actually it isn't an uncommon symptom of brain tumor. my father had phantom smells. Phantom smells can be a symptom of simple partial seizures. these seizures originate in the temporal lobe. So for people with tumors in the temporal lobe, this is common. He always smelled nail polish or nail polish remover. to this day if I smell that, I look or start asking who painted their nails.
NOW having said that sinus issues can do it as well. AS can nothing sinister at all. My sister in law is always smelling stuff that isn't there. Anxiety/Stress can too.. this is especially true when one is afraid of phantom smells.
I know I get them sometimes. a few years back I was getting them pretty often. At the time there were a lot of stressors going on in my life. and with my dad's BT history, it made it worse for me. You will find many posts here at AZ about phantom smells.
So while my dad did have a temporal lobe tumor and phantom smells, he also had slurred speech, inability to use his left arm and leg AND complete loss of peripheral vision in his right eye. Not comes and goes, but complete 24/7 loss.
Brain tumors are a common fear around here. in the 5+ yrs I've been a member, only one person has been dx'd with a tumor--benign menigioma. It was found incidentally on an MRI. It wasn't even big enough to cause symptoms. docs only remove those if they start impeding brain function. My sister had a HUGE menigioma removed in 2008. Hers was DEFINITELY impeding brain function. She had motor focal seizures but didn't have phantom smells. Her tumor was on her frontal lobe. she is, btw, doing fine now
So you may well be having phantom smells but that is in NO way a determining symptom of bt.
do something good for yourself today. Your mind/body will thank you for it.