We report on the first case of benign perineurially differentiated
peripheral nerve sheath tumor (
perineurioma) presenting as a
bleeding gastric mass in a 30-year-old, previously healthy woman with no signs or stigmata of
von Recklinghausen's disease or other primary
tumor at time of presentation. Gastric resection specimen revealed an ulcerated moderately cellular mesenchymal
tumor consisting of elongated wavy spindle cells arranged in a fascicular and sheet-like pattern with focal whorling and occasional alternation of dark staining cellular and light staining hypocellular areas.
Tumor cells were strongly immunoreactive for
epithelial membrane antigen, CD56 (N-CAM), and
vimentin, but were negative for S-100-protein and other lineage-specific epithelial, mesenchymal, hematolymphoid, and reticulo-histiocytic markers. CD117 revealed numerous positive staining mast cells, but the lesional cells were not reacting. We presume that the combined histological and immunohistochemical profiles of this unusual
gastric neoplasm are consistent with a diagnosis of
perineurioma with a probably benign biological behavior. To our knowledge, this is the first report of gastric
perineurioma, an extremely rare mesenchymal lesion that should be considered among the differential diagnoses of
gastrointestinal stromal tumor, especially the so-called KIT-negative GIST. Gastrointestinal
perineuriomas might be under-recognized, as our case was initially diagnosed as a benign GIST.