"Benefiting from early detection through a doctor-ordered MRI, the cancer is not life threatening," E!online quoted publicist Ame Van Iden as saying.
"Christina is following the recommended treatment of her doctors and will have a full recovery," the publicist added.
Issuing a statement in this regard, the publicist also said that Applegate would maintain her regular shooting schedule on the sitcom 'Samantha Who' while undergoing the treatment.
The surprising revelation came only a short time after Applegate was announced as one of several celebrities to participate in the upcoming 'Stand Up To Cancer' benefit to air on NBC, ABC and CBS on September 5.
Applegate's singer-actress mother Nancy Priddy is also a breast cancer survivor.
Nancy was first diagnosed when Applegate was seven, and reportedly underwent a partial masectomy.