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Abstract. The tall cell variant (TCV) of papillary thyroid carcinoma (PTC) is characterized by tall columnar cells with a height of at least three times their width. TCV usually presents at an older age, has a larger size and exhibits more extrathyroidal extension and metastases than classical PTC. The current study compared TCV with the classical and follicular variants (CaFVs) of PTC to determine if, irrespective of the age at diagnosis and tumor size, TCV is more aggressive than its classical and follicular counterparts. A total of 16 (3.66%) patients with TCV were identified in a series of 437 patients with PTC from the Clinical University Hospital (Santiago de Compostela, Spain) between 1990 and 2010. The patient clinicopathological features and B-Raf proto-oncogene (BRAF) V600E mutational status were compared with 34 cases of CaFVs of PTC matched for tumor size and patient age. The TCV series included 11 females and 5 males aged 15-74 years (median, 57 years). In total, 15 (93.8%) patients underwent total or near-total thyroidectomy, 1 underwent lobectomy and 5 (31.3%) underwent lymph node dissection. In the TCV series, the tumor size ranged from 5-45 mm (median, 19 mm ) and distant metastases (6.2% vs. 0.0%), as compared with the matched patient cohort. In conclusion, the TCV of PTC is frequently associated with BRAF V600E mutation and is more aggressive than the CaFVs of PTC, regardless of tumor size and patient age at diagnosis.

Given the high incidence and excellent prognosis of many papillary thyroid microcarcinomas, the Porto proposal uses the designation papillary microtumor (PMT) for papillary microcarcinomas (PMCs) without risk factors to minimize overtreatment and patients’ stress. To validate Porto proposal criteria, we examined a series of 190 PMC series, also studying sex hormone receptors and BRAF V600E mutation. Our updated Porto proposal (uPp) reclassifies as PMT incidental PMCs found at thyroidectomy lacking the following criteria: (a) detected under the age of 19 years; (b) with multiple tumors measuring >1 cm adding up all diameters; and (c) with aggressive morphologic features (extrathyroidal extension, angioinvasion, tall, and/or hobnail cells). PMCs not fulfilling uPp criteria were considered “true” PMCs. A total of 102 PMCs were subclassified as PMT, 88 as PMC, with no age or sex differences between subgroups. Total thyroidectomy and iodine-131 therapy were significantly more common in PMC. After a median follow-up of 9.6 years, lymph node metastases, distant metastases, and mortality were only found in the PMC subgroup. No subgroup differences were found in calcifications or desmoplasia. Expression of estrogen receptor-α and estrogen receptor-β, progesterone receptor, and androgen receptor was higher in PMC than in nontumorous thyroid tissue. BRAF mutations were detected in 44.7% of PMC, with no differences between subgroups. In surgical specimens, the uPp is a safe pathology tool to identify those PMC with extremely low malignant potential. This terminology could reduce psychological stress associated with cancer diagnosis, avoid overtreatment, and be incorporated into daily pathologic practice.

Objective: The present study was designed to investigate the dosedependent protective effect of L-carnitine (LC) on thyroid hormoneinduced oxidative stress in rat liver tissue. Materials and Methods:Twenty-one male Sprague Dawley rats were divided into four groups: control, hyperthyroidism, hyperthyroidism plus L-carnitine 100, and hyperthyroidism plus L-carnitine 500. Hyperthyroidism was induced in rats by injecting 250 μg of L-thyroxine/ kg body weight/day for twenty consecutive days. The activities of catalase (CAT), glutathione peroxidase (GPX) and myeloperoxidase (MPO) and the level of malondialdehyde (MDA) were measured in liver homogenates. Results:The liver CAT, GPX and MPO activities were significantly lower in the hyperthyroid rats than in the control group. Treating hyperthyroid rats with both low-dose (100 mg/kg) and high-dose (500 mg/kg) L-carnitine for 10 days resulted in a marked increase in the activities of the antioxidant enzymes in the liver tissue. Conclusion:The present study indicates that the low-dose L-carnitine application was sufficient to prevent L-thyroxine-induced oxidative stress in rat livers.Key Words: Catalase, glutathione peroxidase, L-carnitine, Liver, Malondialdehyde, Myeloperoxidase Özet Amaç: Bu çalışma rat karaciğer dokusunda tiroid hormonu ile uyarı-lan oksidatif stres üzerine L-karnitinin doza bağlı koruyucu etkilerini araştırmaktı. Gereç ve Yöntem:Yirmi bir erkek Sprague Dawley rat 4 gruba bö-lündü: Kontrol, hipertroidi, hipertiroidi + L-karnitine 100 ve hipertiroidi + L-karnitine 500. Hipertiroidi, yirmi gün boyunca ratlara 250 μg / kg dozunda L-Thyroxine enjeksiyonu uygulanarak oluşturuldu. Karaciğer homojenatlarında katalaz (CAT), glutatyon peroksidaz (GPX), myeloperoksidaz (MPO) aktiviteleri ve malondialdehit (MDA) düzeyleri ölçüldü. Bulgular:Kontrollerle karşılaştırıldığında hipertiroidili ratlarda karaciğer CAT, GPX ve MPO aktiviteleri belirgin olarak azaldı. 10 gün boyunca hem düşük doz (100 mg/kg) hem de yüksek doz (500 mg/ kg) L-karnitin uygulaması hipertiroidili ratlarda karaciğer antioksidan enzim aktivitelerinde belirgin bir artışa yol açtı.Sonuç: Bu çalışmanın sonuçları L-Tiroksin ile uyarılan rat karaciğerin-deki oksidatif stresi önlemek için düşük doz L-karnitin uygulamasının yeterli olduğunu göstermektedir.

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