Desmin

Desmin is a 52 kDa cytoplasmic intermediate filament protein normally found in muscle cells, including smooth, skeletal, and cardiac muscle. It is encoded by the DES gene and helps maintain the structural integrity and contractile function of muscle fibers. In immunohistochemistry, desmin shows cytoplasmic staining, sometimes with perinuclear dot‑like positivity in certain tumours. Desmin is used as a screening marker for myogenic differentiation, as it is typically positive in tumours such as rhabdomyosarcoma, rhabdomyoma, leiomyosarcoma, leiomyoma, and other lesions with smooth or skeletal muscle components. It is also variably expressed in some myofibroblastic and genital stromal tumours, making it a helpful part of broader diagnostic panels (1-2).

Recommended Controls

Criteria for acceptable staining is a cytoplasmic staining pattern. The recommended controls to include is appendix, tonsil and normal bowel. Appendix as a negative and positive control: all the muscle cells must show a strong cytoplasmic staining reaction, moderate staining in the smooth muscle cells and no staining should be seen in the epithelial cells. The tonsil as a negative where the lymphocytes and epithelial cells will be negative. Normal bowel should be strongly positive in the muscular wall.

Expected staining pattern

Appendix

Tonsil

Duodenum mucosa

Muscle

Disclaimer

These methods are intended as a guide only. Laboratories that wish to implement these methods should perform internal validation/verification prior to use. The RCPAQAP does not make any claim or warranty for the accuracy or performance of these methods.