 [ Symptoms ] how effective is the seasonal flu vaccination [ Disease ] most helpful answer thanks for providing all the great background information if several different doctors have told you the blemish is a cyst then that is probably accurate a cyst is a pocket of tissue that is filled with some type of fluid the type of fluid can vary depending on the type of cyst some are filled with fatty acids while others contain pus it sounds like your cyst is located within the skin layer not in the breast tissue which is good news skin cysts are very common and do tend to drain occasionally as you have described the fact the cyst has gotten bigger and changed color is a good reason to have a health care provider re evaluate this it is possible the cyst needs to be treated by having it drained or even removed only your health care provider can say for sure cysts are an annoyance but luckily they are not a serious disease good luck to you as you cope with this