The most important systemic etiological factors for portal thrombosis are the thrombophilic conditions associated with myeloproliferative disorders (MPDs), either clinically manifest or so-called 'occult'. Latest studies have revealed a strong association between MPDs and a somatic point mutation (V617F) of the tyrosine kinase Janus kinase2. The 'pseudo-cholangiocarcinoma sign' is a well described radiological finding related to portal cavernoma. We describe the case of a 48-year-old man, presenting with cavernomatous transformation of an extrahepatic thrombotic obstruction of the portal vein mimicking a neoplastic mass of the hepatic hilum, who did not present any other cause for thrombosis except for the V617F Janus kinase2 mutation, suggesting an underlying MPD.