cysts on toddler's knee

hi,

My son is currently taking antibiotics for an infected cyst (about the size of a sugar cube) on the front of his knee. This cyst burst last week and produced a large amount of yellow pus and blood. It is very visible still but does look less angry.  At the same time I noticed another pea-sized growth on his knee which remains under the skin and is uninfected but has increased in size in the last few days.  I am concerned as to what is causing these cysts and whether I should worry about cancer or anything else.  He is 18 months and otherwise seems healthy.

Thanks,

Cath

[Alan Rockoff, MD]

You should not worry about cancer.  Cysts are common at any age, and they are not related to cancer in any way.  I don't know why your son has two--I don't even know for sure that the second one is a cyst.  It may be another sort of under-the-skin bump (also noncancerous!)  I advise you to leave it alone and show them to his doctor and not worry.

Take care.

Dr. Rockoff