<s>[INST] Hello I have a lump on the top of my arm pit. I squeeze it and I can feel the pus just pushing out of it. Sometimes it s just long and stringy and is white. Other times it looks like a darker pus (kinda brown). I have it now and this is my third time getting it. The pus don t smell. The bump gets to be about a little smaller than a marble and i can grab with my fingers. What do you think may cause this? I m starting to worry about it now. Is it something I should have checked out? [/INST] Hi. The site and size of the lump tells me about the possibility of infected sebaceous cyst in armpit, a common site for this problem.I would advise to get this checked out and request the Doctor to get this excised as this will be a constant site for non-healing. </s>