CD68

CD68 is a protein normally found on the surface of macrophages, a type of immune cell, and cells related to macrophages. Macrophages help protect your body by engulfing and removing bacteria, damaged cells, and other particles. CD68 helps macrophages carry out their role in the immune response.

Why do pathologists test for CD68?

Pathologists test for CD68 to determine whether macrophages are present in a tissue sample. Identifying macrophages can help pathologists diagnose conditions that involve inflammation, infections, or tumours originating from or containing large numbers of macrophages.

How do pathologists test for CD68?

Pathologists use a test called immunohistochemistry to look for CD68 in tissue samples. During this test, special antibodies designed to recognize the CD68 protein are applied to a thin piece of tissue placed on a microscope slide. If CD68 is present, the antibodies bind to the cells, causing a colour change. Cells showing this colour change are called “positive,” meaning they contain CD68, while those without the colour change are called “negative.”

What types of normal cells and tissues will be positive for CD68?

Normal cells positive for CD68 include:

• Macrophages: Immune cells found throughout the body, including tissues such as lymph nodes, bone marrow, liver, spleen, and skin.

• Histiocytes: Histiocytes are a type of macrophage located in tissues.

These cells naturally express CD68 as part of their role in the immune system.

What types of tumours will be positive for CD68?

Tumours and tumour-like conditions positive for CD68 include:

• Histiocytic tumours, such as histiocytic sarcoma, which originate from macrophages.

• Fibrous histiocytoma, a common benign (noncancerous) tumour found in the skin.

• Giant cell tumour of tendon sheath and giant cell tumour of bone, tumours that typically contain many CD68-positive macrophage-like cells.

• Certain types of lymphoma or leukemia when macrophages are present within or around the tumour cells.

Identifying CD68 in these tumours helps pathologists confirm the diagnosis, distinguish these tumours from other similar-looking conditions, and supports accurate treatment decisions.