Hi,Welcome to HCM.
Based on the facts of your query,as the lump on your back was painless and existing before anti-retroviral treatment,as confirmed from your partner and as it doesn't move,it seems to be either-a Lipoma or a Sebaceous Cyst on the back.
Second opinion from your treating doctor and
Dermatologist would rule out any anti-retroviral induced
Lipodystrophy causing fat lumps due to fat redistribution.
So don't worry it.Consult your HIV treatment doctor, who would treat this lump with all the care it needs.
Second opinion from Surgeon and FNAC
Biopsy with histo pathological study of the back lump after the USG of the lump to rule out Sebaceous Cyst,would resolve your worries.
This reply would resolve your current issues and would reduce your
anxiety with it.
Hope this reply would help you to plan treatment with your doctor.
Will appreciate your Hitting thanks and writing excellent review comments to help needy patients like you.
Welcome with any other further query in this regard.
Good Day!!
Dr.Savaskar,
Senior Surgical Specialist
M.S.Genl-CVTS