RESUMO
A case is presented of a 10-year-old female twin with a cystic liver mass that debuted as a painless epigastric mass. The lesion was excised by hepatectomy of segments II and III, confirming in the review of the cavity the presence of a common mesentery with cecocolonic malposition. The postoperative course was normal and clinical and echographic study of her twin sister disclosed no anomalies. The anatomopathologic study of the lesion revealed a tumor of difficult filiation that presented features of mesenchymal hamartoma together with others of biliary cystadenoma. The amount and nature of the stromal component, together with the patient's age at appearance, made us classify the case as mesenchymal hamartoma. The morphologic findings observed seem to support the histopathologetic theory of a congenital origin.
