Researchers retested tumor samples from a large group of women and found that 22 out of 530 women had their tumor type incorrectly classified, which precluded them from effective treatment options. The repercussions of incorrectly identifying a cancer’s subtype are considerable. “While it is comforting that only four percent of these women were misclassified initially, this is an enormous issue for those who fall into this group,” said one researcher.