In his article in this issue of Cancer Cytopathology, Dr. Renshaw suggests that time has come for a drastic change in the cytologic policy toward Hürthle cell tumors.1 Such a change would be a distinct landmark in the diagnostic specificity of fine-needle aspiration cytology (FNAC). Unfortunately, we do not share Dr. Renshaw's optimistic view that FNAC alone can be used to subtype thyroid Hürthle cell tumors conclusively into malignant or benign tumors. Admittedly, the cytologic criteria given in Dr. Renshaw's article identifies all cases of Hürthle cell carcinoma in his relatively large series of this rare neoplasm and thus are of great interest in the cytologic evaluation of Hürthle cell tumors. However, it should be emphasized that the criteria are not stringent enough to identify Hürthle cell carcinomas only; approximately 67% of the adenoma cases and 25% of the cases of nonneoplastic Hürthle cell metaplasias were found to fulfill the cytologic criteria for a “malignant” tumor. It therefore is possible that these patients will not only be given a false malignant diagnosis that may be a psychologic trauma but also possibly be subjected to unnecessary extensive surgery. Today there appears to be a consensus that follicular adenoma and Hürthle cell adenoma can be treated safely with lobectomy.2 In the case of Hürthle cell carcinomas, the treatment of choice varies but a total thyroidectomy is favored by many surgeons.2 Thus, if Dr. Renshaw's suggestion is followed, it will lead to the overtreatment of a large number of patients with benign Hürthle cell nodules, unless there is a change in policy among surgeons with regard to lobectomy in all cases of Hürthle cell tumors irrespective of their malignant potential. Nevertheless, we cannot support Dr. Renshaw's recommendation. Given that the criteria and figures presented hold in a larger study, the diagnostic accuracy in diagnosing Hürthle cell carcinoma would be < 50%. Such an accuracy rate most likely would be subject to criticism and lead to an unnecessary debate regarding the usefulness and accuracy of FNAC in diagnosing thyroid tumors.
However, the criteria for Hürthle cell carcinoma are potentially significant and may, if they are used in conjunction with other parameters, lead to a considerable increase in specificity in the diagnosis of Hürthle cell carcinomas on FNA material. One such parameter is the rate of cell proliferation as measured by antibodies to Ki-67, which has been shown to be nearly threefold higher in carcinomas compared with adenomas.3, 4 If these findings can be corroborated in larger series of Hürthle cell tumors, it raises the hope that they may be separated into benign and malignant lesions with an improved accuracy. There also is a possibility that tumor cell expression of other markers such as HBME-1 and various oncogenes may differ between benign and malignant Hürthle cell lesions and consequently improve the diagnostic accuracy.
Finally, when discussing the possibility of a better gold standard for Hürthle cell neoplasms, let us drop the unspecific descriptive term “Hürthle cell,” which originally was used to describe C cells.5 Oncocytic tumors most likely are the best name for these tumors. Although oncocyte means “swollen cell,” it refers to variants of follicular cells in the thyroid and therefore is, in our opinion, a more appropriate name.