Hashimoto's thyroiditis shares features with early papillary thyroid carcinoma

Abstract

Neoplastic transformation is a multistep process that results in a continuous spectrum from the normal (physiological) state to a fully established neoplasm. The gold standard for diagnosis of papillary thyroid carcinoma is conventional histology, the essential element being the characteristic nuclear features, regardless of whether papillary structures are present or not. However, other criteria are being used increasingly in the diagnosis of neoplasms, including immunohistochemical staining and molecular profile. The RET/PTC gene rearrangement is highly specific for papillary thyroid carcinoma and is associated with the characteristic nuclear features seen in papillary thyroid carcinoma. There is an overlap in the morphological features, immunohistochemical staining pattern, and most importantly, molecular profile between papillary thyroid carcinoma and Hashimoto's thyroiditis. Although considered a 'benign' condition, Hashimoto's thyroiditis almost always harbours a genetic rearrangement that is strongly associated with and is highly specific for papillary thyroid carcinoma. Submicroscopic foci of papillary thyroid carcinoma must be present in Hashimoto's thyroiditis, although the clinical behaviour is still benign. Further studies are required to predict which foci will progress to papillary thyroid carcinoma.

Is Hashimoto's Thyroiditis a Risk Factor for Papillary Thyroid Cancer?

“…[14] Arif, et al also supported this hypothesis, demonstrating both diseases have similar immunohistochemical staining, morphological features and molecular profile in regards to the RET/PTC gene rearrangement. [15] In addition, Unger, et al found expression of p63 in Hashimoto's patients with papillary thyroid cancer. [16] This was further examined by Burstein, et al who proposed the two diseases are both initiated by pluripotent p63-positive stem cell remnants.…”

Carcinoma papilífero da tireoide associado à tireoidite de Hashimoto: frequência e aspectos histopatológicos

“…Há diversos estudos tentando explicar a associação, por exemplo, pela expressão dos oncogenes RET/PTC-1 e RET/PTC-3 em pacientes com TH (31) , hipótese confirmada pela demonstração de que ambas as doenças têm imunofenotipagem, aspectos morfológicos e perfil molecular semelhantes quanto ao rearranjo do gene RET/PTC (1) . Além disso, foi demonstrada a expressão do p63 em THs associadas a CP da tireoide (29) , o que levou à proposição de que as duas doenças eram iniciadas por remanescentes pluripotentes de células tronco p63 positivas (3) .…”

Concomitância da tireoidite de Hashimoto e o carcinoma diferenciado da tireóide

“…O melhor método para o diagnóstico do carcinoma papilar está relacionado com o rearranjamento RET/PTC. Rearranjamentos do RET levam a uma expressão gênica, isto ocorre em aproximadamente 50% dos carcinomas papilares 20 . Porém, a tireoidite auto-imune e o carcinoma papilar da tireóide se misturam quanto à morfologia, modelo imunohistoquímico e perfil molecular.…”

“…Porém, a tireoidite auto-imune e o carcinoma papilar da tireóide se misturam quanto à morfologia, modelo imunohistoquímico e perfil molecular. Mesmo sendo considerada uma condição benigna a tireoidite auto-imune pode evidenciar rearranjamento do RET/PTC 20 . Outra característica interessante é a detecção freqüente do p63 em tireoidite auto-imune e carcinoma tireoidiano em contraste com a sua detecção incomum nos pacientes com outras neoplasias e na doença de Graves.…”