RESUMEN
Objective To explore the diagnosis and differential diagnosis of tricholemmal carcinoma and the significance of expression of cytokeratin(CK)and oncogene protein(c-erbB-2)in it.Method Twenty-two cases of tricholemmal carcinoma were studied with histologic and immunohistochemical tech-niques,and compared with those in squamous cell carcinoma.The neoplastic cells were stained with cytok-eratin-H,cytokeratin-L and c-erbB-2immunohistochemically(S-P method).Results The morphological characteristics of the tricholemmal carcinoma were the lobular structure and sudden keratinization in the cen-ter of the lobule,which were the key points to be differentiated with squamous cell carcinoma.The positive rate of cytokeratin-H of tricholemmal carcinoma was81.8%(18/22),and the positive cells distributed in the middle zone between the keratinized lobular center and tumor cells in the peripheral area,which differed from squamous cell carcinoma.Cytokeratin-L expression was not found in tricholemmal carcinoma.The posi-tive rate of c-erbB-2was50%(11/22)in tricholemmal carcinoma,with positive cells distributed to the mar-gin of the carcinoma cell nests,and increased with the poor differentiation.Conclusions The particular dis-tribution of cytokeratin-H suggests the tricholemmal origin of tricholemmal carcinoma.C-erbB-2may take part in the activation and differentiation of this tumor.