Jejunal stromal tumor with skeinoid fibers or myenteric plexoma: A case report

Small Intestinal stromal tumors with ‘skeinold fibers’ are uncommon stromal tumors with an associated controversial histogenesis. Although their microscopic appearance Is suggestive of a smooth muscle nature, they lack specific smooth muscle features, as evident by electron microscopy and Immunohistochemistry. They also appear to lack features of neurogenic origin because they fail to react with neural/neuroendocrine markers such as S‐100 protein, neuronapecific enolase and chromogranin. It is interesting, nonetheless, to note that the ultrastructural examination of these tumors may show structures reminiscent of neural differentiation, such as cytoplasmic projections, containing occasional membrane‐bound, densecore, neurosecretory type granules, which mimick the long cytoplasmic processes seen In tumors of neural origin. Moreover, the association of these tumors with Von Recklinghausen's neurofibromatosis, as well as the presence of ‘skeinoid fibers’ in proven neurogenic spindle cell neoplasms such as gastrolntestinal autonomic nerve tumors and schwannomas, suggests that these tumors might also be neurogenic In origin and enhances the diagnostic value of ‘skeinold fibers’ as a possible ultrastructural marker of neural differentiatioin. Thus, light microscopic evaluation is clearly Insufficient to accurately diagnose these tumors and to determine their histogenesis, electron microscopic and Immunohistochemical studies being neccesary. In this article the histogenesis of small Intestinal stromal tumors with ‘skeinold fibers’, regarding a jelunal neoplasm In a 63‐yearsld patient, is reviewed. The light microscopic, immunohistochemical and ultrastructural features are described and compared with findings usually seen in all those stromal tumors which may raise a differential diagnosis, such as smooth muscle stromal tumors, gastrointestinal autonomic nerve tumors, schwannomas, paragangliomas and fibrosarcomas.