IMTs are characterized by a submucosal, loose, cellular proliferation of spindled to stellate cells arranged in a storiform to fascicular pattern with a variable component of inflammatory cells. The surface epithelium may be intact, hyperplastic or ulcerated and show reactive epithelial atypia. The inflammatory infiltrate is comprised of mature lymphocytes, histiocytes, plasma cells, eosinophils and scattered neutrophils. The stroma is highly vascularized and ranges from oedematous to fibromyxoid to collage-nous. The vascular component varies from widely dilated medium sized vascular channels to narrow, slit-like blood vessels that can be obsured by the myofi-broblasts and inflammatory cells. Vascular thrombosis is not present. This overall appearance is similar to a reactive process resembling granulation tissue or nodular fasciitis. The myofibrob-lasts are spindled to stellate with enlarged round to oblong nuclei, variable nucleoli and abundant, eosinophilic to basophilic appearing fibrillar cytoplasm. In some examples, the myofibroblasts have a more epithelioid or histiocytoid appearance, including round to oval nuclei, prominent nucleoli and ample cytoplasm. The myofibroblasts may also appear as slender axonal (spider-like) cells with elongated nuclei, inapparent nucleoli and long cytoplasmic extensions
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