Biliary cystadenoma is a rare benign intrahepatic tumor that arises from the biliary system and is primarily diagnosed in middle-aged women. The clinical presentation includes abdominal pain, nausea, vomiting, and a palpable mass accompanied by jaundice. Symptoms may last for months or years before the diagnosis is made, which increases the risk for rare, but possible malignant transformation. Computed tomography (CT), magnetic resonance imaging (MR), and magnetic resonance cholangiopancreatography (MRCP) are recommended imaging studies.
Biliary cystadenoma is a cystic (either unilocular or multilocular) intrahepatic lesion that is considered to be a rare entity in clinical practice   . The tumor originates in the bile ducts, with the right lobe identified as the principal location in more than half of all cases  . However, extrahepatic location (the cystic, common hepatic, and bile ducts) has been documented in a small number of patients  . The exact pathogenesis model remains unknown; for some reason, biliary cystadenomas are mainly encountered in middle-aged women    . The potential for malignant transformation of biliary cystadenoma is low , but a delay in diagnosis (signs and symptoms can be present up to several years) is perhaps one of the main factors for a poorer prognosis, implying that early recognition is essential . The clinical presentation starts with symptoms such as abdominal pain that is often chronic in nature and a palpable mass in the right upper quadrant that persists for weeks, months, or even years    . Anorexia, nausea, vomiting, and either weight gain or weight loss are other important symptoms  . At some point, biliary tract obstruction leads to jaundice   .
The differential diagnosis of biliary cystadenoma is very broad, as hydatid cysts, liver abscesses, other malignant or benign tumors (including its malignant form - biliary cystadenocarcinoma), as well as hemorrhagic cysts, may have a similar clinical and radiologic presentation . For this reason, a meticulous workup should start with a carefully obtained patient history that will assess the course and progression of symptoms, as well as their duration. The physical examination can be a crucial component if a mass is detected during abdominal inspection and palpation. As soon as sufficient evidence suggests a hepatic lesion, imaging studies need to be employed. Abdominal ultrasonography is a useful first-line procedure that is able to reveal typical findings of a biliary cystadenoma - a unilocular or multilocular cyst . More advanced studies, however, are necessary in order to strengthen the diagnosis. Computed tomography (CT) shows a cystic lesion sharply delineated by a thick capsule made of fibrous tissue with internal septation (calcifications may also be present)     , but the introduction of magnetic resonance imaging (MRI, particularly gadolinium-enhanced), and especially magnetic resonance cholangiopancreatography (MRCP) has greatly improved the overall diagnosis rate of many lesions, including biliary cystadenoma   . These two procedures are the gold standard and should be used whenever possible, showing a homogeneously low intensity on T1-weighted images and very high signal intensity on T2-weighted images  .