Tall-cell variant of papillary thyroid cancer: disregarded entity?

The tall-cell variant of papillary thyroid carcinoma (TCV) has been described as an aggressive tumor with a significantly higher incidence of recurrence and mortality than other forms of papillary carcinoma. In some series it has accounted for up to 10%, whereas in other series it has not been reported at all, indicating that there are difficulties identifying it. In a series of 162 consecutively treated patients with papillary thyroid carcinoma treated by total thyroidectomy according to a highly standardized procedure, all specimens were specifically examined by an international group of pathologists to establish the occurrence of TCV. All patients with TCV were studied with regard to local aggressiveness, the presence of metastases, iodine uptake, DNA pattern, thyroglobulin production, treatment (surgical and adjuvant), and outcome (follow-up 3-17 years, median 10 years). At primary histopathologic evaluation by the local pathologist, three patients were recorded as having TCV. At special evaluation by the expert group, eight more cases were found, giving a total of 11 patients in this series (7%). Five of them had extracapsular growth, and four were multifocal. Three had metastases at the time of admission. Seven tumors were diploid, one tetraploid, and three aneuploid. Of the three patients with primary distant metastases two died (8 and 24 months after operation), and one is still alive after 10 years. Four other patients developed recurrences, one of whom died from cardiac failure, but the others have so far been treated successfully. Two of these recurrences had no radioiodine uptake, and one had no rise in thyroglobulin concentrations; the other two had rising values that correlated with recurrence. The other four patients are alive without recurrence. It was concluded that identification of the TCV requires examination by an experienced pathologist. Moreover, it may have a higher incidence than is generally recognized. No reliable criteria for prognostic classification were identified. The results suggest that early identification and active treatment can lead to an outcome more favorable than has previously been described.