Are Olfactory Hallucinations SYMPTOMS of a brain tumor ?

an aunt of mine can smell petrol fumes where ever she is. my brother could as well before his brain tumor was detected. the surgeon told my brother that this was a classic symptom of a brain tumor. but in my aunts case no one has ever heard of this. my brothers doctors did not act when he told them about the smell. has anyone else heard of this in relation to brain tumors? for my aunts sake.