Tumor-infiltrating lymphocytes: Cytologic, Phenotypic and morphometric analysis

OBJECTIVE: To characterize the cytologic, phenotypic and morphometric features of tumor-infiltrating lymphocytes (TILs). STUDY DESIGN: Morphology and cell size parameters of 50 TILs and five normal donor peripheral blood lymphocyte (PBL) specimens were compared using light microscopy, manual ocular measurements and digital image processing. RESULTS: Cytologically, all TILs demonstrated similar morphologic findings regardless of the initial tumor type. Changes included large, eccentric nuclei, sometimes hyperlobated; clumped chromatin; and prominent nucleoli. The cytoplasm was abundant and basophilic. Mitotic figures were usually evident. In addition, TIL showed significant increases in cell size parameters as compared to PBLs. CONCLUSION: The activated morphology of TILs resembles the appearance of high grade lymphoma. Several cell size parameters are increased; that may help to explain differences in previously reported trafficking patterns between TILs and peripheral blood lymphocytes.