Jenna Fischer, the actress best known for her role as Pam Beesly in the popular television series “The Office,” said on Tuesday that she was diagnosed with Stage 1 triple-positive breast cancer in December but that she was now cancer free after successful treatment.
“I am now cancer free,’’ Ms. Fischer, 50, of Los Angeles, said in her announcement, imploring her nearly four million Instagram followers to consult with their doctors and schedule annual mammogram appointments.
“If I had waited six months longer, things could have been much worse,” Ms. Fischer said. “It could have spread.”
She said that she had surgery in January to remove the tumor that doctors had found. That was followed by “12 rounds of weekly chemotherapy” and “three weeks of radiation,” her post said.
“I’m happy to say I’m feeling great,” said Ms. Fischer, who is also an author and the co-host of a popular podcast about “The Office” with Angela Kinsey, a former co-star from the show. Ms. Fischer said she was continuing a treatment plan that includes infusions of targeted therapy.
A representative for Ms. Fischer declined a request for an additional comment from the actress on Tuesday.
In addition to her role in “The Office,” a television show that ran on NBC for eight years and is among the most popular shows in television history, Ms. Fischer has also acted in popular comedic films, including “Blades of Glory” and the movie musical version of “Mean Girls,” playing the main character’s mother.
Sprinkled within her post were jokes and references to her character on “The Office.”
“‘Take care of your ticking time bags,’” Ms. Fischer wrote, referencing a quote from Michael Scott, the boss of the paper company Dunder Mifflin in Scranton, Pa., where “The Office” takes place.
News of Ms. Fischer’s cancer diagnosis shocked fans, who wrote thousands of supportive messages in the comment section of her Instagram post. Ms. Fischer said she wore wigs to hide her hair loss so that she could keep her diagnosis private until she was ready to share the news.
Dr. Cesar Santa-Maria, a medical oncologist and associate professor of oncology at Johns Hopkins, reviewed Ms. Fischer’s post and said she had been diagnosed with an “aggressive subtype of breast cancer.”
“But because of the treatments we have now,” Dr. Santa-Maria continued, “it’s the most curable. Twenty years ago? Not the case.”
Catching the tumor early on, when it was in Stage 1, was critical for her to have a successful treatment, Dr. Santa-Maria said. Women at average risk for breast cancer should talk to their doctors about getting their annual mammograms beginning at age 40, he added.
“Again, don’t skip your mammogramsolare,” Ms. Fischer wrote, reminding her followers that October is Breast Cancer Awareness Month. She said that Michael Scott “was right. Get ’em checked ladies.”