The 44-year-old was forced to reveal the information in a current law suit, in which she is suing former business manager for mismanaging her finances.
The 90210 actress claims she paid the company 5% of her earnings to manage her finances, but they failed to pay her medical insurance.
Shannen argues this resulted in a delay in her regular visits to the doctor, meaning she didn’t discover her cancer until it had spread.
She states that her current chemotherapy or mastectomy therapy could have been avoided.
Management company Tanner Mainstain released a statement in which they said:
"Tanner Mainstain is saddened to learn that Ms. Doherty is suffering from cancer and wishes her a full recovery.
"However, the claim that Tanner Mainstain caused her to be uninsured, prevented her from seeking medical care, or somehow contributed to her cancer is patently false. Tanner Mainstain will aggressively defend all of Ms. Doherty's claims in court."
Our thoughts are with Shannen and her family during this difficult time.