The 9/11 attack has produced another health nightmare — at least 15 men who were in the vicinity of Ground Zero defied astronomical odds and have been stricken with breast cancer.

Men account for only 1 percent of all breast cancers nationally.

Jeff Flynn is one of the unlucky ones.

Flynn, 65, was an account manager for data-storage company Dell EMC assigned to Goldman Sachs on Maiden Lane when planes smashed into the nearby World Trade Center towers.

He spent months around Ground Zero helping Goldman and other financial services firms get back up.

It was in 2011 — a decade later — when Flynn noticed a lump in his chest.

“I ignored it for a number of months. I didn’t even know men could get breast cancer,” he said.

While vacationing in Florida, his wife noticed that his left nipple was “inverting.”

When he returned home, he got a biopsy and was diagnosed with Stage 3 breast cancer. He underwent chemotherapy and radiation treatment and then had reconstructive surgery.

“During my mastectomy, surgeons excised 36 lymph nodes and 35 were cancerous,” Flynn recalled.

And his ordeal was far from over.

Three years later, a new lump appeared on his neck. Stage 4 cancer had invaded Flynn’s lymph nodes. That cancer is now being kept at bay with hormone shots and the cancer-fighting drug iBrance.

“I do feel like my breast cancer was related to exposure to 9/11 toxins. There’s no history of breast cancer in my family,” he said.

“I spent months breathing that crap in. You can wind up with any cancer from being down there.”

Flynn retired early because of his health problems.

He received a six-figure award from the September 11th Victim Compensation Fund, and the World Trade Center Health Program is helping cover the co-pays for his medications.

The Barasch McGarry law firm, which represents 9/11 health cases, said it has 15 male clients with breast cancer who either worked or lived around the World Trade Center.

Five are 9/11 responders, including two city firefighters, an NYPD sergeant, an ironworker and a highway repairman. Others worked for private businesses in the area and one was a student downtown at the time.

“It’s like cancer on steroids,” said lawyer Michael Barasch.

Among the victims is triathlete John Mormando, 51, a commodities broker who worked at the Mercantile Exchange until 2007.

Last year, he ran the New York Marathon and was preparing to compete in a full Iron Man contest when he noticed a lump on his chest.

“On March 23, I was diagnosed with breast cancer,” said Mormando, who is currently undergoing chemotherapy.

He had a mastectomy on his right breast and breast reduction on his left.

“There is a very strong possibility this is linked to 9/11. There’s not a history of cancer in my family,” he said.

A third breast-cancer victim, Leon Silverstein, 89, had both his breasts removed.

“I was a healthy man before,” said Silverstein, an Army veteran who has lived in Battery Park for 30 years.

The breast-cancer cases are just the latest tragic saga in the health woes of those who spent time at Ground Zero.

Nearly 10,000 people have suffered cancers linked to the toxic dust and smoke, the World Trade Center Health program reported.

In all, more than 1,700 responders and others affected have died, including 420 stricken with cancer.