CORRECTION: 5/25/2013 11:30 A.M. EDT. The subheadline of the original version of this article incorrectly stated that Proskauer Rose terminated Elly Rosenthal shortly after she returned from a medical leave in 2008. In fact, Rosenthal was terminated in 2011, roughly three years after the medical leave in question. The subheadline has been revised to reflect the correct information. We regret the error.

A former Proskauer Rose chief financial officer who sued the firm in 2011 alleging that various forms of discrimination led to her termination has whittled the claims contained in her initial suit to a single allegation: that the firm forced her out over a medical leave she took in 2008 after being diagnosed with breast cancer.

Elly Rosenthal, who worked in Proskauer’s finance department for more than 18 years, sued her former employer for $10 million in October 2011, seven months after she was fired. At the time Rosenthal claimed she was a victim of age, gender, and disability-related discrimination.

Earlier this year, Rosenthal, 59, amended her complaint to focus exclusively on the disability claim, which alleges that “she was marginalized by superiors and coworkers and then terminated” after taking a three-month medical leave in 2008 in order to recover from treatment for cancer, including two rounds of surgery.

Proskauer representatives have called Rosenthal’s suit “meritless” and deny discriminating against her. The firm faces a May 30 deadline to respond to Rosenthal’s amended complaint. A firm spokeswoman declined to comment Thursday.

Rosenthal’s lawyers at employment firm Sanford Heisler did not immediately respond to requests for comment Thursday about why Rosenthal narrowed her allegations. Her lawyer, David Sanford, told The Am Law Daily in 2011 that he expected to find evidence of gender and age discrimination during the discovery process that would show people in similar circumstances at the firm who are male or younger “have not been treated in similar ways.”

Rosenthal joined the firm as director of finance in 1992 following two decades of work as an accountant at law firms, including Stroock & Stroock & Lavan and now-defunct Finley, Kumble, Wagner, Heine, Underberg, Manley, Myerson & Casey, and at accounting firm KPMG. She became Proskauer’s chief financial officer in 2005.

The trouble started, Rosenthal alleges in her complaint, even before she returned from medical leave—despite assurances from her boss, Proskauer chief operating officer Art Gurwitz that “there will always be a place for you” at Proskauer.

At a meeting on June 16, 2008, a month before Rosenthal was scheduled to return to work, Gurwitz told her he planned to reorganize the firm’s administrative staff, according to the complaint. “Interested in challenging herself after many years in the same position,” Rosenthal told Gurwitz “that she would be willing to consider an altered or new role at Proskauer,” the complaint states.

As part of that reorganization, Rosenthal was given the newly created title of chief administrative financial officer, a position that ranked below that of the firm’s new CFO, Jim Barbaria. Rosenthal alleges that Barbaria, who had previously been manager of financial analytics, was less qualified than her for the CFO job because he was not a certified public accountant and had never been the head of a finance department.

Rosenthal says in her complaint that at a meeting that December she agreed to take a 10 percent pay cut, to $423,000, because she was working less than five days a week after returning from medical leave. (Her salary ultimately dropped to $420,000.) During the same meeting, she alleges, Gurwitz told her she would not receive a bonus or merit increase as a way “of offsetting the three months of paid medical leave.”

In a 2009 performance evaluation, Rosenthal received mixed reviews from Gurwitz, according to the complaint. While being told that her history with Proskauer made her a good fit for her new job, Gurwitz also said he suspected “it is difficult to now be in a new management role at a time when the industry is changing—rapidly—and as a firm we are modifying/integrating/enhancing/eliminating” many procedures and processes to which Rosenthal was accustomed, the complaint says, quoting from a written review that Proskauer has verified in court filings as accurate.

Following that review, Rosenthal alleges, rather than help her adapt to her new role, Gurwitz, Barbaria, and others “orchestrated a concerted campaign to undermine Ms. Rosenthal’s authority.” For example, Rosenthal says, when Proskauer moved its new midtown Manhattan headquarters at 11 Times Square in 2011, the firm exiled her to an office eight blocks away at 2 Penn Plaza.

Rosenthal says she received an email on March 11, 2011, asking her to meet with Gurwitz the following day. At that meeting, Gurwitz, with New York managing partner Bruce Lieb present, told her there was “no role” for her at Proskauer and that she was being terminated. The complaint states that Gurwitz gave her three days to clear out her office.

“Proskauer’s abrupt dismissal of Ms. Rosenthal, without warning of any kind, despite her nearly two decades of loyal service to the Firm, constitutes malicious or recklessly indifferent treatment,” the complaint states.