Clinical course and features of thyroid oncocytic (Hurthle cell) cancer: Comparison with thyroid follicular cancer.

Introduction and objectives: Although, oncocytic (Hurthle cell) carcinoma (OTC) resembles to follicular thyroid carcinoma (FTC), they are different tumors derived from thyroid follicular cells. OTC comprises 3-5% of all differentiated thyroid carcinomas and has more aggressive behaviour than FTC. Clinicians discuss about the treatment and prognosis of OTC. We evaluated its clinicopathological features and clinical course.

Material and methods: We examined and followed up 169 patients with OTC (126 minimally invasive, 43 widely invasive) and 837 patients with FTC (640 minimally invasive, 197 widely invasive). OTC and FTC were compared according to prognostic variables, recurrence rate (Rec) and outcome. The predictor factors impacting on recurrence in OTC were also determined.

Results: There were statistically significant differences between OTC and FTC in age, sex, capsule invasion (CI), tumor size (TS), total administered [131I]NaI dose (TID), stimulated thyroglobulin (sTg), Rec and stage (p < 0.001, p = 0.032, p < 0.001, p < 0.001, p = 0.004, p = 0.026, p = 0.017, p = 0.044, respectively). Age, CI, extrathyroidal extension (ETE), TS, initial lymph node metastasis (ILNM), sTg and stage (p = 0.01, p = 0.016, p < 0.001, p < 0.001, p < 0.001, p < 0.001, p < 0.001, respectively) were the predictors for recurrence in OTC. Metastasis incidence was 19.5% for OTC and 12% for FTC. The cause of death was cancer in 25 patients with FTC (2.8%) and 11 patients with OTC (6.5%).

Conclusion: The prognosis of minimally invasive OTC is quite favorable. However the prognosis of widely invasive OTC is unfavorable. RAI may be administered to these tumors, but it is in vain to insist on RAI after the first adjuvant therapy if it does not respond.