Pathology dictionary -


Desmin is a protein made by muscle cells. It is produced by both normal muscle cells and tumours made out of muscle.


There are three different kinds of muscle cells in our body:

  1. Cardiac muscle cells – These are the cells that make up the heart.

  2. Skeletal muscle cells – These are the cells that make up most of the muscles in our body. Skeletal muscle cells can be very large (like the ones in our legs) or very small (like the ones that move our eyes). We control these muscles and they allow us to walk, run, talk, and breathe.

  3. Smooth muscle cells – These muscle cells are found inside our blood vessels and internal organs. Smooth muscle cells help move food along our gastrointestinal tract and open and close our blood vessels to change our blood pressure.

All three types of muscle cells produce desmin. Tumours made up of muscle cells also produce desmin. These kinds of tumours can be non-cancerous (benign) or cancerous (malignant). Most cancers made from muscle cells are called sarcomas.

Desmin can also be produced by a cell that was not originally a muscle cell but has started to look and behave like a muscle cell. In this case the cell will usually also produce proteins that not normally made by muscle cells.

How do pathologists test for desmin?

Pathologists perform a test called immunohistochemistry to look for cells producing desmin. This test helps your pathologist decide if the tumour is made up of muscle cells or if the cells are starting to behave like muscle cells. 

If the cells in your sample produce desmin, your report will describe the cells as positive or reactive. If they do not produce desmin, your report will describe the cells as negative or non-reactive.

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