Spindle-cell carcinoma of the aerodigestive tract. An immunohistochemical analysis of 21 cases.

Immunohistochemical analysis of 21 prototypic mucosal spindle-cell carcinomas of the aerodigestive tract was performed at the Armed Forces Institute of Pathology (AFIP) to establish the usefulness of selected immunohistochemical markers in distinguishing spindle-cell carcinoma from other mucosal spindle-cell neoplasms. Immunoreactive keratin could be demonstrated in only 13/21 (62%) of cases. Coexpression of keratin and vimentin was demonstrated in 10/17 (59%) of the tumors evaluated for both of these intermediate filaments. All spindle-cell carcinomas lacked S100 protein, which is an immunoreactivity we would expect to find in spindle-cell malignant melanoma, one of the principal considerations in a differential diagnosis. Both alpha-1-antitrypsin (AAT) and alpha-1-antichymotrypsin (ACT) were demonstrated in the tumor cells in all cases. However, albumin had a similar distribution in the tumors, which suggested that passive uptake was a serious confusing factor. The results of this study indicate that AAT and ACT are unreliable markers for distinguishing spindle-cell carcinomas from malignant fibrous histiocytomas.