The Pathology Dictionary Team
February 15, 2023

What is Melan-A?

Melan-A (also known as MART-1) is a protein primarily expressed in cells called melanocytes. These pigment-producing cells give color to the skin, hair, and eyes. Melan-A is often used as a marker to identify and diagnose melanoma, a type of cancer that arises from melanocytes.

What is Melan-A used for in pathology?

Melan-A is used primarily for the diagnosis and classification of melanoma. In this context, it is used to distinguish melanoma from other types of cancer or noncancerous conditions that may look similar to melanoma under the microscope. However, it’s important to note that Melan-A expression is not specific to melanoma and can also be found in tumours of the adrenal gland, some types of lymphoma (such as anaplastic large-cell lymphoma), and some types of sarcoma (such as clear cell sarcoma). For this reason, the expression of Melan-A must be considered in conjunction with other test results before reaching a final diagnosis.

How do pathologists test for Melan-A?

Pathologists perform a test called immunohistochemistry to look for cells producing Melan-A. The test is performed on a tissue sample such as a biopsy.

This image shows melanocytes that are positive for Melan-A by immunohistochemistry. The Melan-A-expressing cells are brown.

What does positive for Melan-A mean?

Positive means that the cells in the tissue sample express Melan-A.

What does negative for Melan-A mean?

Negative means that the cells in the tissue sample do not express Melan-A.

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