tumor infiltrating lymphocytes
Immune cells present within tumor tissue, indicating host immune response activation.
Full Definition
Tumor infiltrating lymphocytes (TILs) are immune effector cells that have migrated from the bloodstream into tumor tissue, representing the body's attempt to mount an anti-tumor immune response. TILs include various immune cell populations such as CD8+ cytotoxic T cells, CD4+ helper T cells, natural killer cells, and B cells. The presence, density, and composition of TILs have emerged as important prognostic and predictive biomarkers in various cancers, particularly breast cancer, melanoma, and colorectal cancer. High TIL infiltration generally correlates with better prognosis and increased likelihood of response to immunotherapy. TILs can be assessed through histopathologic evaluation or advanced imaging techniques.
Usage
Usage note: Distinguish location - intratumoral vs. peritumoral TILs have different prognostic significance.
In Context
- "High levels of tumor infiltrating lymphocytes predicted excellent response to checkpoint inhibition." — immunotherapy consultation
- "Pathologic assessment revealed dense tumor infiltrating lymphocytes throughout the specimen." — pathology report