Following the histology findings, several diagnoses could be ruled out, including inflammatory myofibroblastic tumors, leiomyosarcoma, tumors of perivascular epithelioid cells (due to negative expression of ALK, smooth muscle actin (SMA), desmin, and HMB45), solitary fibrous tumors, gastrointestinal stromal tumors (negative CD34, CD117, and discovered on GIST-1 (DOG1)), and schwannoma (negative S100) [12]. The gene discussed is KIT; the disease is leiomyosarcoma.