The day before she was scheduled to go back to work after recovering from a mastectomy, Vivienne Parra got a phone call from her supervisor.

According to Parra, her boss fired her, and four days later, sent her a termination letter saying it was because Parra never followed up on that phone conversation to tell her boss she wanted to keep her job.

The real reason they fired her, Parra claims, was because she had taken sick leave to seek treatment for breast cancer. Parra is now suing Sentara Northern Virginia Medical Center in Woodbridge for violating federal laws that protect workers with disabilities from workplace discrimination.

A spokeswoman for Sentara said Parra’s claims predate the current leadership at the company. Sentara acquired Potomac Hospital in December 2009; Parra’s claims arise from decisions managers at Potomac made in September 2009.

“We do take these allegations seriously, and are investigating the facts and circumstances behind [Parra’s] allegations,” said Sentara spokeswoman Robin Adams. She said the managers named in the lawsuit have since retired.

The Equal Employment Opportunity Commission, the federal agency that enforces anti-discrimination laws in the workplace, has found reason to believe Parra’s claims. Last summer, after a three-year investigation, the agency found “reasonable cause to believe that [Parra] was discharged based on her disability in violation of the [Americans with Disabilities Act],” read a March 2012 letter signed by EEOC Acting Director Mindy Weinstein. It is a relatively rare finding by the commission, which in 2011 reached such a conclusion for less than 5 percent of disability discrimination charges filed with the EEOC.

Parra’s lawsuit, filed last August in U.S. District Court for the Eastern District of Virginia, cites the Americans with Disabilities Act and the Family and Medical Leave Act, which require employers to accommodate workers with disabilities and protect the jobs of employees who take medical leave.

The number of charges against employers over alleged disability discrimination has ballooned steadily since 2005, according to the EEOC. That year, 14,893 such charges were filed with the EEOC; by 2011, that figure had jumped to 25,742, a record high.

“I was disappointed and very frustrated,” said Parra, who now lives in Southern California and works as a medical support staffer at a hospital there. “I hope the managers I worked for understand all I wanted was help from them so I could pursue what I needed to do to get better.”

According to the complaint, Parra’s boss indicated that Parra had not filed paperwork to request time off, and that she had run out of days to use. Parra worked at Sentara from 2006 to 2009 as a patient registrar and insurance verification specialist. She took her first leave in the spring of 2008 when she was diagnosed with breast cancer and underwent her first mastectomy and chemotherapy. She returned to to work the following January but was demoted, according to the complaint. In July 2009, she requested a second leave for her second mastectomy. It was just prior to Parra’s return from her second leave that she was fired.

The hospital’s alleged actions fit an a pattern that is becoming increasingly common in the post-recession economy, said Parra’s attorney, R. Scott Oswald of the Employment Law Group.

“We’re seeing more employees being terminated because they’re perceived to no longer be capable of their job duties, without any objective measure that is the case,” Oswald said. “I think the economy was the impetus. But what is happening now is there is a certain segment of corporate America that sees this as a legitimate business strategy.”