Tumor-infiltrating lymphocytes expressing IOT-10 marker. An immunohistochemical study of a series of 185 brain tumors.

The presence of IOT-10-positive lymphocytes among the tumor-infiltrating-lymphocyte (TIL) population was studied in a series of 185 brain tumors. In most of the tumors, IOT-10-positive lymphocytes were identified, but generally they were scarce and masked among the tumor cells, suggesting that NK-cells exercise a poor participation in the tissular response against brain tumors. Isolated tumor cells showing IOT-10-positivity were found in low-grade astrocytomas, neurinomas and medulloblastomas. IOT-10-positivity on both tumor neuropil and tumor cells was considered a characteristic finding in oligodendrogliomas. The number of IOT-10-positive NK-cells in brain metastases and in cerebellar hemangioblastomas was comparatively greater than in other types of brain tumor. Since in brain metastases, the presence of IOT-10-positive NK-cells can be related to the tissular response to an extracerebral malignancy, their considerable presence in cerebellar hemangioblastomas is an enigmatic finding that deserves further attention.