She was in middle school in March 2011, when three reactors melted down at the Fukushima Daiichi nuclear power plant about 40 miles from her home in northern Japan. Living outside the evacuation zone, she continued to go about her life, shopping and cycling to school.

Four years later, a screening found a malignant tumor in her thyroid, a gland in the neck that is known to be vulnerable to radioactive particles released during a nuclear accident. But when she got the diagnosis, a doctor told her immediately that the growth was unrelated to the disaster.

She wondered how the doctor could judge that without making further checks. (The young woman, now in her 20s, asked that her name not be used because she has faced intense social pressure not to speak out.)

Her question is one that has not been conclusively resolved 14 years after a huge earthquake and tsunami knocked out cooling systems at the plant, leading to explosions at its reactor building that showered this region of northern Japan with radioactive particles.

A few weeks ago, the Fukushima Prefecture screening committee restated its conclusion that the triple meltdown has not caused long-term health effects. Many medical experts, including those at international agencies, have made similar findings. But there is skepticism from many residents and a minority of medical experts, who say the authorities haven’t done enough to prove their case.

The young woman from Fukushima has joined six other people with cancer in a lawsuit to seek compensation from the plant’s operator, Tokyo Electric Power Co. The company says there’s no scientifically proven link between the cancers and radioactive particles released by the disaster. The next hearing will be held on Sept. 17, though a ruling is probably years away.