Background
Hemangiomas are the most common benign tumors affecting the liver [1] and usually discovered incidentally. They are mesenchymal in origin, usually solitary, and composed of masses of blood vessels that are atypical or irregular in arrangement and size. Typically, there are large vascular cavities surrounded by a simple layer of endothelial cells, supported by fibrous connective tissue. [2] The majority of these lesions are smaller than 5 cm in diameter. [2]
The etiology of these lesions remains unknown. Some authorities consider hemangiomas to be benign congenital hamartomas.
Given the frequency with which the diagnosis of hepatic hemangiomas is made, it is important that clinicians understand the natural history of these tumors, as well as their optimal monitoring and management.
Pathophysiology
Hepatic hemangiomas may result from abnormal angiogenesis. [3]
Some authors have reported that steroid therapy, [4] female sex hormones, [5] ;and pregnancy [6] could increase the size of an already existing hemangioma. A study that prospectively evaluated 94 women with hepatic hemangiomas (mean follow-up of 7.3 years; range, 1-17 years) demonstrated an increase in the size of the hemangiomas in 23% of the women who received hormonal therapy as opposed to 10% of control subjects (P = 0.05). [5] Hemangiomas have also been reported in pregnant women following ovarian stimulation therapy with clomiphene citrate and human chorionic gonadotropin. [7] That said, the focal liver lesion practice guideline of the American College of Gastroenterology (ACG) states: "There has been no clear causative link between hemangiomas and female sex hormones, and thus, it is not recommended to avoid OCP [oral contraceptive pills] or pregnancy in patients with hemangiomas." [8]
Three main histologic subtypes of hepatic hemagioma exist:
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Cavernous hemagioma
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Capillary hemagioma (also known as "flash-filling" hemangioma)
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Sclerosed hemangioma
Each of these lesions has a somewhat different appearance radiologically. [9] Cavernous hemangiomas are characterized by large vascular spaces. During a contrast magnetic resonance image (MRI) study, there is slow flow of radiologic contrast medium into the tumor. The tumors exhibit nodular peripheral enhancement, as well as progressive centripetal filling (progressing inward toward the center). Capillary hemangiomas, however, are chacterized by smaller vascular spaces. During contrast MRI, there is rapid flow of contrast material, resulting in early enhancement. [9] Typically, capillary hemangiomas are smaller than 2 cm in diameter. [10]
Cavernous hemangiomas can grow to sizes much larger than 4 cm in diameter, the size that typically defines a "giant hemangioma." Giant hemangiomas can be complicated by the rather uncommon Kasabach-Merritt syndrome, in which it is postulated that platelets become entrapped in the vascular spaces of the tumor. This, in turn, leads to consumptive coagulopathy and fibrinolysis. Intratumoral bleeding can occur, resulting in enlargement of the tumor. [11]
Sclerosed hemangiomas are at the other end of the histologic sprecturm. It is postulated that some cavernous hemangiomas will degenerate and undergo fibrous replacement, leading to the development of the relatively uncommon sclerosed hemangioma. [11] Like cavernous hemangiomas, sclerosed hemangiomas exhibit slow contrast enhancement on MRI. These lesions also exhibit peripheral nodular enhancement but are marked by very late homogeneous filling with contrast medium. [9]
Epidemiology
Prevalence
Autopsy series have reported the prevalence of hepatic hemangioma to range from 0.4% to as high as 20%. [12] The widespread use of noninvasive abdominal imaging modalities has led to increased detection of asymptomatic lesions. Large reviews of radiology databases have estimated a 2.5-5.1% prevalence of hepatic hemangiomas. [13, 14]
Sex- and age-related demographics
Women, especially women with a history of multiparity, are affected more often than men. The female-to-male ratio is 4-6:1.
Hepatic hemangiomas can occur at all ages, but most are diagnosed in individuals aged 30-50 years. Female patients often present at a younger age and with larger tumors.
Hepatic hemangiomas may be seen in infancy. They have also been detected prenatally in a growing fetus. [15, 16]
Prognosis
The vast majority of hepatic hemagiomas are asymptomatic. Malignant transformation has not been described. Overall, a patient with an hepatic hemangioma has an excellent prognosis.
Complications
The most common reason for a patient with hepatic hemangioma to undergo surgery is abdominal pain. Increasing tumoral size and intratumoral bleeding can cause progressive abdominal pain. Less commonly, surgery is performed to addresse the rare complications noted below.
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Kasabach-Merritt syndrome (see Pathophysiolgy)
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Rupture with resultant hemoperitoneum: This is a dreaded but rare complication of giant hemangiomas (ie, an hemangioma > 4 cm in diameter). Patients typically present with abdominal pain and circulatory shock. A literature review published by Donati et al identified only 46 cases of spontaneous rupture in the medical literature. [17] The mean size of the ruptured lesions was 11.2 cm (with a range of 1-38 cm). [17] In a retrospective study that assessed 2071 patients with a radiologic diagnosis of hepatic hemangioma over 7 years, 157 patients with a giant hemangioma were identified—five (3.2%) of whom experienced spontaneous rupture. [18] The affected patients all underwent succcessful treatment wtih surgery or emergent transarterial embolization.
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Compression of the bile ducts and nearby arteries and veins: In a case report, a patient presented with lower extremity edema caused by compression of the inferior vena cava by a caudate lobe tumor. [19]
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Gastric compression: Early satiety, nausea, and vomiting may occur when large lesions compress the stomach, producing gastric outlet obstruction.
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Hemobilia
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High-output congestive heart failure
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Hepatic Hemangiomas. Hemangioma of the liver as seen on ultrasonography. Image from Wikimedia Commons/James Heilman, MD (https://commons.wikimedia.org/wiki/File:Hemangiomaliver.PNG).
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Hepatic Hemangiomas. (a): Transverse sonogram of the left lobe of liver presenting a typical hyperechogenic hemangioma. (b) and (c): Two different hypoechogenic liver lesions suspected to be atypical hemangiomas, subsequently confirmed by computed tomography scanning. Image from BMC Gastroenterology (https://bmcgastroenterol.biomedcentral.com/articles/10.1186/1471-230X-11-43).
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Hepatic Hemangiomas. Moderately (a) and heavily (b) T2-weighted magnetic resonance images show typical bright lesions. Image from BMC Gastroenterology (https://bmcgastroenterol.biomedcentral.com/articles/10.1186/1471-230X-11-43).
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Hepatic Hemangiomas. (A) On plain computed tomography (CT) scan, an oval, low-density lesion with clear boundaries and central liquefactive necrosis is seen). (B) and (C): CT-enhanced scans show nodular enhancement at the edges of the lesion during the early arterial phase, and a higher density than the normal liver, appearing as the “fast out, slow in” sign. Image from PLoS One (https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0135158).
Tables
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