US actress Jenna Fischer has announced she is cancer-free after battling an “aggressive” form of the disease.

The 50-year-old, who starred as receptionist Pam Beesly in the US version of The Office, opposite John Krasinski, said she was diagnosed with stage one triple positive breast cancer last December.

“After completing surgery, chemotherapy and radiation I am now cancer free,” she said in a statement on Instagram.

The TV star said she posted on Instagram last October in preparation for her routine mammogram with a joking reminder to “take care of your ticking time bags”, referencing Steve Carell’s character Michael Scott in the sitcom.

However, after inconclusive results, a biopsy was ordered which found the “aggressive form of breast cancer”.

“In January, I had a lumpectomy to remove the tumour,” she said.

“Luckily my cancer was caught early and it hadn’t spread into my lymph nodes or throughout the rest of my body, however because of the aggressive nature of the triple positive breast cancer it still required chemotherapy and radiation to be sure it didn’t return.”

Fischer said she had 12 rounds of chemotherapy in February and three weeks of radiation in June.

“I lost my hair during chemotherapy but thanks to some great wigs and hats with hair (which my family affectionately called Wigats) I have been able to wait until now to reveal all that has been going on for me,” she said.

Fischer said her best friend, Angela Kinsey, who starred as Angela Martin in The Office, “protected me and advocated for me” as the pair recorded their re-watch podcast Office Ladies.

“For a long time, she was the only person in my workspace who knew,” she said.

“When I lost my hair, she wore hats to our work meetings so I wouldn’t be the only one. When I needed a break, we took one.”

Fischer said her filmmaker husband Lee Kirk was “by my side through all of this”, and the couple celebrated the end of her cancer treatment with their two children, aged 10 and 13, by ringing a bell and throwing confetti in their back garden.

Concluding her statement, Fischer said “don’t skip your mammogram”.

“Michael was right. Get ’em checked ladies,” she added.