Tumor immune microenvironment has been gradually recognized as a key contributor to
tumor development, progression, and control. Immune cell infiltrates in
brain tumors have been increasingly studied, but few have published on immune cell infiltrates in
pituitary adenomas. We quantitatively assessed the infiltration of macrophages and lymphocytes in 35
pituitary adenomas, including 9 densely granulated
growth hormone (DG-GH), 9 sparsely granulated
growth hormone (SG-GH), 9 null cell (NC), and 8
adrenocorticotropic hormone (
ACTH)
adenomas. All the
adenomas showed varying degrees of CD68+ macrophage infiltration. While SG-GH
adenomas were significantly larger in size than DG-GH and
ACTH adenomas, the infiltration of CD68+ macrophages was significantly greater in SG-GH than in DG-GH and
ACTH adenomas. Similarly, NC
adenomas that were significantly larger than DG-GH and
ACTH adenomas had significantly greater infiltration of CD68+ macrophages than DG-GH and
ACTH adenomas. The numbers of CD68+ macrophages were positively correlated with the
tumor sizes and Knosp classification grades for
tumor invasiveness. The infiltration of CD4+ and CD8+ T cells was relatively scant in these
adenomas, but GH
adenomas exhibited significantly more CD4+ and CD8+ T cells than non-GH
adenomas. Both DG-GH and SG-GH
adenomas had significantly more CD4+ cells than
ACTH adenomas and significantly more CD8+ cells than NC
adenomas. These results suggest an association of CD68+ macrophage infiltration with an increase in the
pituitary adenoma size and invasiveness. Our observation contributes to understanding the growth environment of
pituitary adenomas, for which adjuvant
immunotherapy may help to constrain the
tumor enlargement and invasiveness.