Most thyroid lumps in adults from iodine-poor areas of Russia are harmless, and only a tiny fraction look suspicious for cancer under the microscope.

In some parts of Russia where people don’t get enough iodine, lots of adults have lumpy thyroid glands, and most of those lumps are harmless. In two areas, Chechnya and Tula, over half and nearly half of adults had these lumps when checked with scans and tests.