Janet Marylyn Frager passed away on Tuesday (12Jul16), aged 84, and the Cast Away star took to Instagram.com to share a sweet tribute to his mum, a former hospital worker.

The actor, who marked his age milestone on Saturday (09Jul16), posted a black-and-white photo of a young Janet, and in the caption, he wrote, "This beauty? My mom. She was the difference in many lives. Many lives.

"We say goodbye to her today. Safe crossing, mom!"

Tom's wife, actress/singer Rita Wilson, also took to social media to remember her late mother-in-law with a snap of Janet and her famous son.

"This wonderful lady gave birth to my husband, and three other children. Thank you for bringing my love into the world," Rita wrote. "She is at peace now."

A cause of death has yet to be announced.

Janet was married to Amos Mefford Hanks and the California-based couple had four kids - Tom, Sandra, Larry, and actor/filmmaker Jim. They divorced when Tom was five, splitting up the family as Jim remained with his mother, while his older siblings lived with their dad.

Tom recently opened up about his youth during an appearance on BBC Radio 4's Desert Island Discs show in May (16), when he described the loneliness of his childhood as he explained his music choices.

Asked why he selected Strauss' Also Sprach Zarathustra, the theme to 2001: A Space Odyssey, he revealed that the music impacted him as a teenager, after a nomadic childhood with his chef father Amos, living in 10 houses in five years.

"This was the 'wow' moment of my life going from kid trying to figure out what's interesting in this life to young man yearning to be an artist," he told host Kirsty Young. "I started asking myself... how do I find the vocabulary for what's rattling around in my head?

"Not long after I started going to the American Conservatory Theatre by myself to see plays I had no idea even existed."

When asked what the thoughts "rattling around" in his head were, Tom became audibly emotional, and wiped tears from his eyes: "I put too much thought into this list," he continued. "What it was, it was the vocabulary of loneliness."