Immune Cell Infiltration in Feline Meningioma.

Area of Science:

• Veterinary Pathology
• Immunology
• Oncology

Background:

• Meningioma is the most common primary brain tumor in cats.
• While often histologically benign, the tumor microenvironment, particularly immune cell infiltrate, is poorly understood in felines.
• Previous studies characterized immune cells in human and canine meningiomas, highlighting a knowledge gap in feline equivalents.

Purpose of the Study:

• To characterize the immune cell infiltrate in feline meningioma.
• To investigate the presence and types of immune cells within feline meningioma tissue.
• To establish a baseline for understanding the immune microenvironment's role in feline meningioma.

Main Methods:

• Seventeen feline meningioma samples were analyzed using light microscopy and immunohistochemistry (IHC).
• Specific markers were used to identify T lymphocytes (CD3), B lymphocytes (Pax5), and macrophages (Iba-1, HLA-DR, MAC387, CD163).
• Cell proliferation was assessed using Ki67 staining, and correlations between cell types were explored.

Main Results:

• All feline meningiomas showed variable immune cell infiltrates.
• Moderate CD3+ T lymphocytes and abundant Iba-1+ and HLA-DR+ macrophages were consistently observed.
• Significant infiltration of MAC387+ (88%) and CD163+ (76%) macrophages was noted, with considerable variation.
• Pax5+ B lymphocytes were present in 41% of cases.
• A weak negative correlation was found between CD3+ and Ki67+ cells (P=0.018).

Conclusions:

• Feline meningiomas possess a robust immune cell infiltrate, comprising T lymphocytes, B lymphocytes, and diverse macrophage populations.
• The findings confirm the presence of a complex immune microenvironment within feline meningiomas.
• Further investigation is warranted to elucidate the functional role of these immune cells in tumor progression and patient outcomes.