growth under skin

About two years ago, I felt a small lump under the skin of my right upper arm.  It is slowly growing and is blue.  My doctor (general practitioner) says it is an epidermal inclusion cyst but nothing I can find on internet confirms this.  Now my right arm is getting noticeably smaller than my left arm.  Lump does not protrude and is not sore but the blue color is obvious to the naked eye.  If my R arm was not getting smaller, I would not think too much of it.  I'm 65 yrs. old.

[Alan Rockoff, MD]

Cysts can sometimes appear dusky, so it's possible.  I can't make any sense of your observation that the right arm is "getting smaller"--I can't think of any growth of any kind that would contribute to that.  My advice is to see a dermatologist for another opinion, and then go from there.

Best.

Dr. Rockoff

[janpoo]

I first noticed my right arm getting smaller when a fitted sleeve above my elbow was loose on my right arm and tight on my left.  I switched sleeves and got same results.  The fleshy part of my R arm is smaller than Left.  I have a touch of arthritis in my R shoulder and wonder if I have favored the R arm and am losing flesh/muscle.