A sebaceous cyst is a small sac containing an accumulation of secretions produced by the sebaceous glands. Sebaceous cysts are also known as epidermoid cysts, epidermal inclusion cysts, epidermal cysts, and wens.
The sebaceous glands produce an oily substance called sebum, which lubricates the skin. The ducts of the sebaceous glands empty into hair follicles. The development of sebaceous cysts is thought to arise from an obstruction of the follicles, leading to abnormal accumulations of sebum.
Sebaceous cysts are common in dogs. They are commonly seen in schnauzers and cocker spaniels, although any breed can develop them. Often if one is found, more will develop as the dog ages. There is no significant impact on your pet, as these are benign growths. Occasionally, the cysts may get infected or inflamed, causing you pet to lick or bite at them.
What to Watch For
- Smooth, round firm to fluctuant growths, roughly 5mm to 5cm in diameter. They may have a slightly blue color to them.
- Release of a grayish white or brown discharge with a cheesy consistency.
- Development of cysts on the head, neck, body and upper legs.
- Fine needle aspiration. A diagnosis can often be made by placing a small needle within the cyst and suctioning some cells out of it with a syringe. Microscopic evaluation of the cells will often be suggestive of a sebaceous cyst.
- Biopsy. A definitive diagnosis may require a sample of tissue that has been surgically removed.
In most cases no treatment is necessary. If the cyst becomes inflamed or infected, keep the area clean until your veterinarian can advise you on treatment if necessary. If the decision is made to biopsy the cyst, complete surgical removal is usually performed. This is curative.
At home, monitor the cyst for changes in size or evidence of irritation. Although these are benign growths, fine needle aspiration does not always provide a conclusive diagnosis. For this reason, rapidly enlarging masses should be surgically removed and biopsied to ensure there is no evidence of malignancy (cancer).