RESUMEN
The differentiation between hereditary and sporadic microsatellite-unstable (MSI-H) colorectal cancer is a crucial step in Lynch syndrome diagnostics. Within MSI-H colorectal cancers, the BRAF V600E mutation is strongly associated with sporadic origin. Here, we asked whether BRAF V600E-specific immunohistochemistry (clone VE1) is helpful in separating sporadic from Lynch syndrome-associated MSI-H colorectal cancers. To that end, we performed VE1 immunohistochemistry and BRAF sequencing in a series of 91 MSI-H colorectal cancer specimens from patients tested for Lynch syndrome. Concordance of VE1 immunohistochemistry and molecular BRAF mutation status was observed in 90 of 91 (98.9%) MSI-H samples. All 11 tumors classified as BRAF V600E mutation-positive by Sanger sequencing were immunopositive, and 79 (98.8%) of 80 tumors classified as BRAF wild type showed negative staining. All VE1-positive tumors were MLH1- and PMS2-negative by immunohistochemistry. None of the tumors from mismatch repair (MMR) gene germline mutation carriers (n = 28) displayed positive VE1 staining, indicating that BRAF V600E mutation-specific immunostaining has a low risk of excluding Lynch syndrome patients from germline mutation analysis. In conclusion, implementation of VE1 immunohistochemistry was able to detect BRAF-mutated MSI-H colorectal cancers with a sensitivity of 100% and a specificity of 98.8%. Among MLH1-negative colorectal cancers, the rate of VE1-positive lesions was 21%, offering the exclusion of these patients from MMR germline testing. Therefore, we suggest the integration of VE1 immunohistochemistry into the diagnostic panel of Lynch syndrome.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales/genética , Neoplasias Colorrectales Hereditarias sin Poliposis/diagnóstico , Neoplasias Colorrectales Hereditarias sin Poliposis/genética , Inestabilidad de Microsatélites , Proteínas Nucleares/genética , Proteínas Proto-Oncogénicas B-raf/genética , Proteínas Adaptadoras Transductoras de Señales/metabolismo , Adulto , Anciano , Anciano de 80 o más Años , Secuencia de Bases , Reparación de la Incompatibilidad de ADN , Femenino , Mutación de Línea Germinal , Humanos , Inmunohistoquímica , Masculino , Persona de Mediana Edad , Homólogo 1 de la Proteína MutL , Proteínas Nucleares/metabolismo , Regiones Promotoras Genéticas , Análisis de Secuencia de ADNRESUMEN
Infantile and childhood hepatoblastoma (HB) occurs more frequently in children with hereditary predisposition to familial adenomatous polyposis (FAP) than in the general population. The occurrence of HB in two infant siblings is reported. The sister died of the disease. The brother survived the HB and was later diagnosed with familial adenomatous polyposis and advanced rectal cancer. He was found to carry a germline mutation of the APC gene. Presuming that the HB in the two siblings was the first manifestation of FAP we performed APC mutation analysis in DNA from archived tumour tissue of his sister and in blood samples of both parents. Surprisingly, the mutation was neither found in both parents, nor in the tissue samples of the sister. We outline the impact of this finding for genetic counselling and review the literature on FAP and HB.
Asunto(s)
Proteína de la Poliposis Adenomatosa del Colon/genética , Poliposis Adenomatosa del Colon/genética , Hepatoblastoma/genética , Neoplasias Hepáticas/genética , Femenino , Mutación de Línea Germinal , Humanos , Lactante , Masculino , Persona de Mediana Edad , Linaje , HermanosRESUMEN
Germline deletions affecting the epithelial cell adhesion molecule (EPCAM) gene lead to silencing of MSH2 and cause Lynch syndrome. We have recently reported that lack of EPCAM expression occurs in many, but not all tumors from Lynch syndrome patients with EPCAM germline deletions. The differences in EPCAM expression were not related to the localization of EPCAM germline deletions. We therefore hypothesized that the type of the second somatic hit, which leads to MSH2 inactivation during tumor development, determines EPCAM expression in the tumor cells. To test this hypothesis and to evaluate whether lack of EPCAM expression can already be detected in Lynch syndrome-associated adenomas, we analyzed four carcinomas and two adenomas from EPCAM germline deletion carriers for EPCAM protein expression and allelic deletion status of the EPCAM gene region by multiplex ligation-dependent probe amplification. In four out of six tumors we observed lack of EPCAM expression accompanied by biallelic deletions affecting the EPCAM gene. In contrast, monoallelic retention of the EPCAM gene was observed in the remaining two tumors with retained EPCAM protein expression. These results demonstrate that EPCAM expression in tumors from EPCAM deletion carriers depends on the localization of the second somatic hit that inactivates MSH2. Moreover, we report lack of EPCAM protein expression in a colorectal adenoma, suggesting that EPCAM immunohistochemistry may detect EPCAM germline deletions already at a precancerous stage.
