Tumor-infiltrating lymphocytes

Tumor-infiltrating lymphocytes, also tumour infiltrating lymphocytes, are white blood cells that have left the bloodstream and migrated into a tumor. They are usually abbreviated TILs. When numerous, TILs are considered to be prognostically significant.

Colorectal cancer
In colorectal cancer, they are associated with microsatellite instability cancers, as may be seen in Lynch syndrome.

When TILs are present the lymphocytes are found between the tumor cells; cells in the stroma surrounding the tumor cells do not count. It should be noted that histologic definitions for TILs vary.

Melanoma
They are an important prognostic factor in melanoma and higher levels being associated with a better outcome.

They are key to an experimental autologous cell therapy (Contego) for metastatic melanoma. Several centres are currently working on TIL melanoma treatment protocol, including the Ella Institute in Sheba Hospital, Israel and Copenhagen University Hospital at Herlev, Denmark