Shannen Doherty, best known for her work on Charmed and 90210, made a devastating revelation in August of 2015.

"Yes, I have breast cancer, and I am currently undergoing treatment," she said. "I am continuing to eat right, exercise and stay very positive about my life. I am thankful to my family, friends and doctors for their support and, of course, my fans who have stood by me."

It was hard for fans to watch Doherty, someone they admired so much, go through something so trying. Known for her strength, the actress tried to stay positive throughout the entire process. She had two rounds of chemotherapy to try and beat the disease, which caused her hair to fall out.

"After my second treatment, my hair was really matted, like in dreadlocks. And I went to try and brush it out, and it just fell out," she recalled. "I just remember holding onto huge clumps of my hair in my hands and just running to my mom crying, like, 'My hair, my hair, my hair, my hair.'"

Instead of letting the chemo win, Doherty decided to take action and shave her whole head.

"We did stages. We did a pixie," she said. "And then we did a mohawk, which was my favorite look. And then finally we had to get the shaver thing and just buzz it off."

In just under two years, Doherty announced that she was in remission from the terrible disease. In an Instagram post, she explained what that means.

Moments. They happen. Today was and is a moment. What does remission mean? I heard that word and have no idea how to react. Good news? YES. Overwhelming. YES. Now more waiting. As every single one of my fellow cancer family knows, the next five years is crucial. Reoccurrences happen all the time. Many of you have shared that very story with me. So with a heart that is certainly lighter, I wait. In the meantime, decisions. Reconstruction which is several surgeries. Decision on taking a pill for the next five years that comes with its own set of problems and side effects. I am blessed, I know that. But for now.... remission. I'm going to just breathe.

It seemed like Doherty was unstoppable from that point forward. She was back at work, and began celebrating the little things, like her first post-chemo haircut.

"After two years of either bald or a crew cut, it's nice to feel a bit more like a woman again. ❤️❤️❤️," she wrote in Instagram.

Doherty was back on the set of Heathers, the new TV show based off her hit movie from 1988, and shared a powerful message with her fans.

Good morning. It wasn't that long ago that I wondered if I would ever get to go back to doing what I love. Slipping into a character. Creating. Being on set, around the circus and feeling that deep satisfaction of accomplishment. This past week I worked 7 days. No weekend off and I loved every second. Yes I worked hard to get here but I'm also very blessed. Lucky, fortunate and not a day goes by that I don't thank God for this blessing of a life I have. So off to work I go with a full spirit. A spirit of gratitude and love and deep appreciation. There is beauty in everything.

But as any cancer patient will tell you, there are always tests to be done, and they do not always go the way you want them too. Unfortunately for Doherty, she just found that out the hard way.

On Tuesday night, Doherty posted a message on her Instagram page, which revealed the results of her tests.

Test and results. One Tumor marker test came back good. Other... elevated. Just means I get monitored and another test. But even after that call, I'm staying positive and taking stock of my life. It certainly helps put things in perspective and reminds you of what you learned thru the cancer journey. And I sometimes, need a refresher. As I've said before, cancer changes your life in ways no one could ever imagine.....btw, the elevation can be from all sorts of things. Oh and vitamin D... need more of that too. #stillacancerslayer

If Doherty is concerned about these results, she's certainly not showing it. As the actress mentions, there are many reasons tumor markers can be elevated. According to Carolyn Vachani RN, MSN, AOCN at The Abramson Cancer Center of the University of Pennsylvania, these are some things that can cause tumor markers to elevate, depending on where the tumor is located:

• Pregnancy
• Cigarette smoking
• Muscle injury
• IBS
• UTI
• Ulcers
• Marijuana use
• Anemia
• Certain medications
• Dietary intake

While Doherty is still being monitored for the elevation, one thing is for sure: she's a fighter. She's also been extremely open about her journey, which means when she knows something, so will we.