UPDATE: The firm at the center of Shannen Doherty's lawsuit has released the following statement in response to the allegations:
"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."
Doherty has been diagnosed with breast cancer.
In a lawsuit filed by the former Beverly Hills, 90210 actress, Doherty claims that accounting firm Tanner, Mainstain, Glynn & Johnson failed to pay for her SAG medical insurance without her consent or knowledge.
The 44-year-old further alleges that the firm pocketed her 5 percent earnings, which she paid them as a result of managing her finances, and withheld money that was normally used to pay her medical insurance for themselves.
According to court documents obtained by E! News, Doherty says that they ignored an invoice for payment of the premium in early 2014, causing SAG cancel her insurance.
At that point, Doherty claims, she was unable to re-enroll in the SAG insurance program until 2015.
This past March, however, upon getting her insurance back in order, Doherty visited a doctor who discovered that she had "invasive breast cancer metastatic to at least one lymph node."
The television actress also noted that doctors said her cancer likely spread last year, during the time when she was uninsured, and would have been far easier to treat had it been detected earlier.
She details how she will soon be receiving chemotherapy and will undergo a mastectomy as well.
Per court documents, Doherty cut all ties with the management firm on Feb. 7, 2014, after learning of the lapse in payment.
She is looking for compensatory and restitutionary damages, according to the lawsuit. TMZ was the first to report the story.
—Additional reporting by Baker Machado