Expression of cytokeratins and additional markers in undifferentiated lymph node metastases of the neck

Objective. A variety of carcinomas (CA) can metastasize to the lymph nodes of the neck. Differentiation of CA in the lymph nodes according to their re semblance to the structure of origin is the basis of histopathological diag nosis. However, during the course of the disease, e.g tumor recurrence afte r ablative surgery, these tissues can completely lose the ability to imitat e typical structures of the organ that gave rise to malignant transformatio n. This can result in the inability of the pathologist to identify the orig in of the metastases. The identification of the large group of cytokeratins (CK) as a member of the family of intermediate filaments has improved the diagnosis of epithelial tissues. An attempt was made to use CK antibodies t o identify the organ of origin of poorly differentiated and anaplastic lymp h node metastases of the neck. Methods. We investigated 34 routinely fixed (formalin/paraffin) lymph node metastases of the neck ol specimens of these metastases. The tumors differed in terms of suspected primary tumor site a nd differentiation. Depending on the case history, diagnosis was performed by hematoxylin-eosin staining and by immunohistochemical staining of sectio ns using antibodies against CK (CK nos. 1-10-11, 5-6, 6-8, 7, 8, 8-18, 13-1 5-16, 19 and 20) and against additional markers [vimentin, leukocyte common antigen (LCA), S-100, gross cystic disease fluid protein (GCDFP) and Epste in-Barr virus-induced latent membrane antigen (EBV-LMP)]. Results. The hist opathological diagnosis was lympho-epithelial CA (8 cases), thyroid gland C A (2 cases), mammary gland CA (5 cases), bronchial CA (4 cases), basaloid C A (3 cases), cleat cell CA (2 cases), sebaceous CA (1 case) and pharyngeal CA (9 cases). Some metastases were anaplastic in differentiation (G3-4). Th e marker expression in the immunohistological sections supported the histop athological findings. In some cases diagnosis succeeded especially in evalu ating the marker expression. For example, in lymphoepithelial CA the epithe lial tumor cell formations were positive for CK 5-6 antibodies, while expre ssion in the lymphatic cells was lacking. In mammary gland CA the tumor cel ls were clearly identified by their positivity for CK 7 and GCDFP antibodie s, in contrast to the negative infiltrating cells surrounding the tumor cel ls. Conclusions. In light of the case history details and the histopatholog ical findings, immunohistological expression of various markers, especially the identification of CK subtypes, supported the differential diagnosis. I n some cases the diagnosis may be established only by using CK profile and additional markers.