Diffuse sclerosing papillary carcinoma of the thyroid gland: immunohistochemical analysis of the local host immune response

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Abstract
Surgical specimens from four patients with diffuse sclerosing papillary carcinoma of thyroid were examined by electronmicroscopy. In addition, immunohistochemical examination using a panel of monoclonal and polyclonal antibodies was carried out in order to investigate the expression of HLA-DR antigen, the presence of Langerhans' cells and the phenotypic characteristics of the inflammatory infiltrate. The ultrastructural study showed that the intraglandular dissemination, typical of this tumour, was due to massive lymphatic invasion. Many Langerhans' cells were observed among tumour cells and in the lymphoid infiltrates in proximity to tumour foci. HLA-DR expression was seen on macrophages, Langerhans' cells, endothelial cells, lymphoid cells, many tumour cells and in some nonneoplastic follicles close to tumour clusters and lymphoid infiltrates. The immunohistochemical analysis of the inflammatory infiltrates showed a high proportion of B- and T-cells, and moderate numbers of plasma cells. Our results suggest that the tumour-specific immune response can give rise to an autoimmune reaction involving non-neoplastic follicles. It is suggested that this could be one of the mechanisms responsible for immunofacilitation of tumour growth.