Schwannomas of the gastrointestinal tract: clinicopathological features of 12 cases including a case of esophageal tumor compared with those of gastrointestinal stromal tumors and leiomyomas of the gastrointestinal tract.

We analyzed the clinicopathological features of 12 gastrointestinal (GI) schwannomas and compared them with those of 37 GI stromal tumors (GISTs) and 15 leiomyomas. Grossly, the schwannomas showed rubbery to firm, yellow-white to tan, glistening, and often trabeculated cut surfaces, resembling soft tissue schwannomas. The GISTs were firm to soft or fish-flesh tan, gray-pink, or variegated tumors with a degenerative change, and the leimyomas resembled typical uterine leiomyomas. Histologically, GI schwannomas were moderately cellular tumors with focal significant nuclear pleomorphism and rare mitotic figures. A characteristic peripheral lymphoid cuff was observed in all cases, but was indistinct in two cases. The GISTs were highly cellular spindle cell, epithelioid or, occasionally, pleomorphic tumors with basophilic appearance. Leiomyomas were paucicellular tumors with eosinophilic appearance. Immunohistochemically, schwannomas were S-100 protein- and glial fibrillary acidic protein (GFAP)-positive, but were negative for c-kit, CD34, and smooth muscle actin (SMA). GISTs were all c-kit- and/or CD34-positive, but GFAP-negative. Leiomyomas were SMA-positive and were negative for c-kit, CD34, S-100 protein, and GFAP. The mean Ki-67 index of schwannoma was 0.7, and those of GIST and leiomyoma were 5.9 and 0.3, respectively. The patients with schwannomas and leiomyomas had a favorable outcome, whereas 12 patients with GISTs showed progression and died of disease. The separation of GISTs from schwannomas is clinically important because the former group has a high risk of malignant behavior. GI schwannomas differed from the conventional soft tissue schwannomas in that they had peripheral lymphoid cuffs, lacked fibrous capsule and vascular hyalinization, and rarely showed degenerative changes. GI schwannomas, however, resembled soft tissue schwannomas in many aspects, and the clinical, gross, histological, and immunohistochemical features were different from those of GISTs and leiomyomas.