The presence of malignant cells within CNS evokes immunological response, manifested morphologically as infiltrations composed of lymphocytes and macrophages. Studying of intensity of these infiltrations may potentially have prognostic value and help to choose patients for future immunotherapy. The aim of the study was to assess quantitatively lymphocytic infiltrations within metastatic tumours of the brain taking into account contribution of T and B cell populations. 48 brain metastases obtained intraoperatively during craniotomy were examined. T-cells and B-cells were identified immunohistochemically on paraffin sections with monoclonal antibodies anti-CD45RO and anti-CD20-Cy, respectively. Afterwards they were counted in 35 randomly selected fields of vision in each specimen. T cells were observed in all 48 brain metastases, B-cells in 39 of them. The mean number of T and B cells seen in a field of a microscope was 3.12 and 0.83. The mean T/B ratio was 7.2. A high positive correlation of intensity of T and B cell infiltrations was found (r=0.45). The lymphocytes were especially abundant in perivascular spaces and in connective tissue tumour stroma. It is concluded that T lymphocytes predominate in lymphocytic infiltrations in brain metastases. A high T/B correlation indicates synchronous activation of cellular and humoral response against the presence of metastatic cancer cells in the brain.

Keywords: tumour stroma, lymphocytic infiltrations, brain metastases, Neoplasms