1 lump on right forearm, 2 lumps on left forearm

My husband is 29 years old and for the past several years he has had 1 lump on his right forearm (right below elbow) and 2 on his left arm (1 next to wrist and one in upper forearm).  He went to the dermatologist and had her look at it -- she said it was a lymph node but wasn't sure.  Then another dermatologist came into the room and said she did not think it was a lymph node.  They had no clue, so they ordered an ultrasound.

The ultrasound revealed that all 3 lumps were superficial and not lymph nodes, but they also were not lipomas.  The doctor now wants to schedule a biopsy, and says it could be "muscle-related" and they didn't know what they were.  What could this be that is muscle-related?  Could it still be a lipoma or cyst?  What else could it be?  It's just frustrating to go into a biopsy and not be told the possibilities -- like, I've had biopsies before and the doctor tells me "it's either a mole or melanoma" or "it's a breast cyst or breast cancer."  You know what I mean?  Any thoughts would be great.