Bailed-out insurer American International Group on Monday said Chief Executive Robert Benmosche has cancer and has an unclear prognosis, casting another shadow on the company during a major restructuring.

AIG did not disclose what kind of cancer Benmosche, 66, has, but said he is undergoing “aggressive chemotherapy.”

Benmosche, in a statement, said he felt fine but said his long-term prognosis would not be clear until he had a couple more months of treatment.

Benmosche has been an authoritative presence at AIG since becoming CEO in August 2009, getting much of the credit for a turnaround that included selling foreign life unit ALICO at an attractive price to MetLife and sorting out the mess surrounding the failed sale of Asian unit AIA.

In July Benmosche won a boardroom battle with former Chairman Harvey Golub over the failed AIA sale. Reports indicated Benmosche had threatened to resign if Golub was not replaced.