Thank you for your question. Any time that you have a new or growing lump on your arms, it is something that you should discuss with your doctor
to see if it is something serious that you need to worry
about. There are many different explanations, but it is hard to say more without knowing more about your overall medical health. Skin discolorations can happen for many reasons as well, and it is interesting that you have had this discoloration for as long as you can remember. There are some medical conditions that could present as a discoloration and then proceed to involve the local area of the body with additional lumps as the condition spreads, but most of these are somewhat rare and unusual. In most cases, it is more likely to have a normal explanation that helps to link all of the symptoms that you are having. Speaking with your doctor will provide the information and testing that you may need to get the answers to your questions. Again, please speak with your doctor about this problem.