RESUMO
OBJECTIVE: To better define the clinical manifestations, radiologic imaging and the surgical management of cervical thymic lesions in children. STUDY DESIGN: Multi-center retrospective case review. METHODS: The charts of all children with pathologically confirmed thymic lesions at six children's hospitals (1990-2002) were reviewed for demographics, physical findings, X-ray findings, operative outcomes and pathology. RESULTS: There were a total of 15 children, 2 of whom had ectopic cervical thymus and 13 who had thymic cysts. They ranged in age from 1 month to 18 years. Thymic lesions were more common in males. Ectopic cervical thymus was best defined by MRI whereas thymic cyst had a more consistent appearance on CT. All children had successful surgical resection with no recorded complications or recurrences. CONCLUSIONS: Cervical thymic lesions are rare. Ectopic cervical thymus tends to be found primarily in infants whereas thymic cysts occur in a wider age range. Radiologic imaging is important but is not histologically specific. Definitive diagnosis and cure requires complete surgical excision.
Assuntos
Coristoma/patologia , Cisto Mediastínico/patologia , Doenças da Coluna Vertebral/patologia , Timo , Criança , Coristoma/cirurgia , Diagnóstico Diferencial , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino , Cisto Mediastínico/cirurgia , Pescoço , Estudos Retrospectivos , Doenças da Coluna Vertebral/cirurgiaRESUMO
The cytosine methyltransferases (MTases) M. HhaI and M. HpaII bind substrates in which the target cytosine is replaced by uracil or thymine, i.e. DNA containing a U:G or a T:G mismatch. We have extended this observation to the EcoRII MTase (M. EcoRII) and determined the apparent Kd for binding. Using a genetic assay we have also tested the possibility that MTase binding to U:G mismatches may interfere with repair of the mismatches and promote C:G to T:A mutations. We have compared two mutants of M. EcoRII that are defective for catalysis by the wild-type enzyme for their ability to bind DNA containing U:G or T:G mismatches and for their ability to promote C to T mutations. We find that although all three proteins are able to bind DNAs with mismatches, only the wild-type enzyme promotes C:G to T:A mutations in vivo. Therefore, the ability of M. EcoRII to bind U:G mismatched duplexes is not sufficient for their mutagenic action in cells.
