exon 18 of the platelet-derived growth factor-2 receptor gene (PDGFR). The patient proved to be tumor-free at the 18-month follow-up. This case under study demonstrates that EGIST should be included in the differential diagnosis of hormonally inactive adrenal tumors.CD117 (c-KIT) immunohistochemistry should be applied in the pathological workup of soft tissue adrenal tumors.This case is an additional example suggesting that the prognosis of even a very large EGIST is not definitely grave.