Lump in thigh area

Hello about a few months ago I develoved what I thought was a ingrown pimple in my thight. About 6" below groin area and on my inseam.   It slowly grew to the size of a large marble. Then in time it shrank to almost a pin head. It has repeatd this 3 times  Everytime it is almost gone  it comes back and gets big again.;  My GP said its probably a cist. Not to worry about it..    But why does it keep almost go away then come back so large. the skin around it apears bruised could this be a cancer or a STD? there is no puss or opening in the skin.  Hoping you have advise.  

[Bhupinder Kaur, MD]

Hello,
From the symptoms it can be an infected hair follicle, cyst or some benign skin growth. From the increase and decrease in size, chances are more likely that it is a cyst. Blocked sebaceous glands, swollen hair follicles and excessive testosterone production will cause such cysts.

Generally no treatment is required but they become painful then it means they are infected, then surgical excision by traditional wide excision, minimal excision, and punch biopsy excision may be required.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.