NUMEROUS EOSINOPHILIC GLOBULES (SKEINOID FIBERS) IN A DUODENAL STROMAL TUMOR - AN EXCEPTIONAL CASE SHOWING SMOOTH-MUSCLE DIFFERENTIATION

A unique case of duodenal stromal tumor in a 51-year-old man is report ed. The tumor histologically showed spindle cell proliferation and num erous eosinophilic globules. Most globules were composed of tangled 45 nm thick fibrils, which were ultrastructurally identical to 'skeinoid fibers'. The presence of glycogen granules in the tumor cells and the immunoreactivity for cw-smooth muscle actin suggested smooth muscle d ifferentiation. Focal ultrastructural findings also supported the smoo th muscle nature of this tumor. There were no immunohistochemical and ultrastructural features indicating neural differentiation. In previou s studies, the presence of such 'skeinoid fibers' was suggested to be a histological marker for neural differentiation in gastrointestinal s tromal tumor. However, the findings in the present case suggest that n umerous 'skeinoid fibers' can be identified in duodenal stromal tumor with smooth muscle differentiation, although this condition may be rar e.