|ECR 2019 / C-0923|
|One, No One and One Hundred Thousand: The Wide Spectrum of Hepatic Cystic lesions - Tips and Tricks for Differential Diagnosis|
Hepatic cystic lesions – defined as lesions with predominant near-water content – are commonly encountered in everyday practice. The differential diagnosis ranges from benign developmental to malignant lesions, whose prognosis and management is radically different.
An important first step for narrowing the differential diagnosis is to determine the presence or absence of complex features in cystic liver lesions.
Simple hepatic cystic lesions
are one of the commonest liver lesions and occur in in 2,5 % of the population. They are usually asymptomatic and more prevalent in women older than 50 years. Simple hepatic cysts can be solitary or multiple, with the latter being the more typical scenario.
It is currently thought that true hepatic cysts arise from hamartomatous tissue.
At histopathologic analysis, simple hepatic cyst:
-contain serous fluid;
-are lined by a nearly imperceptible wall consisting of cuboidal epithelium, identical to that of bile ducts;
-do not communicate with the biliary tree.
Fibropolycystic liver diseases (Fig1): due to abnormal embryologic development of the ductal plates.
Peribiliary cysts (Fig2): caused by obstruction of the neck of the periductal gland.
Complex hepatic cystic lesions
Biliary cystadenoma and biliary cystadenocarcinoma
Biliary cystadenoma are rare premalignant lesions, mainly occurring in middle-aged women. These lesions may degenerate into biliary cystadenocarcinoma and the differential diagnosis between the two entities is particularly challenging on imaging.
Symptoms: intermittent pain or biliary obstruction due mass effect of the lesion.
Histologically cystadenomas are characterized by ovarian-type stroma.
They arise mainly from the intrahepatic ducts and rarely from the extrahepatic ducts or gallbladder.
Hemorrhagic or complicated cysts
Symple cysts can rarely become complex as a result of hemorrhage or superinfection. The clinical manifestation of hemorrhage is severe acute abdominal pain, caused by the enlargement of the cyst and the subsequent compression of adjacent anatomical structures.
Although hemangiomas are the most common benign tumors of the liver, giant hemangiomas (> 6 cm) are rare.
They are histologically more heterogeneous than smaller hemangiomas and can presents areas of central necrosis/liquefaction.
Parasitic infection most commonly caused by Echinococcus granulosus.
Definitive hosts are dogs, intermediate hosts are sheep, while humans are accidental host, infected by the ingestion of food or water contaminated by dog feces containing the eggs of the parasite.
Hydatid disease continues to be a significant health problem in underdeveloped areas where animal husbandry is common but no veterinary control exists.
The liver is the most common site of involvement, followed by the lung.
At biochemical analysis there is usually eosinophilia. Echinococcus induces an antibody response, most commonly IgG mediated, even if in approximately 30–40% of patients, no antibodies of any kind are detectable.
Pyogenic abscess is the most common type. They can result from ascending cholangitis, hematogenous dissemination from a gastrointestinal infection via the portal vein, disseminated sepsis via the hepatic artery, or contiguous spread. Another route of bacterial liver seeding is direct inoculation, from either penetrating trauma or an invasive procedure.
Due to either necrosis of hypervascular metastases secondary to rapid growth beyond the vascular supply (i.e. neuroendocrine tumor, melanoma, GIST and certain subtypes of lung and breast carcinoma) or abundant mucin production by acinar structures and glandular tissues (i.e. mucinous adenocarcinoma, such as colorectal or ovarian carcinoma).
Treated liver metastases may also appear as multilocular cystic lesions (e.g. GIST after treatment with imatinib) because of devascularization and increase in the necrotic component.