4th Annual Baby2Baby Gala Honoring Kerry WashingtonActress Shannen Doherty has been fighting breast cancer for more than a year, and now, the former "Beverly Hills, 90210" star has revealed that the disease has spread.

In an interview with ET, Doherty discussed her battle, revealing that after she had a single mastectomy in May, her doctors discovered that she was not out of the woods yet.

"I had breast cancer that spread to the lymph nodes, and from one of my surgeries we discovered that some of the cancer cells might have actually gone out of the lymph nodes," Doherty told ET. "So for that reason, we are doing chemo, and then after chemo, I'll do radiation."

The actress, who was diagnosed in February 2015, has completed three of eight chemotherapy treatments so far. Last month, she made the decision to shave her head, after her hair started falling out. Doherty documented the entire process on Instagram in an intimate series of photos, a decision she said helped her control her own message, but also hopefully inspires others going through a similar process to keep fighting.

"I wanted to put it out there the way it felt the best for me to put it out there," Doherty told ET. " ... It's easier to live with having cancer if I know I'm helping at least one person."

Read the entire emotional interview here.

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