NEW YORK (Reuters) - Actress Valerie Harper best known as wise-cracking neighbor Rhoda Morgenstern on television's "The Mary Tyler Moore Show," has been diagnosed with terminal brain cancer, People magazine reported on Wednesday.

Doctors told Harper, 73, on January 15 that she had as little as three months left to live after a battery of tests revealed she has leptomeningeal carcinomatosis, according to People. The rare condition occurs when cancer cells spread into the fluid-filled membrane surrounding the brain.

Harper previously battled lung cancer in 2009 and discussed that challenge in her new memoir "I, Rhoda."

Aside from playing Moore's neighbor on the 1970s TV sitcom, Harper is best known as the star of her own TV series "Rhoda" and her Tony-nominated portrayal of Broadway legend Tallulah Bankhead in the play "Looped."

(Editing by Barbara Goldberg and Jeffrey Benkoe)