Carcinoma papilífero da tireóide: estudo comparativo entre os casos usuais e aqueles associados à tireoidite autoimune / Papillary carcinoma of the thyroid: a comparison of typical cases with those associated autoimmune thyroiditis

RESUMO

Os nódulos de tireóide são frequentes no mundo todo, principalmente entre as mulheres. A preocupação maior no seu estudo é afastar a presença de neoplasia maligna, que corresponde a aproximadamente 10% de todos os casos. Alguns procedimentos médicos têm sido usados para se chegar ao diagnóstico pré-operatório dos nódulos tireoideanos, dentre os quais a cintilografia, a ultrassonografia e, mais recentemente, a punção aspirativa com agulha fina... Na tentativa de colaborar para o esclarecimento desse tema, estudamos 102 amostras de tireóide arquivadas no banco de tumores do Hospital AC Camargo, formando com elas dois grupos de pacientes, um com carcinoma e tireoidite (70 pacientes) e outro, somente com carcinoma (32 pacientes). Tendo em vista a importância da caracterização objetiva do fenômeno inflamatório, subclassificamos, por parâmetros histológicos, a tireoidite em leve, moderada e intensa. Foi realizado estudo imunoistoquímico para avaliação de 16 proteínas relacionadas à presença de células indiferenciadas (p63), à via das MAPKs (Ras, AKT-1e ERK1/2), às moléculas de adesão (E-caderina e CD44), à ativação da via de sinalização Wnt (beta-catenina), à via do receptor de morte (Fas-L e caspase 8), às moléculas ligadas à indução de interleucinas (iNOS e COX-2), aos fatores de crescimento e diferenciação celulares (galectina 3 e VEGF) e aos índices de proliferação celular e apoptose (Ki-67, caspase 3 clivada e Fas). Além disso, fizemos a pesquisa da mutação V600E do gene BRAF por pirossequenciamento e a pesquisa dos rearranjos cromossômicos RET/PTC1 e RET/PTC3 por RT-PCR. Os resultados evidenciaram diferenças estatisticamente significativas na expressão de Ras, ERK1/2, CD44, COX-2 e Fas entre os grupos com e sem tireoidite. Essas diferenças também validaram a subclassificação histológica para a intensidade da tireoidite, ao demonstrar que quanto mais intensa ela se apresentou, maior foi a expressão imunoistoquímica dessas proteínas.

ABSTRACT

Thyroid nodules are common throughout the world, mainly in women. The principal focus of their study is to exclude the possibility of a malignant neoplasm, which is found in approximately 10% of all cases. Various medical procedures, such as scintillography, ultrasonography, and, more recently, fine needle aspiration biopsy are used pre-operatively to diagnose thyroid nodules. However, the definitive diagnosis is still the pathologic diagnosis, often preceded by examination of multiple frozen sections. One of the limiting factors of this method is the presence of autoimmune thyroiditis, as the morphological tissue alterations associated with this inflammation cause problems in the macroscopic and microscopic evaluation of the tissue. Not only during the frozen section analysis, but also during the definitive evaluation, the association between thyroiditis and papillary carcinoma is a challenge, as there is still no consensus about the nature of this association. In an attempt to help clarify this situation, we studied samples of thyroid tissue from 102 patients, collected from the archives of the Tumor Bank of the AC Camargo Hospital, divided into two groups; the first group consisted of 70 patients with both carcinoma and thyroiditis, while the second group of 32 patients had only carcinoma. Due to the importance of an objective characterization of the inflammatory process, specifically in this research, histological parameters were used to sub classify the thyroiditis as mild, moderate or severe. We used immunihistochemical methods to study 16 proteins related to: the presence of undifferentiated cells (p63); the MAPK pathway (Ras, AKT-1 and ERK1/2); adhesion molecules (E-caderin and CD44); the Wnt signal activation pathway (beta-catenin); the death receptor pathway (Fas-L and caspase 8); molecules associated with induction of interleukins (iNOS and COX-2); factors of growth and cellular differentiation (Galactin 3 and VEGF); and indices of cellular proliferation and apoptosis (Ki67, activated caspase 3 and Fas). As well, we used pyrosequencing to study the V600E mutation of the BRAF gene, and RT-PCR to evaluate rearrangements of chromosomes RET/PTC1 and RET/PTC3. Our results showed statistically significant differences between the groups with and without thyroiditis in the expression of Ras, ERK 1/2, CD44, COX-2 and Fas. These results also validated the histological sub classification used to grade the intensity of the thyroiditis; the more intense the thyroiditis, the greater was the immunihistochemical expression of these proteins.