[Hürthle cell tumor of the thyroid gland. Analysis of a series of 33 cases].

Hurthle cell or oxyphil cell tumours of the thyroid, which consist of large cells with eosinophilic granular cytoplasm, rich in mitochondria, have given rise to much controversy in recent years. Difficulty in histological diagnosis (benign or malignant), unexpected evolution, and the possibility of very late recurrence and metastasis occurring in cases which were previously labelled benign, characterise these ambiguous tumours. Their malignant forms are most often classified with vesicular cancers of the thyroid. They differ from the latter by the frequent presence of lymphatic metastases, the lack of effect of I 131 on distant metastases and their poorer prognosis. The experience of the authors is based upon a series of 33 cases of Hurthle cell tumours of the thyroid treated surgically (27 benign, 6 malignant), with a mean age of 44 years for benign lesions and 50 years for cancers (range 17 to 69 years) showing a clear female predominance (66% of cases). They most often presented clinically as a cold thyroid nodule which tended to be larger in the case of cancers (5 out of 6 cases had a diameter of more than 5 cm). The limits of resection were most often dictated by the results of per-operative frozen section: total lobectomy + isthmectomy for benign tumours and total thyroidectomy if macroscopic or histological signs of malignancy were present (spread beyond the capsule, vascular invasion, lymphatic metastases), with cervical node clearance if N+. The 27 cases who underwent surgery for benign tumours have survived (1 single local recurrence after 7 years, without any malignant progression and a median survival of 7 years). No deaths have occurred among the 6 cases of malignant tumours (follow-up ranging from 1 to 9 years, median 5.4 years) but a present metastases. A study of the series published in the literature confirms the difficulty with diagnosis in terms of the benign or malignant nature of the tumours. It also stresses the justification for relatively aggressive surgery on the thyroid parenchyma and the need for a very long period of locoregional and general surveillance in order to assess the results of treatment. Survival rates for malignant forms range from 60 to 65% at 10 years and from 25 to 47% at 15 years.