There's a lot to unpack in a new piece titled "30 Things I Learned Before Turning 30" that Taylor Swift -- who celebrates the milestone birthday in December -- just wrote for ELLE magazine.

Cooper Neill / Getty Images for dcp / .

But buried at No. 24 is a sad new revelation: Her mother Andrea's cancer has returned. "I've had to learn how to handle serious illness in my family," Taylor writes. "Both of my parents have had cancer, and my mom is now fighting her battle with it again."

Andrea was first diagnosed with the disease in 2015, though the Swifts have never revealed what type of cancer the former mutual fund marketing executive had.

Taylor had also not previously disclosed that stockbroker dad Scott had battled the disease.

Getty Images

"It's taught me that there are real problems and then there's everything else," Taylor continued in her piece for ELLE. "My mom's cancer is a real problem. I used to be so anxious about daily ups and downs. I give all of my worry, stress, and prayers to real problems now."

The pop superstar took to Tumblr nearly four years ago to tell fans about Andrea's first cancer diagnosis. "I'm writing to you with an update I wish I wasn't giving you, but it's important and I'm used to sharing important events in my life with you. Usually when things happen to me, I process them and then write music about how I feel, and you hear it much later. This is something my family and I thought you should know about now," she wrote.

Jim Smeal/BEI/REX/Shutterstock

"For Christmas this year, I asked my mom that one of her gifts to me be her going to the doctor to get screened for any health issues, just to ease some worries of mine. She agreed, and went in to get checked. There were no red flags and she felt perfectly fine, but she did it just to get me and my brother off her case about it," she continued. "The results came in, and I'm saddened to tell you that my mom has been diagnosed with cancer. I'd like to keep the details of her condition and treatment plans private, but she wanted you to know."

Taylor went on to explain why she was making news of Andrea's health crisis public: "She wanted you to know because your parents may be too busy juggling everything they've got going on to go to the doctor, and maybe you reminding them to go get checked for cancer could possibly lead to an early diagnosis and an easier battle… Or peace of mind in knowing that they're healthy and there's nothing to worry about. She wanted you to know why she may not be at as many shows this tour. She's got an important battle to fight. Thank you for caring about my family so much that she would want me to share this information with you. I hope and pray that you never get news like this."