Melan-A

Melan-A (also known as Mart-1) is a protein made by certain types of cells in the body. It is most commonly found in melanocytes, which produce melanin, a pigment that gives colour to skin, hair, and eyes. Melan-A is also important in pathology because it can help pathologists identify specific types of tumours.

What is the function of Melan-A?

Melan-A plays a role in the normal development and function of melanocytes. It is involved in producing melanin, the pigment that protects the skin from harmful ultraviolet (UV) radiation. Melan-A is also a useful marker for identifying tumours arising from melanocytes or cells that behave like them.

What types of normal cells and tissues express Melan-A?

Melan-A is normally expressed by melanocytes, the pigment-producing cells in the skin, hair, and eyes. It is also found in a specific part of the adrenal glands called the zona reticularis. These are normal, non-cancerous cells that use Melan-A in their regular functions.

How do pathologists test for Melan-A?

Pathologists test for Melan-A using immunohistochemistry. This test uses special antibodies that attach to Melan-A if it is present in the cells being examined. When the antibody attaches, it causes a colour change that can be seen under a microscope. The test helps pathologists determine if a tumour is made up of melanocytes or similar cells. This information is included in the pathology report and helps doctors make a diagnosis.

What types of benign tumours express Melan-A?

Benign (non-cancerous) tumours that express Melan-A include:

• Nevus: Commonly known as a mole, a nevus is a benign tumour of melanocytes.
• Adrenal cortical adenoma: A benign tumour that develops in the adrenal gland.
• Angiomyolipoma: A benign kidney tumour that contains blood vessels, smooth muscle, and fat cells.
• PEComa (perivascular epithelioid cell tumour): A rare benign tumour that can develop in different parts of the body and often expresses Melan-A.
• Melanotic schwannoma: A rare benign tumour that arises from nerve sheath cells and has pigment-producing capabilities.

These tumours are usually non-cancerous, but testing for Melan-A helps confirm their origin and rule out more serious conditions.

What types of malignant tumours express Melan-A?

Malignant (cancerous) tumours that express Melan-A include:

• Melanoma: A type of cancer that starts in melanocytes. Melan-A is frequently used to confirm this diagnosis.
• TFEB renal cell carcinoma: A rare type of kidney cancer associated with genetic changes involving the TFEB gene. This tumour can express Melan-A, which helps pathologists identify it.
• Clear cell sarcoma: A rare cancer that typically develops in soft tissues and behaves similarly to melanoma.

Testing for Melan-A in these tumours provides valuable information to guide diagnosis and treatment.