July 30 (Reuters) - Johnson & Johnson said on Wednesday it plans to ask doctors to return its power morcellators, a controversial surgical device that may inadvertently spread cancer in women being treated for uterine growths called fibroids.

J&J's Ethicon unit in April suspended sales and distribution of the devices while their role in treating symptomatic fibroid disease is reviewed by the U.S. Food and Drug Administration and the medical community. The FDA had advised doctors not to use the devices pending further review.

On Thursday, J&J will take the further step of reaching out to customers to ask them to return the devices they have already purchased in what it is calling "a worldwide market withdrawal" of all Ethicon morcellation devices that remain on the market, an Ethicon spokesman said.

The morcellators are used to cut up the uterine growths so they can be more easily removed using non-invasive procedures. They are also used in hysterectomies.

However, the masses may sometimes be malignant, which is often not detected prior to surgery, and the spinning blade of the morcellators could spread deadly cancer and worsen patient outcomes, the FDA had warned.

"Due to this continued uncertainty, Ethicon believes that a market withdrawal of Ethicon morcellation devices is the appropriate course of action at this time until further medical guidelines are established and/or new technologies are developed to mitigate the risk," the company said in an e-mailed statement.

(Reporting by Bill Berkrot; Editing by Dan Grebler)