The F-word made its debut on T-shirts at a papal general audience on Wednesday and a laughing Pope Francis gave members of the choir wearing them VIP treatment.
About 30 Italians wearing red T-shirts bearing the words "Fuck Cancer Choir" sat in a front section at the audience in St. Peter's Square and later sang for the pope.
Below the phrase was a clenched fist punching through a background of musical notes.
At the end of the audience before thousands of people, the group went up to the platform from where Francis had addressed the crowd and sang for the seated pope, standing around his chair.
"You are good, you are poets, thank you," the pope, laughing, told them, a video on their Facebook page showed.
The choir, from the northern Italian province of Alessandria, is led by two doctors, biologist Stefania Crivellari and onocologist Federica Grosso.
The area has had a higher-than normal rate of mesothelioma, a type of cancer caused by exposure to asbestos in the past from a now-closed factory in the town of Casale Monferrato.
"We know what the word means in English but it was chosen by our patients to show that there is a possibility of living with cancer in a human way, all together," Grosso told Reuters.
She said the group, which has been on Italian television to push for more acceptance of people living with cancer, is preparing a musical based on individual stories of survivors. It will debut this autumn.
The group's Facebook page says its mission is to "transmit energy and strength" to cancer patients and raise funds for research.