Justice Ruth Bader Ginsburg is still recuperating from cancer surgery and was not on the bench Monday when the Supreme Court began a round of oral arguments, the first time in her career as a justice that she has missed a session.

“Justice Ginsburg is unable to be present today,” Chief Justice John G. Roberts Jr. announced as the court began its session.

Ginsburg is working from home, according to a court spokeswoman. Roberts said she will participate in the two cases that were scheduled for argument by reading briefs, filings and a transcript of the sessions.

Ginsburg, who joined the court in 1993, has had several health scares during her time on the Supreme Court, but had not missed a day of scheduled oral arguments until now. The court also has arguments scheduled for Tuesday and Wednesday, and it is unclear when she will return.

A Supreme Court spokeswoman says Justice Ruth Bader Ginsburg is recovering after she had two cancerous nodules removed from her lungs Dec. 21.

She had surgery Dec. 21 for two malignant nodules in her left lung, the 85-year-old justice’s third bout with cancer.

The pulmonary lobectomy was performed at Memorial Sloan Kettering Cancer Center in New York. She was released several days later and has been working at home, according to court spokeswoman Kathleen Arberg.

The two nodules in the lower lobe of her left lung were discovered during tests performed at George Washington University Hospital after Ginsburg fell and broke three ribs on Nov. 7.

In a pulmonary lobectomy, a lobe of the lung is completely removed. The right lung has three lobes and the left has two.

John Kucharczuk, a thoracic surgeon at the University of Pennsylvania, said the usual recovery time for such a surgery is six to eight weeks, so it wasn’t surprising that Ginsburg missed arguments. He said even younger patients are “tired and washed out” after the operation and some require pain medications.

Ginsburg was treated for colorectal cancer in 1999, and pancreatic cancer was discovered at a very early stage 10 years later. She scheduled treatment for both during the court’s off days.

Near the end of 2014, she had a heart stent implanted.

Cancer specialists say the kind of surgery Ginsburg underwent is performed only when the doctors are convinced the cancer has not spread to other organs — in that case, the treatment would be a systemic therapy like chemotherapy.

The court has not said whether further treatments are planned.

Ginsburg is the oldest member of the court and the longest-serving of the court’s four liberals.

“As long as I can do the job full steam, I will do it,” Ginsburg said last year. She has hired law clerks through the 2020 term.

Laurie McGinley contributed to this report.