Shannen Doherty is set to undergo surgery yet again, a year after announcing her cancer was in remission.

The 47-year-old actress has taken to Instagram to share a photo of herself with her doctor ahead of an upcoming surgical procedure, which comes just over a year after she told fans in April 2017 that the breast cancer she had been battling since 2015 was finally in remission.

Shannen didn't reveal what the surgery would be for, but informed fans that her doctor had recommended she use autologous blood banking - which means storing your own blood - ahead of the procedure.

The 'Charmed' star captioned the snap: ''My doctor had me bank some blood for my upcoming surgery. Mars P was patient with me and didn't even roll his eyes at my anxiety over the needle size. He was patient, kind and really good. (sic)''

Whilst Shannen was in the hospital she learned of the kind deeds of blood donators, and vowed to start giving blood as long as she is healthy.

Her post continued: ''As I sat there banking blood for myself, I asked him about some of the people also donating... especially the ones with TVs. So two of them come every 2 weeks and donate platelets which takes 2 hours. Another girl comes as often as allowed to donate blood. To say I'm moved by the generosity of people is an understatement. I'm vowing that as long as I'm cleared in the future, I will start donating. Thank you to those selfless humans that donate. Thank you to Mars and all at the clinic in Woodland Hills for your smiles and hard work. Thank you to the @americanredcross #humbledagain. (sic)''

Shannen was given the all clear on her cancer diagnoses in April last year after undergoing eight rounds of chemotherapy and radiation treatments, as well as a single mastectomy.

But despite being healthy again, the star said that since her health scare, every small amount of pain her body feels makes her worry, and admitted she has to keep pushing forward or else she risks letting the fear of the disease ''overtake'' her.

She said: ''You find yourself going, 'Oh, I have that pain too. Does that mean I'm getting bone cancer?' There's not a day that goes by that I don't wake up going, 'Oh, is this normal?' And then I sort of slap myself and go, 'OK, you're being silly.' The thing about cancer is that you have to just keep plowing through because it can really sort of overtake you.''