But the F.D.A. said it could not state conclusively that textured implants were the sole cause of the disease, because there was not complete information in every case on what type of implants were used. Implants often have to be replaced, and if a woman with lymphoma has had both types of implants it may be hard to tell which is to blame.

A “consumer update” by the F.D.A. on Wednesday describes the lymphoma but makes no mention of texturing or its role in the disease. An agency spokeswoman, Stephanie Caccomo, said the F.D.A. would “take another look at” the update, adding, “Our goal is not to gloss over anything, but to be consumer friendly.”

Mark Marmur, a spokesman for Allergan, a major manufacturer of breast implants, said by email that the company was paying for research by outside investigators into causes of the lymphoma, working with plastic surgery societies on improved surgical techniques, adding information about the disease to its labeling and website, and giving surgeons educational materials for patients. He also said that on Jan. 1, Allergan changed the warranty on its textured implant to cover treatment for Allergan patients who received a diagnosis of the implant-associated lymphoma on or after that date, regardless of the implantation date.

A request for comment to the other major manufacturer of breast implants, Mentor, was not answered in time for publication.

The case count is uncertain, the agency said, noting that the F.D.A. depends on voluntary reporting that “may contain incomplete, inaccurate, untimely, unverified, or biased data.” Indeed, a registry called Profile, being compiled by professional societies in plastic surgery, is reporting higher figures — about 500 cases worldwide, and 16 verified deaths, including five deaths in the United States.

In an interview, Dr. Binita Ashar, director of the division of surgical devices in the drug agency’s Center for Devices and Radiological Health, said that the Profile registry might include data that the F.D.A. had not yet received, and that the agency and professional groups were collaborating to obtain more accurate information about the disease.

Compared with the number of women with breast implants, the number of lymphoma cases is very small. In the United States, about 300,000 women a year get implants for cosmetic reasons, and another 150,000 for reconstruction after cancer surgery. Worldwide, about 10 million women have implants.