Oh, I had forgotten about this one: The Manitou. It's an odd ball.
Plot
A woman named Karen (Susan Strasberg), who is suffering from a growing
tumor on her neck, enters a hospital in
San Francisco. After a series of
X-rays, the doctors begin to think it is a living creature: a
fetus being born inside the tumor. Eerie and grisly occurrences begin; the tumorous growth perceives itself – himself – to be under attack as a result of the X-rays used to ascertain its nature, which are starting to stunt and deform its development. The growth is the old Native American
shaman,
Misquamacus; he is reincarnating himself through the young woman to exact his revenge on white men who invaded North America and exterminated its native peoples. Karen's boyfriend, psychic fortune-teller Harry Erskine (
Tony Curtis) contacts a second Native American shaman (
Michael Ansara) to help fight the reincarnating medicine man, but the kind of spirits he can summon and control appear to be too weak to match his opponent's abilities.
https://en.wikipedia.org/wiki/The_Manitou