The heartbreaking story behind Shannen Doherty's cancer diagnosis.

Beverly Hills, 90210 and Charmed actress Shannen Doherty got the world talking yesterday when she shared an emotional series of photographs on her Instagram account.

In the six-part photo series, the 44-year-old actress documented the process of shaving her hair as part of her treatment in her battle with breast cancer.

The photos offer an eye-opening and extremely personal look at one of the most emotional parts of any person’s cancer treatment.

But the story behind Doherty's cancer diagnosis, and the reasons why she wasn't able to seek treatment sooner, are just as heartbreaking.

Shannen first revealed her diagnosis in a lawsuit filed in mid-2015, which revealed her management had failed to keep her health insurance up to date.

"In Nov. 2013, [the Screen Actor's Guild] sent the [health insurance] 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," the lawsuit claimed.

The actress claims she wasn't able to see her doctor for regular checks while she was uninsured, and it wasn't until she was able to re-enrol with the Screen Actor's Guild in 2015 that she could seek treatment, by which stage her breast cancer had already progressed.

"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," the lawsuit read.

"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."

Doherty went public with her diagnosis in September 2015, releasing a statement to People magazine.

“I am continuing to eat right, exercise and stay very positive about my life,” she said.

“I am thankful to my family, friends and doctors for their support and, of course, my fans who have stood by me.”

Protect yourself by learning how to perform a self-breast check...