Tumor-infiltrating lymphoreticular cells. Histologic and immunohistologic investigations performed on metastasizing squamous cell carcinomas of the head and neck.

Ten squamous cell carcinomas of the head and neck region and metastatic deposits in 41 cervical lymph nodes were investigated histologically and immunohistologically to determine the cellular immune response to the tumors, particularly the localization and phenotype of the tumor-infiltrating lymphoreticular cells. The lymphoreticular cells were accumulated preferentially in the stroma in and around the tumor. The foci of neoplastic cells usually contained smaller numbers of lymphoreticular cells. Lymphocytes and macrophages that lay in close contact with malignant cells did not exert histologically apparent signs of toxic effects on these cells. Macrophages (Ki-M6+) nearly always constituted the largest fraction of the lymphoreticular cells, but T-lymphocytes (Leu-1+), T4-cells (Leu-3a+), and plasma cells were also often observed in large numbers. T8-lymphocytes (Leu-2a+) and T-accessory cells (Leu-6+) most often occurred in moderate numbers. Leu-6+ cells represented the only cell type found predominantly in the atypical epithelial complexes. All other cells investigated, i.e., B-lymphocytes (To15+), B-accessory cells (Ki-M4+), natural killer cells (Leu-7+), eosinophils, and tissue mast cells were usually encountered only in very small numbers of were virtually absent from the lymphoreticular infiltrates. A comparison of the cellular reaction in the primary tumors and their corresponding cervical lymph node metastases revealed differences for T8-lymphocytes, T4-cells, and T-accessory cells. Although T8-lymphocytes were more numerous in both the stroma and tumor foci of the metastases than in the primary tumors, T4-cells and T-accessory cells were present in greater numbers only in the tumor foci of the metastases. The preferential localization of tumor-infiltrating lymphoreticular cells in the tumor stroma and the absence of a visible cytotoxic effect of lymphocytes and macrophages in direct contact with tumor cells support the hypothesis of a deficient immune response to clinically detectable squamous cell carcinomas of the head and neck region.