<s>[INST] I think I have a cyst and Im very scared. Its very swollen and pops frequently with puss and blood. My biggest fear is that its gone into my leg, as it hurts, I can hardly walk and a particular long vein on my left has is popping out and is red, not the typical green my veins usually are. Please help!!!! [/INST] Thanks for posting you query to Chat Doctor .cyst are fluid filled sac and formed below layer of skin or in the internal organ. Usually they produce symptom depend upon compressive effect on neighboring organ. Cyst are filled with blood or pus only when they become secondarily infected .if you are having any pulsatile swelling it will not be cyst but something else.treatment of cyst is surgical removal, so you should contact to General Surgeon for local examination and then take treatment accordingly. Hope you would be satisfied with my answer.  Feel free to communicate if any query.regards, Chat Doctor.  </s>