Interdigitating cells in the peritumoral infiltrate of laryngeal carcinomas: an immunocytochemical and ultrastructural study.

Interdigitating cells (IDCs) have been found in the peritumoral infiltrate of 18 patients with squamous cell carcinoma of the larynx. These cells have a dendritic shape and are characterized by the expression of S-100 protein and CD1a antigens. By electron microscopy, these cells are seen to establish intimate contacts with the apposed lymphocytes, which sometimes show signs of functional activation and proliferation. These findings indicate that IDCs may play a role in setting up a T-cell immune reaction against neoplastic cells, which may influence the biological behaviour and/or local growth of the tumour. Moreover, monocytes and cells with intermediate features between monocytes and IDCs are also found in the peritumoral infiltrate, thus suggesting that IDCs differentiate in situ from monocytic precursors, possibly under the influence of either tumour-derived factors or the local lymphoid microenvironment.