Tumor infiltration by immune cells: Pathologic evaluation and a clinical significance

Abstract

Tumor infiltrating leukocytes comprise a significant population of cells in the tumor microenvironment. Pathologic evaluation of tumors by methods of light microscopy and immunohistochemistry allow identification of all types of leukocytes, including the cells of myeloid, monocytoid and lymphoid origin. The density of these cells, their spatial distribution in tumor islets and stroma, their level of maturation and functional status vary considerably in the tumors of different nature, grade and stage. By the analysis of clinical data it has been shown that specific types of tumor infiltrating leukocytes have a major impact on the clinical course and the outcome of malignant diseases. This chapter describes an approach used by pathologists to gain insight into morphologic and functional properties of tumor infiltrating leukocytes, as well as their prognostic significance.