Melanoma tumour infiltrating lymphocytes, light micrograph. Tumour infiltrating lymphocytes (TIL) in melanoma convey important prognostic information. A dense lymphocytic infiltrate within and around melanoma appears to correlate with better prognosis. The lymphocytic response is subdivided into three categories; brisk, non-brisk, or absent. Brisk: TILs are present throughout the vertical growth phase or across the entire base of the tumour. Non-brisk: TILs focally infiltrate the tumour. Absent: TILs are absent altogether OR they are present but do not infiltrate the tumour. This light photomicrograph shows non-brisk response. Lymphocytes are seen focally infiltrating melanoma cells on the lower left corner of the image.