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The lump is producing pressure symptoms now and hence should probably be removed. It can be a cyst or a swollen lymph node or a lipoma or a neurofibroma (collection of nervous and fibrous tissue). Though not as such a cause of concern, any lump increasing in size and causing symptoms, should be properly investigated. TAKE A SECOND OPINION.
Seems to me you're asking the right questions but your doctors do not seem to be listening to your concerns.
My suggestion, SWITCH DOCTORS, and keep doing that until you find the one who WILL LISTEN.
YOU are your best advocate when it comes to your body and your health.
Do not EVER let a doctor's lack of interest in your health concerns dictate that it's simply not important enough an issue to address.
If YOU ARE CONCERNED ABOUT IT, find a doctor who cares enough to acknowledge that!