ATYPICAL STROMAL CELLS IN INFLAMMATORY NASAL POLYPS - IMMUNOHISTOCHEMICAL AND ULTRASTRUCTURAL ANALYSIS IN DEFINING HISTOGENESIS

The authors investigated 29 cases of sinonasal polyps with atypical st romal cells (ASC), The clinicopathologic features of these lesions wer e of benign inflammatory polyps except for the presence of ASC, Misint erpretation of these cells resulted in contributor diagnosis of sarcom a (rhabdomyosarcoma). Immunohistochemical study of the ASC demonstrate d the presence of actin (smooth muscle and muscle specific), KP-1, and vimentin; no reactivity was seen with desmin, myoglobin, S-100 protei n, or glial fibrillary acidic protein (GFAP). Unexpectedly, cytokerati n reactivity was identified in more than 75% of the cases analyzed, Ul trastructural analysis revealed that the ASC shared morphologic featur es in common with fibroblasts and smooth muscle cells. Based on the li ght microscopic, immunohistochemical, and ultrastructural findings, it was concluded that the ASC represent reactive myofibroblasts and not a neoplastic proliferation, Follow-up data supported this contention i ndicating the absence of an aggressive biological course, Misinterpret ation as a malignant neoplasm might result in unwarranted and unnecess ary therapeutic intervention.