Dusty Roads is a 4-year-old cocker spaniel who came to see us for his annual physical exam and vaccines. Dusty's owners noticed that he had a large lump right over his trachea(wind pipe) that seemed to be growing slowly over time. He didn't seem bothered by it, but we were concerned by the growth so we decided to take a sample of cells out with a needle.

Dusty
(select to enlarge)

Under the microscope it appeared that we had a lot of sebaceous material that is usually secreted by hair follicles, so logically we thought that Dusty had a sebaceous cyst forming within his skin. In order to get better drainage, we shaved the fur on his neck and numbed the surface of Dusty's skin. We then lanced the area to try and drain the cyst.

What we actually found really surprised us! When we opened the skin, we DID get a lot of sebaceous material, but we also found a large amount of hair growing WITHIN Dusty's skin. Because he is a Cocker spaniel, and his fur just keeps growing, the mass was getting larger as the fur got longer and longer!

Dusty's cyst (select to enlarge)

This condition is called a dermoid sinus which results from a defect in embryonic development resulting in incomplete separation between the skin and the neural tube. A sinus forms from the skin and ends in a blind sac in the fat underneath the skin, or could even go back all the way to the spinal cord. Surgical removal is necessary to prevent further growth as well as reoccurrence, but it is a benign lesion.

. In Dusty's case, we cleaned out the sinus as best as possible and trimmed back the hair that was found there. Eventually skin will close over the opening and the mass will again get larger as the fur grows longer. The owners are considering surgical removal.

Dusty's cyst (select to enlarge)

Dusty's cyst (select to enlarge)