Hurthle cell carcinoma: A critical histopathologic appraisal

Purpose: Controversy exists over the ability of morphology to predict the b iologic behavior of Hurthle cell carcinoma. The aim of this study was to co nduct a critical histopathologic review of Hurthle cell carcinoma clad to c orrelate morphologic parameters with clinical outcome. Patients and Methods: Patients with histologically confirmed Hurthle cell c arcinoma treated between 1940 and 2000 form the basis of this study, Adenom as were excluded. Tumors of unknown malignant behavior ([UMB] n = 17) had s olid growth pattern, incomplete capsular invasion (Ci), or both but no vasc ular invasion (Vi). Minimally invasive carcinomas ([MIC] n = 23) herd one f ocus of intra- or extracapsular Vi, one focus of complete Ci, or both. Wide ly invasive carcinomas ([WIC] n = 33) demonstrated more than one focus of V i, more than one focus of Ci, or both. The primary end points were relapse- free survival [RFS] and disease-specific survival (DSS). Rates of recurrenc e/death were estimated by Kaplan-Meier method. The univariate influence of prognostic factors ore end points was analyzed by log-rank test, and multiv ariate analysis was performed by Cox regression. Results: Median fallow-up was 8 years. No patients with UMB or MIC relapsed or died of disease. Of WIG, 73% relapsed and 55% died of disease. Age, siz e, and extent of resection did not influence outcome. Adverse predictors of RFS and DSS among WIC were extrathyroidal extension, nodal metastasis, pos itive margin, and solid growth pattern (P < .05), Both Ci and Vi were assoc iated with worse DSS (P < .05). On multivariate analysis, extrathyroidal ex tension and nodal metastases were independent predictors of outcome (P < .0 5). Conclusion: Patients with Hurthle cell carcinoma have a prognosis that is p redicted by well-defined histomorphologic characteristics. Unlike different iated thyroid cancer, nodal metastases predict a worse outcome in widely in vasive Hurthle cell carcinoma, as does extrathyroidal extension.