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Giant Comedo

Author: Nadia Vryoni

Chief Editor: Dr Daniel Keith

A giant comedo is a large open comedone (black head), formed when the sebaceous duct/follicle becomes blocked by debris such as bacteria or oil. They are most commonly located on areas rich in sebaceous glands, like the chest, face and back. However, they can arise on most parts of the body. Anyone can develop a giant comedo, but they are more common in individuals with a history of acne.
 

Macroscopic appearance

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A giant comdeo can range from a few mm up to 2cm and appears as a bump under the skin with the open comedone clearly visible underneath.

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This is the macroscopic appearance after it's contents have been expressed.

Dermoscopic appearance

Under dermosccopy the wall of the sebaceous cyst/follicle will be visibly dilated around the keratinous content which plugs the follicle.

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Annotated example of the same giant comedo illustrating:

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  • Left arrow: Keratinous contents/plugging or ruptured opening(s)

  • Right arrow: Thin wall of filated cyst/follicle

Unannotated example for comparison.

Dermoscopic view of this giant comedo after it's contents had been expressed.

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