Inside the Shannen Doherty Breast Cancer Lawsuit

— -- Actress Shannen Doherty is accusing her former business managers of being "crooked" and claims in a new lawsuit that they not only stole from their clients but "habitually blundered" the tasks they were hired for, including paying her insurance premiums.

The 44-year-old "Beverly Hills, 90210" star revealed Wednesday that she is battling breast cancer that she says worsened because her former business managers allowed her health insurance to lapse.

"This is a case about crooked business managers who not only stole from their clients but habitually blundered the most critical tasks of the profession," alleges the lawsuit filed Wednesday against Tanner Mainstain Glynn & Johnson and its former business partner Steven D. Blatt.

A lawyer for the firm denied the company caused Doherty's health insurance to lapse.

"Tanner Mainstain is saddened to learn that Ms. Doherty is suffering from cancer and wishes her a full recovery," Randall Dean said in a statement to ABC News. "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."

Blatt declined to comment to ABC News.

In documents obtained by ABC News, Doherty alleges that instead of providing "experience," "commitment," "professionalism" and "stability" to clients primarily in the entertainment and professional sports industries, "the firm and former partner Blatt specialize in fleecing actors and entertainment industry professionals."

According to the court papers, the actress hired the firm in July 2009 for tax, accounting, investment and other business management services, including payment of her insurance premiums to the Screen Actors Guild.

She alleges that Tanner failed to pay her premium for 2014 after receiving an invoice in November 2013. The firm then terminated its relationship with Doherty in February 2014, after which time she discovered that her insurance premium had not been paid and she was "completely uninsured" until the next SAG re-enrollment period for 2015.

As a result, Doherty states, she did not visit the doctor regularly in 2014.

When she did return for a checkup in March 2015, doctors discovered that she had "invasive breast cancer metastatic to at least one lymph node," she states in the lawsuit. She adds that she was told that her cancer had spread during 2014 and "had she been insured and able to visit her doctor, the cancer could potentially have been stopped, thus obviating the need for the future treatment (mastectomy and chemotherapy) that [she] will likely have to suffer through now."

The star claims that she has not only incurred significant medical expenses as a result but has been unable to work and has been caused "severe emotional distress."

She says she has also discovered numerous discrepancies since severing ties with the firm, including "unexplained transfers," overcharging of thousands of dollars in management fees and failure to file taxes on time, resulting in liens and audits.

Doherty is asking for compensatory and punitive damages as well as attorney's fees.