Anaplastic transformation of papillary thyroid carcinoma in recurrent disease in regional lymph nodes: A histologic and immunohistochemical study

Background and Objectives: Although the prognosis of papillary thyroid carc inoma is favorable in most cases, recurrent disease in the regional lymph n odes is not uncommon, and some patients die of recurrent disease that ultim ately becomes unresectable. We studied the proliferative activity of cancer cells in recurrent foci in lymph nodes to see whether repeated recurrences might result in anaplastic transformation of papillary thyroid carcinoma. Methods: Fourteen patients with papillary thyroid carcinoma who underwent r eoperation for recurrent disease in the regional lymph nodes more than once were the subjects of the study. The histologic findings and proliferative activity of carcinoma foci at each recurrence were studied histologically a nd immunohistochemically. Results: There were higher incidences of histologic features of poorly diff erentiated thyroid carcinoma in the metastatic foci in the lymph nodes as i t recurred repeatedly, and the labeling indexes of proliferating cell nucle ar antigen (PCNA) and nuclear antigen Ki-67 (MIB-1) increased. Conclusions: These observations suggest that papillary thyroid carcinoma ma y become more malignant, even undergo transformation to an anaplastic varie ty, as metastatic disease in the regional lymph nodes recurs repeatedly. J. Surg Oncol. 1999;70:45-18. (C) 1999 Wiley-Liss, Inc.