hepatic adenoma
What is it?
This is a relatively rare benign formation of a hepatocellular tumor, which most often occurs in women of the third and fourth decades of life. The ratio of women to men is approximately 10 to 1. The occurrence of liver adenoma was associated with the use of oral contraceptives and was gradually reduced due to the introduction of tablets containing moderate amounts of estrogen into clinical practice. On the other hand, the appearance of adenomas in men is more often associated with the use of anabolic steroids.
The lesion is usually single, but there are cases of multiple localization and different sizes (from 3-4 to 20 cm).
From 25 to 50% of patients with adenomas complain of pain in the right upper quadrant of the abdomen or in the epigastric area, while another large percentage have no symptoms, and the diagnosis of adenoma occurs accidentally during X-ray examinations (ultrasound, CT, MRI) performed for other reasons.
Large lesions (> 5 cm) have a potential risk of rapture and spontaneous bleeding inside the lesion itself or in the abdominal cavity (intra-abdominal, resulting in hemoperitoneum). Spontaneous rupture is more common in male patients taking anabolic steroids. Even when combined with increased exposure to estrogen during pregnancy, liver adenomas are at risk of spontaneous hemorrhage or rupture. A complication rate (rupture or bleeding) of 25% to 42% is reported, with the majority of these cases occuring in tumors larger that 5 cm in diameter. In patients taking oral contraceptives, discontinuation of their use, which is always recommended, sumetimes reduces the size of the lesion, but this does not happen in all cases.
As described earlier, liver adenomas are benign formations, but the risk of malignant degeneration of hepatocarcinoma ranges from 5% to 11% and is more relevant for lesions larger than 5 cm in diameter. Recently, studies of specific genetic mutations have made it possible to more accurately identify lesions with a high risk of neoplastic transformation: in particular, a TCF1 gene mutation is rarely involved in cytological atypia or malignant changes, while a β-catenin mutation predisposes to the development of hepatocellular carcinoma.
How is it diagnosed?
The ultrasound appearance of hepatocellular adenomas varies, which often complicates the characterization and ultrasound diagnosis (in fact, the sensitivity of ultrasound by itself is from 30 to 70%). In CT, the most common aspect is hypodenal formation (darker than the surrounding liver) with moderate enhancement (contrast) in the arterial phase. Depending on the presence of necrotic tissue or intra-focal hemorrhage, a reduced or increased density may be detected in the focal lesion.
On MRI, they appear as hypo- or hyperintensive signals on a T1-weighted scan, whereas on T2 they range from isointensive to slightly hyperintensive. Contrast enhancement (gadolinium is the most commonly used contrast agent for MRI) is greatest during the arterial phase and dissolves rapidly in the venous phase. A distinctive feature is that the signal intensity decreases in the fat suppression phases due to the high lipid content in the adenoma itself.
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