Histopathologic assessment of thyroid tumors can lead to stage migration. We assessed frequency of pathologic upstaging, and associations with patient and tumor factors.

Primary thyroid cancers treated between 2013 and 2015 were included from our institutional cancer registry. For tumor, nodal, and summary stage, upstaging was present when final pathologic stage was greater than clinical staging. Multivariate logistic regression and Chi-squared tests were performed.

5,351 resected thyroid tumors were identified. Upstaging rates for tumor, nodal, and summary stage were 17.5% (n = 553/3156), 18.0% (n = 488/2705), and 10.9% (n = 285/2607), respectively. Age, Asian race, days to surgery, lymphovascular invasion, and follicular histology were significantly associated. Upstaging was significantly more common after total vs partial thyroidectomy, for tumor (19.4% vs 6.2%, p < 0.001), nodal (19.3% vs 6.4%, p < 0.001), and summary stages (12.3% vs 0.7%, p < 0.001).

Pathologic upstaging occurs in a considerable proportion of thyroid tumors, most commonly after total thyroidectomy. These findings can inform patient counseling.