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Prognostic importance of histologic grading in papillary thyroid carcinoma
1Department of Pathology, Gade Institute, University of Bergen, Norway.
Background:
The influence of various clinicopathologic features on survival of patients with papillary thyroid carcinoma has been examined. In particular, histologic grade, which was obtained by a combined assessment of nuclear atypia, tumor necrosis, and vascular invasion (VAN score) was studied. According to this, histologic grade is independent of growth pattern and differentiation of the tumor cells.
Methods:
One hundred seventy-three consecutive patients were studied retrospectively, and most were treated with total/near-total thyroidectomy. Univariate (life-table) and multivariate (Cox regression) analyses of thyroid cancer deaths were performed.
Results:
Histologic grade showed a highly significant prognostic impact. It was possible to discriminate between low-grade (Grade 1) and high-grade (Grade 2) tumors, occurring in 79% and 21% of the patients, respectively. The risk of thyroid cancer deaths was found to be considerably higher in the latter group of patients. When histologic grade was combined with sex and age, a highly significant prognostic score (the SAG score) was obtained.
Conclusion:
Histologic grade based on nuclear atypia, tumor necrosis, and vascular invasion is a strong and independent prognostic factor. When combined with patient sex and age, the final SAG score and the pTNM-age classification were both significant and should be considered in prognostic stratification of these patients.