California: Identical Twins Diagnosed With Identical Breast Cancer Just Weeks Apart

Two identical twins were both diagnosed with breast cancer within the space of just three weeks, according to reports.

Hanna Thompson and Metta Siebert—both 35 years of age—are what's known as "mirror image" twins, ABC7 News reported.

Essentially, these are identical twins who have the same physical features but some appear to be in opposition, almost like a reflection.

"For example, if one twin is right-handed the other twin may be left-handed. Their hair whorls may curve in opposite directions," Roberta Spiro wrote in a blog post for the Washington State Twin Registry.

"Their first teeth may appear in opposite parts of the mouth. Their fingerprints may be mirror images—although identical twins do not have identical fingerprints," she wrote. "In extremely rare cases, one twin may have internal organs on the usual side, while the other twin has them on the opposite side."

The cancers that the twins have been diagnosed with also follow this rule.

"For masses, she actually has the mass on her left side. I have it on the right side," San Francisco resident Thompson—who won a silver fencing medal at the Beijing Olympics in 2008—told ABC7. "We're like the super special identical twins and we're clearly taking that way too far."

It is not unusual for twins to receive similar cancer diagnoses due to their genetic similarities. But for the diagnoses to come so close together is almost unheard of, doctors said.

"To say it was a one-two-punch was an understatement," Siebert told ABC7 from her home in Kansas City.

The sisters now know that they have a gene mutation known as BRCA2 which can increases the risk of them developing breast cancer by 70 percent over the course of their lives compared to the general population.

"This is very young, but this is what we see with a BRCA mutation," Dr. Pamela Munster, an oncologist at UCSF Medical Center in San Francisco where Thompson is being treated, told ABC7.

"Maybe this has all been an opportunity because one of the twins that was diagnosed can now tell the other one to get tested, and hopefully we can detect the tumor much sooner," she said. "I think one twin was lucky to have another twin and I think most twins would think they're lucky to have another twin anyway."

With the benefit of hindsight, the twins say they wished they got tested for the mutation previously.

"I just wish I knew a little bit more about that because it could have changed our treatment a little bit," Siebert said.

Nevertheless, the twins say that being diagnosed at similar times has made coping with the difficult situation slightly easier.

"Not that I would wish it upon her," Siebert said, "but it maybe makes it a teeny bit easier."

Hanna Thompson
USA's Hanna Thompson (center) and teammates Emily Cross (left) and Willette Doris (right) celebrate after winning the women's team foil semi-final match against Hungary on August 16, 2008 at the Fencing Hall of National Convention center, as part of the 2008 Beijing Olympic Games. PHILIPPE DESMAZES/AFP/Getty Images