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Summary It has been suggested that cytokeratin 13 is a useful marker of malignancy. We examined normal squamous cell epithelia, hyperplasia, dysplasias of various grades, intraepithelial neoplasia and invasive squamous cell carcinomas of the pyriform fossa using K13 and KL1. Positive staining for K13 was seen in all normal or hyperplastic benign epithelia, was inconstant in dysplasia, and intraepithelial neoplasia and carcinoma was negative. KL1 expression is constant and non significant. These results suggest that tumour cells are unable to synthesize keratin 13 a finding which may be valuable in surgical pathology.

We have analyzed lymphocytes infiltrating nasopharyngeal carcinomas, using a combination of immunoperoxidase staining of frozen and paraffin-embedded sections, and immunofluorescence on lymphocyte suspensions recovered from teased tumours. A panel of monoclonal antibodies was used to define lymphocytic subsets on frozen sections of 14 different tumours. The vast majority of peri- and intra-tumoral lymphocytes were stained by OKT3 antibody. In 8 sections, T4 positive cells were largely predominant, while T8 positive cells were the majority in three sections. Twenty-nine paraffin-embedded sections from other NPC patients stained with HNK-1 antibody showed a variable percentage of positive cells reaching 6 to 15% in nine patients. Most HNK-1 positive cells had the morphology of large granular lymphocytes typical of natural killer cells. Double staining experiments on lymphocytes isolated from 7 tumours revealed a constant presence of T3 positive, HLA-DR positive lymphocytes (from 6 to 29% of mononuclear cells), and of lymphocytes coexpressing the T3 and the Tac (IL-2 receptor) antigens (from 5 to 12% of mononuclear cells). Lymphocytes with a phenotype of activated T-cells are thus constantly found in NPC tumours.

The HNK-1 antibody known to define a subpopulation of human lymphocytes with natural killer and killer cell activities was shown to detect a common neuroectodermal antigen. Most tumor lines and paraffin-embedded tumors and normal tissues of neuroectodermal origin were specifically stained by HNK-1. Lines and tissues of other derivations were negative except a trophoblastic tumor line and a percentage of Ewing's sarcomas, whose histogenesis is poorly understood. These data indicate that HNK-1 antibody could be of interest in clinical histopathology but cannot be considered as specific for a lymphocyte subset.