It was supposed to be a quick trip to the King of Prussia mall Sunday to pick out clothes for a funeral. It ended with an escort off mall property after a clash of individual expression and corporate sensibilities.

At issue were black caps worn by two sisters - Zakia and Tasha Clark of North Philadelphia - mourning the loss of their mother, Jackie Underwood, to cancer May 14. The hats were imprinted with "F- Cancer" in pink, with a breast-cancer-awareness ribbon taking the place of the letter C.

A security guard approached the two sisters, who were with a third sibling, Makia Underwood, while they were eating in the food court, and told them in no uncertain terms to remove the hats or leave.

"He didn't ask nicely," Zakia Clark said.

When they resisted, the guard threatened to call police. More security arrived and the sisters were taken to the mall office. There, they were met by an Upper Merion Township officer who said they had to leave the mall. Police were waiting at their car to make sure they did.

In hindsight, mall officials do not think the situation was handled properly.

"I wish we had been more empathetic, sympathetic, and sensitive," said Les Morris, spokesman for the King of Prussia mall and its owner, Simon Properties of Indianapolis.

Morris said the mall stands by its commitment to provide a family-friendly atmosphere. He said the company has a policy banning offensive words on clothing in its malls.

Morris spoke with Zakia Clark on Tuesday to convey the organization's sympathies and apologize.

"They understand we get it, and we could have improved our approach," he said. This situation could have been handled with more flexibility and awareness of the family's grief, he said.

The mall supports charities fighting against cancer, including the American Cancer Society, Relay for Life, and corporate initiatives that benefit Susan G. Komen for the Cure, Morris said.

As a private organization, the mall was within its rights.

"If they wanted to, they could ban green shirts," said Mary Catherine Roper, senior staff attorney with the American Civil Liberties Union of Pennsylvania. A commercial facility can make its own rules as long as they do not discriminate on the basis of race or sex, she said.

A private commercial entity can control the message on its own property, she said.

"They don't want to be like a public street where anything goes," she said.

On Wednesday, Underwood, 51, was buried, her casket carried to Chelten Hill Cemetery on a horse-drawn hearse followed by 90 cars of mourners.

Zakia Clark said she bore no ill feelings toward the mall and had accepted the apology. However, she has no respect for mall security, she said.

The family had planned a protest at the mall at 7 Thursday night, she said. It will now hold a peaceful rally instead.

Steven Alston, 31, Jackie Underwood's nephew, said four other family members have died from cancer. He wore a "F- Cancer" shirt and hat at her funeral.

"Cancer has no race, color, or creed. It is something that affects anyone," he said. His cousins "wanted to express themselves. It was the right cause and not a poor choice of words."

Contact Sulaiman Abdur-Rahman at sabdur-rahman@phillynews.com, or follow on Twitter @sabdurr.