Having an identical twin means you share a lot of similarities. But Hanna Thompson and Metta Siebert could never imagine that they would be diagnosed with breast cancer within three weeks of each other, reports ABC7NY.

The 35-year-old sisters are identical mirror-image twins. One is left-handed and the other right-handed; one has a stronger left eye, the other a stronger right one. “We’re like super special identical twins and we’re clearly taking that way too far,” Thompson told ABC 7. “She actually has the mass on her left side. I have it on the right side.”

Both Thompson and Siebert learned they have the BRCA2 gene mutation. (Women with BRCA1 or BRCA2 mutations are 70% more likely to develop breast cancer in their lifetime. What’s more, a diagnosis often comes at a much earlier age.)

According to Pamela Munster, an oncologist at the University of California, San Francisco who is co-leader of UCSF’s Center for BRCA Research, similar breast diagnoses of identical twins isn’t unusual, but the timing in this case is rare.

She believes this story has a lesson for other identical twins. “Maybe this has all been an opportunity because one of the twins that was diagnosed can now tell the other to get tested, and hopefully we can detect the tumor much sooner,” Munster said.

The twins wish they had been tested for BRCA earlier because earlier detection may have made a difference, if only by a little. According to Good Morning America, the sisters are undergoing different types of chemotherapy for Stage IIA breast cancer. Both twins plan to have a double mastectomy once their chemo is completed.

But right now, they’re both glad to have one another, despite being 2,000 miles apart—Thompson lives in San Francisco and Siebert in Kansas City. Siebert said, “Not that I would wish it upon her. But it maybe makes it a teeny bit easier.” As for Thompson, “There’s no other person I’d rather be going through it with than my twin sister.”

Click here to read how a mother and son supported each other through each other’s cancer.