The different morphologies of urachal adenocarcinoma do not discriminate genomically by micro-RNA expression profiling

Urachal adenocarcinoma has several morphologic presentations that include mucinous, enteric, signet ring cell, and not otherwise specified. Mixtures of these morphologies can occur, and percentage cut-offs are used for classification. The clinical significance of these morphologic types is currently unknown, and genetic analysis that could elucidate possible intertumoral differences has not been performed. In this study, we analyzed the micro-RNA expression profiles of 12 urachal adenocarcinomas classified using strict morphologic criteria (3 pure enteric, 3 pure mucinous, 2 signet ring cell [both 90% signet ring cell], 2 pure not otherwise specified, and 2 mixed cell types). Of 598 unique human micro-RNAs, 333 were expressed in more than 50% of the samples. Hierarchal clustering showed no distinct patterns in the genetic profiles of the morphologic types. However, there were individual micro-RNA differences when the different types were compared individually or grouped together, either by intracellular mucin production or by grouping enteric and signet ring cell together. In the later group, 13 messenger RNA species were differentially expressed (adjusted P value of ?.05). However, these micro-RNA differences were small, suggesting more biologic similarity than differences among these entities. Thus, this study suggests that the different morphological subtypes may represent patterns of differentiation or a continuum of a single biological tumor type rather than several distinct types that arose from the urachal remnant epithelium. This finding, if further validated in larger studies, may have implications in future clinical therapeutic trials for urachal adenocarcinoma with regard to patient grouping and choice of therapy.

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