TRENDING: Shannen Doherty Thanks Mom During Her Breast Cancer Battle

It will always be true that there is nothing like a mother's love to lift you up when you're down. Shannen Doherty penned a touching note via a tender black and white Instagram to her own mom for helping the 45-year-old actress through cancer treatments.

A photo posted by ShannenDoherty (@theshando) on

Doherty was diagnosed with breast cancer in March 2015, underwent a single mastectomy, and recently revealed that the cancer had spread to her lymph nodes. She's undergoing chemotherapy now, and has shared the process on social media.

>> Read more: New Breast Cancer Guidelines: Screen Later, Less Often

In July, the former "Beverly Hills, 90210" and "Charmed" star shaved her head, and posted a progression of Instagrams along the way.

A photo posted by ShannenDoherty (@theshando) on

A photo posted by ShannenDoherty (@theshando) on

A photo posted by ShannenDoherty (@theshando) on

A mother's love is pure, selfless and brave. What's something your own mother has done for you during difficult times? Share your thoughts in the comments below.