Three weeks after Sophia Bassan’s mastectomy, she felt a stabbing pain beneath her right armpit. In the following months, painful shocks radiated through her chest and back. Her body became so sensitive that at times she couldn’t wear a shirt or lift a fork to her mouth. Bassan slept sitting up because it hurt to lie down, and she would flinch at the slightest touch. “I remember thinking I was losing my mind,” said Bassan, 43. “One time I was in so much pain that I had to take off my top, and then my cat’s tail brushed against my back. I screamed.” Mastectomies are lifesaving surgeries that remove a patient’s breasts to treat breast cancer, which affects 1 in 8 American women over their lifetimes, according to the American Cancer Society. Some women also undergo mastectomies as a preventive measure after a genetic test shows they have an increased risk for breast cancer. In the months following surgery, many women are afflicted by post-mastectomy pain syndrome, or PMPS, which spans from uncomfortable to disabling and can last years. Yet PMPS is inconsistently diagnosed and treated, leaving women like Bassan in agony as they hunt for relief and struggle to find doctors who take their pain seriously, according to a KFF Health News review of peer-reviewed research studies and interviews with pain specialists, surgeons, patients, and patient advocates. Another problem is that PMPS is poorly defined, which contributes to the wide range of estimates for how common it is, reaching…