ABSTRACT
In the familial form of papillary thyroid cancer (PTC), two or more members of the same family have to be affected with PTC. Prevalence is around 5% of all PTC. We performed a clinical analysis in 79 relatives of 16 patients of 7 unrelated kindred with the diagnosis of familial papillary thyroid carcinoma (FPTC). The results were compared with a control group. Thyroid palpation and TSH and TPO-Ab assessment was carried out in the relatives without a diagnosed PTC. Additionally, molecular analysis was performed in the sixteen affected patients. Clinical screening of the 79 family members showed the presence of goiter in 22/79 (29 %). This frequency was much higher than that observed in the control group (8.7%), p < 0.001. Hypothyroidism was found in 4 of the relatives (5%) vs. 2.5% observed in the control group, p < 0.01, and anti-thyroid antibodies (TPO-Ab) were positive in 14% of the relative's group vs. 10 % in the control group, (p = NS). In the molecular analysis, only a protooncogene TRK rearrangement was observed in family # 6. In conclusion, we found a higher incidence of goiter and hypothyroidism in the relatives of patients with FPTC. Nevertheless, TPO-Ab frequency was not different. No molecular abnormalities were indicative of a specific pattern in this subset of patients with FPTC.
En la forma familiar del carcinoma papilar de tiroides (CPT), dos o más miembros de la misma familia deben presentar CPT. Esta entidad ocurre en aproximadamente el 5% de todos los CPT. En este estudio, realizamos una evaluación de 79 familiares de 16 pacientes con diagnóstico de carcinoma papilar familiar (CPF) provenientes de 7 familias diferentes. Los resultados se compararon con los hallados en un grupo control. Se realizó palpación tiroidea y medición de TSH y anticuerpos anti-tiroperoxidasa (TPO-Ab) en todos los familiares. Además, se llevó a cabo el análisis molecular en los 16 sujetos que presentaban el diagnóstico de CPF. La evaluación de los 79 familiares de estos pacientes demostró la presencia de bocio en 22/79 (29%). Esta frecuencia fue mucho mayor que la observada en el grupo control (8.7%), p < 0.001. Se diagnosticó hipotirodismo en 4 familiares (5%) vs. 2.5%, observado en el grupo control, p < 0.01, y los TPO-Ab fueron positivos en 14% de los familiares vs. 10% del grupo control, (p = ns). En el análisis molecular, solamente se halló un rearreglo del protoncogen TRK en una de las 7 familias con CPF. En conclusión, hallamos una elevada prevalencia de bocio e hipotiroidismo en los familiares de pacientes con CPT. Sin embargo, la frecuencia de autoinmunidad no fue diferente. No se hallaron alteraciones moleculares distintivas en estos pacientes con CPF.
Subject(s)
Adult , Female , Humans , Male , Middle Aged , Carcinoma, Papillary/complications , Goiter/etiology , Hypothyroidism/etiology , Thyroid Neoplasms/complications , Autoantibodies/blood , Case-Control Studies , Carcinoma, Papillary/genetics , Carcinoma, Papillary/immunology , Gene Rearrangement , Goiter/diagnosis , Hypothyroidism/diagnosis , Iodide Peroxidase/blood , Oncogene Proteins/genetics , Pedigree , Prevalence , Reverse Transcriptase Polymerase Chain Reaction , Thyroid Neoplasms/genetics , Thyroid Neoplasms/immunology , Thyrotropin/bloodABSTRACT
A 29 yrs-old patient was referred to our hospital due to generalized convulsions. She had hyperthyroidism treated with methimazole. Her MRI showed 4 metastatic lesions in the brain. She had a goiter with a "cold" nodule and a palpable ipsilateral lymph node. The FNAB disclosed a papillary thyroid carcinoma. Under 5 mg of MMI treatment, she had a subclinical hyperthyroidism and TRAb were 47.8 percent (n.v. < 10 percent). The CT scan also showed lung metastasis. She underwent a total thyroidectomy with a modified neck dissection and she received an accumulated radioiodine dose of 700 mCi during the following two years. She died from the consequences of multiple metastatic lesions. Studies were performed in DNA extracted from paraffin-embedded tissue from the tumor, the metastatic lymph node and the non-tumoral thyroid. The genetic analysis of tumoral DNA revealed point mutations in two different genes: the wild type CAA at codon 61 of N-RAS mutated to CAT, replacing glycine by histidine (G61H) and the normal GCC sequence at codon 623 of the TSHR gene was replaced by TCC, changing the alanine by serine (A623S). In the non-tumoral tissue no mutations were found. In vitro studies showed a constitutive activation of the TSHR. It is very probable that this activating mutation of the TSHR is unable to reach the end point of the PKA cascade in the tumoral tissue. One possibility that could explain this is the presence of a cross-signaling mechanism generating a deviation of the TSH receptor cascade to the more proliferative one involving the MAPKinase, giving perhaps a more aggressive behavior of this papillary thyroid cancer.
Paciente de 29 anos foi encaminhada ao Hospital de Clínicas por causa de convulsões generalizadas. Apresentava hipertiroidismo tratado com metimazol (MMI). A ressonância magnética mostrava quatro lesões metastáticas cerebrais. Possuía bócio com nódulo frio e linfonodo palpável ipsilateral. Usando 5 mg de MMI, a paciente apresentava hipertiroidismo subclínico e TRAb = 47,8 por cento (normal < 10 por cento). A tomografia computadorizada também mostrava metástases pulmonares. A paciente foi submetida a tiroidectomia total com dissecção cervical modificada e recebeu dose acumulada de radioiodo de 700 mCi durante o período de dois anos. Foi analisado o DNA extraído de tecido emblocado em parafina do tumor, do linfonodo metastático e de tecido tiroidiano não-tumoral. Foram encontradas mutações pontuais em dois genes: uma substituição do genótipo selvagem CAA no códon 61 de /N-RAS/ por CAT, substituindo a glicina pela histidina (G61H) e uma substituição da seqüência normal GCC no códon 623 do gene TSHR por TCC, trocando a alanina pela serina (A623S). Não foram encontradas mutações no tecido não-tumoral. Estudos in vitro mostraram ativação constitutiva de TSHR. Já que esta mutação ativadora de TSHR foi incapaz de atingir o final da cascata PKA no tecido tumoral, sugere-se que um mecanismo de cross-signaling possa explicar o desvio da cascata do receptor de TSH para outra mais proliferativa, envolvendo MAPKinase e levando ao comportamento mais agressivo deste câncer papilífero.