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Metanephric adenoma is a rare tumor of the kidney. So far metanephric adenomas were considered to be benign, slowly growing and non-metastasizing tumors with an excellent prognosis. Only recently two cases of metastasized metanephric adenomas were published. Therefore, diagnostic work up, therapy and follow up of this tumor have to be reassessed. We report the case of a 42 year old male with metanephric adenoma. Current literature concerning metanephric adenoma is reviewed.

BackgroundAbelson interactor 1 (Abi1) is an important regulator of actin dynamics during cytoskeletal reorganization. In this study, our aim was to investigate the expression of Abi1 in colonic mucosa with and without inflammation, colonic polyps, colorectal carcinomas (CRC) and metastases as well as in CRC cell lines with respect to BRAF/KRAS mutation status and to find out whether introduction of KRAS mutation or stimulation with TNFalpha enhances Abi1 protein expression in CRC cells.Methodology/Principal FindingsWe immunohistochemically analyzed Abi1 protein expression in 126 tissue specimens from 95 patients and in 5 colorectal carcinoma cell lines with different mutation status by western immunoblotting. We found that Abi1 expression correlated positively with KRAS, but not BRAF mutation status in the examined tissue samples. Furthermore, Abi1 is overexpressed in inflammatory mucosa, sessile serrated polyps and adenomas, tubular adenomas, invasive CRC and CRC metastasis when compared to healthy mucosa and BRAF-mutated as well as KRAS wild-type hyperplastic polyps. Abi1 expression in carcinoma was independent of microsatellite stability of the tumor. Abi1 protein expression correlated with KRAS mutation in the analyzed CRC cell lines, and upregulation of Abi1 could be induced by TNFalpha treatment as well as transfection of wild-type CRC cells with mutant KRAS. The overexpression of Abi1 could be abolished by treatment with the PI3K-inhibitor Wortmannin after KRAS transfection.Conclusions/SignificanceOur results support a role for Abi1 as a downstream target of inflammatory response and adenomatous change as well as oncogenic KRAS mutation via PI3K, but not BRAF activation. Furthermore, they highlight a possible role for Abi1 as a marker for early KRAS mutation in hyperplastic polyps. Since the protein is a key player in actin dynamics, our data encourages further studies concerning the exact role of Abi1 in actin reorganization upon enhanced KRAS/PI3K signalling during colonic tumorigenesis.

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Warthin's tumour and its metaplastic (infarcted) variant both express CK 7, 8, 18, and 19, which are typical for columnar differentiation. Cytokeratins typical of squamous differentiation are absent from Warthin's tumour and its metaplastic variant, irrespective of the squamous morphology of the epithelium in metaplastic Warthin's tumour. The expression of CK 5/14 and 17, which are typical of regenerative cells, is restricted to basal cells in Warthin's tumour, but is expressed also in surface cells in metaplastic Warthin's tumour.