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Hashimoto's thyroiditis (HT) seems to have favourable prognostic impact on papillary thyroid cancer (PTC), but data were obtained analysing all disease stages. Given that HT-related microenvironment involves solely the thyroid, we aimed to assess the relationship between HT, as detected through pathological assessment, and outcome in intrathyroidal PTC. This was a multicentre, retrospective, observational study including 301 PTC with no evidence of extrathyroidal disease. Primary study endpoint was the rate of clinical remission. Auxiliary endpoint was recurrence-free survival (RFS). HT was detected in 42.5% of the cohort and was associated to female gender, smaller tumour size, lower rate of aggressive PTC variants and less frequent post-surgery radio-iodine administration. HT showed relationship with significantly higher rate of clinical remission ( < 0.001, OR 4, 95% CI 1.78-8.94). PTCs with concomitant HT had significantly longer RFS, as compared with non-HT tumours ( = 0.004). After adjustment for other parameters affecting disease outcome at univariate analysis (age at diagnosis, histology, tumour size and multifocality), prognostic effect of HT remained significant ( = 0.006, OR 3.28, 95% CI 1.39-7.72). To verify whether HT could optimise the identification of PTCs with unfavourable outcome, we assessed the accuracy of 'non-HT status' as negative prognostic marker, demonstrating poor capability of identifying patients not maintaining clinical remission until final follow-up (probability of no clinical remission in PTCs without HT: 21.05%, 95% CI 15.20-27.93). In conclusion, our data show that HT represents an independent prognostic parameter in intrathyroidal PTC, but cannot improve prognostic specificity.

The most appropriate surgical management of "follicular neoplasm/suspicious for follicular neoplasm" lesions (FN), considering their low definitive malignancy rate and the limited predictive power of preoperative clinic-diagnostic factors, is still controversial. On behalf of the Italian Association of Endocrine Surgery Units (U.E.C. CLUB), we collected and analyzed the experience of 26 endocrine centers by computerized questionnaire. 1379 patients, surgically treated after a FN diagnosis from January 2012 and December 2103, were evaluated. Histological features, surgical complications, and medium-term outcomes were reported. Total thyroidectomy (TT) was performed in 1055/1379 patients (76.5 %), while hemithyroidectomy (HT) was carried out in 324/1379 cases (23.5 %). Malignancy rate was higher in TT than in HT groups (36.4 vs. 26.2 %), whereas the rates of transient and definitive hypoparathyroidism following TT were higher than after HT. Consensual thyroiditis (16.8 vs. 9.9 %) and patient age (50.9 vs. 47.9 %) also differed between groups. A cytological FN diagnosis was associated to a not negligible malignancy rate (469/1379 patients; 34 %), that was higher in TT than in HT groups. However, a lower morbidity rate was observed in HT, which should be considered the standard of care in solitary lesions in absence of specific risk factors. Malignancy could not be preoperatively assessed and clinical decision-making is still controversial. Further efforts should be spent to more accurately preoperatively classify FN thyroid nodules.

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