Dendritic cells in precancerous lesions of the larynx

Objectives: Hyperplastic lesions of the laryngeal mucosa can eventually develop into squamous cell carcinoma. The relationship between dendritic cell. infiltration of head and neck cancers and prognosis is well known. Surprisingly, data regarding dendritic cell infiltration in precancerous lesions are not available today. It was the purpose of our study to extend these observations and to investigate in more detail the density and distribution of dendritic cells in precancerous lesions. Study Design: Retrospective survey by immunohistochemistry. Methods: For this study we investigated paraffin-embedded tissue sections of 41 specimens, Histological diagnosis disclosed precancerous lesions of the larynx in 34 cases and in 7 cases, squamous cell carcinoma. Immunohistochemical study was performed using antibodies against the cell surface markers S-100, HLA-DR, CD20, CD45 RO, CD45 RA, and Lag. Typical dendritic cell distributions of the immunostained specimens were photographed and measured on a quantitative basis. The medical histories of the patients were then analyzed retrospectively. Results: HLA-DR+ cells could be detected in 14 of 16 cases in mild dysplastic lesions. The infiltration of the dysplastic lesions was sparse compared to cases with higher-graded dysplastic lesions. The distribution patterns of the dendritic cells in specimens with severe dysplastic lesions, but squamous cell carcinoma were extremely similar and markedly different from those in grades I and II specimens. Memory T lymphocytes (CD45 RO+) were detected more often in the group with severe dysplastic lesions (8 of 9 cases) than in the group with squamous cell carcinoma (3 of 8 cases). The inverse became evident for CD20 and CD45 RA immunolabeling. Conclusions: Few dendritic cells were found in the precancerous lesions, This may suggest that these early lesions (grades I and II) are not efficiently monitored by the immune system. Therefore they may develop into carcinomas unimpaired by cytotoxic T cells. As the degree of malignancy rises (grade III), more dendritic cells infiltrate the tumor.