Loni Anderson's Cause of Death Revealed

Loni Anderson’s cause of death has been revealed ... and she died from an aggressive form of cancer, TMZ has learned.

According to Anderson's death certificate, obtained by TMZ, the veteran actress passed away from metastatic uterine leiomyosarcoma ... a rare cancer that often starts in the uterus and can spread to other parts of the body. It is an extremely rare form of cancer.

Loni died Sunday at a Los Angeles hospital following what her longtime publicist, Cheryl J. Kagan, described as a "prolonged" illness.

The iconic actress was best known for playing Jennifer Marlowe on "WKRP in Cincinnati" -- the beloved sitcom about a struggling Ohio radio station that aired in the late '70s and early '80s.

Loni’s personal life also made headlines -- especially her high-profile marriage to Burt Reynolds. The two tied the knot after costarring in the '83 comedy “Stroker Ace,” but split five years later.

She was 79.