Shannen Doherty revealed a breast cancer diagnosis in a lawsuit claiming that a likely mastectomy and chemotherapy treatment potentially could have been avoided had her health insurance coverage been kept up-to-date.

The 44-year-old Beverly Hills, 90210 star claims that her former management company is to blame for an alleged lapse in her healthcare insurance. Allegedly, it was during this lapse that she went without a regular checkup, giving the cancer a chance to spread.

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The filing alleges that "in Nov. 2013, SAG sent the premium invoice to management firm Tanner Mainstain for Plaintiff's medical insurance coverage for the year 2014. However, Defendants ignored it, failed to pay it (without informing Plaintiff) and then promptly terminated their relationship with [Doherty] effective Feb. 7, 2014."

Doherty claims that at first she didn't realize that she was uninsured, and when she re-enrolled with SAG insurance for 2015 and was able to see doctors again under its coverage, that was when she was given her cancer diagnosis.

The complaint further claims that "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 (including mastectomy and chemotherapy) that Plaintiff will likely have to suffer through now."

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Her lawyer, Devin McRae, gave a statement to ET, saying, "The relationship between a business manager and its client is based on trust, in honesty and competence. That trust was violated here, and we hope that the defendants will correct it in a responsible manner."

Tanner Mainstain also issued a statement to ET, which reads, "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."

McRae is also representing Doherty's husband, photographer Kurt Iswarienko, in a separate lawsuit against Tanner Mainstain. The second lawsuit claims that the management company failed to make payments on a mortgage loan and allegedly missed credit card bill payments, causing a "quick foreclosure" and sending his credit rating into a nosedive.