Imaging Pearls ❯ Liver ❯ FNH
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- “Focal nodular hyperplasia (FNH) is a benign lesion of hepatocytic hyperplasia that arises in a background of normal or nearly normal liver. Histologically and radiologically identical lesions in a background of an abnormal liver are called FNH-like lesions. Although FNH is most common in young women, FNH-like lesions are seen in myriad populations with liver abnormalities who share an underlying cause of hepatic vascular disturbance, including those with abnormalities of hepatic inflow and outflow and hepatic microvascular disturbances.”
Focal Nodular Hyperplasia and Focal Nodular Hyperplasia–like Lesions
Jordan D. LeGout et al
RadioGraphics 2022; 42:1043–1061 - “FNH is the second most common benign liver lesion after hemangioma, representing 8% of primary hepatic lesions. It has an incidence of 0.9%, is much more common in women than in men (8:1), and is most commonly diagnosed in the 3rd to 5th decades of life. FNH is usually a singular lesion, but there may be multiple lesions in 20% of cases.”
Focal Nodular Hyperplasia and Focal Nodular Hyperplasia–like Lesions
Jordan D. LeGout et al
RadioGraphics 2022; 42:1043–1061 - “Histologically, FNH is hyperplastic growth of morphologically normal hepatocytes, with-out normal development of the portal tract. A central fibrovascular scar and radiating fibrous septa contain large malformed feeder arteries and branches. Ductular proliferation is charac-teristically present along the septal edges. Although the pathogenesis is not fully under-stood, most researchers agree that FNH forms as a hyperplastic response to abnormal hepatic blood flow .”
Focal Nodular Hyperplasia and Focal Nodular Hyperplasia–like Lesions
Jordan D. LeGout et al
RadioGraphics 2022; 42:1043–1061 - “Most cases of FNH are asymptomatic and incidental. FNH lesions have no malignant potential, and hemorrhage and rupture are rare, with only 10 reported cases in the literature . Consequently, asymptomatic FNH requires no treatment or imaging follow-up in patients with no known malignancy or underlying liver disease. FNH is rarely symptomatic when the lesion is large or secondary to mass effect. Surgery or local-regional therapy, most commonly transarterial bland embolization, are both effective for management of symptomatic FNH.”
Focal Nodular Hyperplasia and Focal Nodular Hyperplasia–like Lesions
Jordan D. LeGout et al
RadioGraphics 2022; 42:1043–1061 - Conditions Predisposing Patients to Formation of FNH-like Lesions Abnormalities
- Abnormalities of hepatic outflow
--- Budd-Chiari syndrome
--- Fontan-associated liver disease
--- other forms of cardiogenic congestive hepatopathy
- Abnormalities of hepatic inflow
--- Congenital absence of the portal vein
--- Cavernous transformation
--- Hereditary hemorrhagic telangiectasia
- Hepatic microvascular disturbances
--- Cirrhosis
--- Nodular regenerative hyperplasia
--- Chemotherapy induced - “Histologically, a central scar composed of fibrous and myxomatous elements is present in almost all cases of FNH but is visible in only approximately 60% of lesions with CT and in 80% of lesions with MRI. A large feeding artery may be visualized in the central scar but is best depicted on early angiographic images and may not be identified during the late hepatic arterial phase, when images of the liver are routinely ac-quired. At CT and MRI with extracellular contrast agents, the scar is hypoenhancing on arterial and portal venous phase images and shows delayed hyperenhancement at 2–5 minutes.”
Focal Nodular Hyperplasia and Focal Nodular Hyperplasia–like Lesions
Jordan D. LeGout et al
RadioGraphics 2022; 42:1043–1061 - “Most (85%) FNH lesions are smaller than 5 cm, and only a small percentage are larger than 10 cm. Although they were originally described as static, it is now known that 12%–15% of FNH lesions grow and approximately 9% regress over time. Growth may cause clinical uncertainty, but is not associated with patient symptoms or other adverse outcomes and should not be considered an indica-tion for surgical resection; however, referral to a tertiary care center could be considered to confirm the accuracy of the imaging diagnosis and to facilitate multidisciplinary management.”
Focal Nodular Hyperplasia and Focal Nodular Hyperplasia–like Lesions
Jordan D. LeGout et al
RadioGraphics 2022; 42:1043–1061 - “FNH-like lesion is the term applied to lesions that are macroscopically, microscopically, and immu-nohistochemically identical to FNH but occur in a background of abnormal liver. Myriad liver conditions predispose patients to formation of FNH-like lesions, all of which share a vascular disturbance as the inciting cause. Because they are histologically identical to FNH, FNH-like lesions carry no risk for malignant de-generation. Although they may create diagnostic confusion, they are otherwise typically clinically silent.”
Focal Nodular Hyperplasia and Focal Nodular Hyperplasia–like Lesions
Jordan D. LeGout et al
RadioGraphics 2022; 42:1043–1061
- Focal nodular hyperplasia (FNH) is the second most common tumor of the liver, surpassed in prevalence only by hepatic hemangioma. The incidence of FNH is estimated to be 3-5%, and it occurs most often in women in the third through fifth decades of life
- "CT depicted 124 tumors (mean diameter, 4.1 cm; range, 1–11 cm); 62 were small (≤3 cm). FNHs were hypervascular and hyperattenuating to liver on 106 of 106 arterial phase scans and were isoattenuating to liver on 82 of 89 delayed scans. Of the 124 tumors, 111 enhanced homogeneously, 109 had a smooth surface, 101 were subcapsular, 89 had ill-defined margins, and 62 had a central scar that was observed more often in large lesions (40 of 62 lesions) than in small lesions (22 of 62 lesions). FNHs less frequently exerted a mass effect (43 lesions), had vessels around or within the lesion (42 lesions), demonstrated exophytic growth (40 lesions), or showed a pseudocapsule (10 lesions). Only one FNH had calcification.”
Focal Nodular Hyperplasia: CT Findings with Emphasis on Multiphasic Helical CT in 78 Patients
Giuseppe Brancatelli, MD Michael P. Federle, MD Luigi Grazioli, MD et al.
Radiology 2001; 219:61–68 - "Of the 117 lesions seen on nonenhanced CT scans, the FNH was hypoattenuating to liver in 47 (40%), isoattenuating in 66 (57%), and hyperattenuating in four (3%). All four hyperattenuating lesions were in livers with abnormally low attenuating liver parenchyma due to hepatic steatosis or Budd-Chiari syndrome. Of the 106 lesions seen on HAP scans, the FNH was hyperattenuating to liver in all 106 (100%). Of the 124 lesions seen on the PVP scans, eight (6%) were hypoattenuating, 89 (72%) were isoattenuating, and 27 (22%) were hyperattenuating. Of the 61 lesions seen on 5-minute delay scans, four (7%) were hypoattenuating, 54 (88%) were isoattenuating, and three (5%) were hyperattenuating.”
Focal Nodular Hyperplasia: CT Findings with Emphasis on Multiphasic Helical CT in 78 Patients
Giuseppe Brancatelli, MD Michael P. Federle, MD Luigi Grazioli, MD et al.
Radiology 2001; 219:61–68 - "FNH is a benign neoplastic or tumorlike lesion of the liver that was rarely encountered by radiologists prior to the current practice of helical CT (or MR imaging) during the rapid bolus injection of contrast medium. The prevalence of FNH was found to be 0.9% in a study of 2,500 consecutive autopsies, indicating that, as imaging methods improve, FNH will be encountered frequently (4). Because FNH is benign and usually asymptomatic and because fine-needle aspiration cytology is likely to be nondiagnostic, confident and specific diagnosis of FNH is important to preclude invasive and expensive evaluation.”
Focal Nodular Hyperplasia: CT Findings with Emphasis on Multiphasic Helical CT in 78 Patients
Giuseppe Brancatelli, MD Michael P. Federle, MD Luigi Grazioli, MD et al.
Radiology 2001; 219:61–68 - "FNH is usually isoattenuating to liver on PVP and delayed phase scans, which accounts for the rarity of this diagnosis in the pre–helical CT era. Depending on factors including the rate of contrast medium injection, scanning delay, and circulation time, the upper half of the liver may be scanned during the late HAP– early PVP of imaging, accounting for the tendency to observe hyperattenuating FNH in the dome of the liver on PVP scans, on both helical and nonhelical scans.”
Focal Nodular Hyperplasia: CT Findings with Emphasis on Multiphasic Helical CT in 78 Patients
Giuseppe Brancatelli, MD Michael P. Federle, MD Luigi Grazioli, MD et al.
Radiology 2001; 219:61–68 - "A CT protocol designed to optimize detection and characterization of a focal hepatic mass would include the acquisition of nonenhanced sections and of images during the HAP, PVP, and ideally 5–10-minute delayed phase. On nonenhanced CT scans, FNH is usually isoattenuating (57% of our lesions) or slightly hypoattenuating (40%). FNH is only hyperattenuating to nonenhanced liver when there is hepatic steatosis or when the liver is otherwise abnormally decreased in attenuation. In some patients with hepatic steatosis, the FNH is still isoattenuating or hypoattenuating on nonenhanced CT; in rare cases, this may be due to fatty infiltration of the FNH itself.”
Focal Nodular Hyperplasia: CT Findings with Emphasis on Multiphasic Helical CT in 78 Patients
Giuseppe Brancatelli, MD Michael P. Federle, MD Luigi Grazioli, MD et al.
Radiology 2001; 219:61–68 - "FNH is a benign-appearing homogeneous mass with attenuation similar to that of normal liver on nonenhanced, PVP, and delayed phase scans; however, it enhances brightly and homogeneously on HAP scans. Lesions larger than 3 cm in diameter usually demonstrate a thin scar, and all FNH lesions typically have a smooth though ill-defined margin and are usually subcapsular. Exophytic growth, presence of a pseudocapsule, peritumoral vessels, and hyperattentuation to fatty liver should not mitigate against this diagnosis. When helical multiphasic CT demonstrates findings characteristic of FNH, further evaluation is often not necessary.”
Focal Nodular Hyperplasia: CT Findings with Emphasis on Multiphasic Helical CT in 78 Patients
Giuseppe Brancatelli, MD Michael P. Federle, MD Luigi Grazioli, MD et al.
Radiology 2001; 219:61–68 - “Focal nodular hyperplasia (FNH) is the second most common benign solid liver lesion after hemangioma, with a reported prevalence of 0.9% in the adult population and most lesions occurring in young patients. The male-to-female ratio of 1:8, and the characteristics of FNH regarding patient sex have been debated. Some authors have reported that FNHs developing in men were smaller and more often atypical, though a recent study has showed no difference in age of occurrence, size, and imaging features.”
Imaging of Hepatic Focal Nodular Hyperplasia: Pictorial Review and Diagnostic Strategy
Burgio MD et al.
Semin Ultrasound CT MRI 37:511-524 (2016) - “FNH is often an incidental finding at imaging in asymptomatic patients, and distinction between FNHs and other hypervascular focal liver lesions such as hepatocellular adenoma, hepatocellular carcinoma (HCC), and hypervascular metastases is critical to ensure proper management. Indeed, FNH is not associated with any malignant potential. Therefore, most confirmed FNHs are managed conservatively. Surgical approach is considered for rare sympto- matic lesions and when the diagnosis of hepatocellular adenoma or carcinoma cannot be ruled out.”
Imaging of Hepatic Focal Nodular Hyperplasia: Pictorial Review and Diagnostic Strategy
Burgio MD et al.
Semin Ultrasound CT MRI 37:511-524 (2016) - “Central scar in FNH corresponds to a collection of blood vessels, and bile ducts, surrounded by inflammatory cells and encased by a fibrous stroma. On CT, the scar is observed in approximately half of the lesions, whereas in MRI, it is seen in 80% of the lesions.The central scar is typically hypointense on precontrast T1-weighted MR images, hyperintense on T2-weighted MR images (78%-84%), and gradually enhances to become hyperintense on delayed phase contrast- enhanced T1-weighted MR images using extracellular contrast agents because of the accumulation of the contrast in the extracellular space of fibrotic tissue.”
Imaging of Hepatic Focal Nodular Hyperplasia: Pictorial Review and Diagnostic Strategy
Burgio MD et al.
Semin Ultrasound CT MRI 37:511-524 (2016) - “FNH may present as pedunculated lesion in approximately 9% of the cases. It is the second most common pedunculated lesion after hemangioma. Even if the connection with the liver is not clearly seen on imaging, CT and MRI characteristics of the lesion are identical to the classical intrahepatic pattern, usually allowing a confident diagnosis. Even though pedunculated lesions may be symptomatic, owing to tumoral compression of surrounding structures or lesion torsion, approximately 80% of these patients have no symptoms.”
Imaging of Hepatic Focal Nodular Hyperplasia: Pictorial Review and Diagnostic Strategy
Burgio MD et al.
Semin Ultrasound CT MRI 37:511-524 (2016) - “As stated earlier, a central scar is observed in approximately 65% of FNHs ➢3 cm and in 35% of FNHs <3 cm. Therefore, among all imaging features of FNH, absence of central scar is the most frequent “atypia.” Even if all other imaging features are present, the diagnosis of FNH cannot be reached if the central scar is absent.”
Imaging of Hepatic Focal Nodular Hyperplasia: Pictorial Review and Diagnostic Strategy
Burgio MD et al.
Semin Ultrasound CT MRI 37:511-524 (2016) - “Calcification is a rare finding in FNH and requires further documentation of benignity because other hypervascular lesions, such as fibrolamellar carcinoma or metastases frequently harbor calcifications. Caseiro-Alves et al have reported 5 FNH lesions with calcification in a series of 295 patients (1.4%). Calcification of FNH is usually solitary, small, and centrally located and should be differentiated from that observed in fibrolamellar HCC.”
Imaging of Hepatic Focal Nodular Hyperplasia: Pictorial Review and Diagnostic Strategy
Burgio MD et al.
Semin Ultrasound CT MRI 37:511-524 (2016)
- “FNH is a benign hypervascular tumor arising from the normal liver parenchyma. It occurs - FNH are a central scar, intratumoral centrifugal arteries from the center, and the presence of Kupffer cells and the proliferation of cholangiole, among others.
On contrast-enhanced CT, FNHs undergo marked enhancement during the arterial phase, becoming appreciably hyperattenuating relative to the hepatic parenchyma. Moreover, one or more large feeding hepatic arteries, small central and septal arteries, and early draining veins.”
Hypervascular Benign and Malignant Liver Tumors That Require Differentiation from Hepatocellular Carcinoma: Key Points of Imaging Diagnosis Takamichi Murakami* and Masakatsu Tsurusaki Liver Cancer. 2014 May; 3(2): 85–96.
- “Focal nodular hyperplasia (FNH) is the second most common benign solid liver lesion after hemangioma, with a reported prevalence of 0.9% in the adult population and most lesions occurring in young patients. The male-to-female ratio of 1:8, and the characteristics of FNH regarding patient sex have been debated. Some authors have reported that FNHs developing in men were smaller and more often atypical, though a recent study has showed no difference in age of occurrence, size, and imaging features.”
Imaging of Hepatic Focal Nodular Hyperplasia: Pictorial Review and Diagnostic Strategy Burgio MD et al. Semin Ultrasound CT MRI 37:511-524 (2016) - “FNH is often an incidental finding at imaging in asymptomatic patients, and distinction between FNHs and other hypervascular focal liver lesions such as hepatocellular adenoma, hepatocellular carcinoma (HCC), and hypervascular metastases is critical to ensure proper management. Indeed, FNH is not associated with any malignant potential.Therefore, most confirmed FNHs are managed conservatively. Surgical approach is considered for rare sympto- matic lesions and when the diagnosis of hepatocellular adenoma or carcinoma cannot be ruled out.”
Imaging of Hepatic Focal Nodular Hyperplasia: Pictorial Review and Diagnostic Strategy Burgio MD et al. Semin Ultrasound CT MRI 37:511-524 (2016) - “Central scar in FNH corresponds to a collection of
blood vessels, and bile ducts, surrounded by inflammatory cells and encased by a fibrous stroma. On CT, the scar is observed in approximately half of the lesions, whereas in MRI, it is seen in 80% of the lesions.The central scar is typically hypointense on precontrast T1-weighted MR images, hyperintense on T2-weighted MR images (78%-84%), and gradually enhances to become hyperintense on delayed phase contrast- enhanced T1-weighted MR images using extracellular contrast agents because of the accumulation of the contrast in the extracellular space of fibrotic tissue.”
Imaging of Hepatic Focal Nodular Hyperplasia: Pictorial Review and Diagnostic Strategy Burgio MD et al. Semin Ultrasound CT MRI 37:511-524 (2016) - “FNH may present as pedunculated lesion in approximately 9% of the cases. It is the second most common pedunculated lesion after hemangioma. Even if the connection with the liver is not clearly seen on imaging, CT and MRI characteristics of the lesion are identical to the classical intrahepatic pattern, usually allowing a confident diagnosis. Even though pedunculated lesions may be symptomatic, owing to tumoral compression of surrounding structures or lesion torsion, approximately 80% of these patients have no symptoms.”
Imaging of Hepatic Focal Nodular Hyperplasia: Pictorial Review and Diagnostic Strategy Burgio MD et al. Semin Ultrasound CT MRI 37:511-524 (2016) - “As stated earlier, a central scar is observed in approximately 65% of FNHs ➢3 cm and in 35% of FNHs <3 cm. Therefore, among all imaging features of FNH, absence of central scar is the most frequent “atypia.” Even if all other imaging features are present, the diagnosis of FNH cannot be reached if the central scar is absent.”
Imaging of Hepatic Focal Nodular Hyperplasia: Pictorial Review and Diagnostic Strategy Burgio MD et al. Semin Ultrasound CT MRI 37:511-524 (2016) - “Calcification is a rare finding in FNH and requires further documentation of benignity because other hypervascular lesions, such as fibrolamellar carcinoma or metastases frequently harbor calcifications. Caseiro-Alves et al have reported 5 FNH lesions with calcification in a series of 295 patients (1.4%). Calcification of FNH is usually solitary, small, and centrally located and should be differentiated from that observed in fibrolamellar HCC.”
Imaging of Hepatic Focal Nodular Hyperplasia: Pictorial Review and Diagnostic Strategy Burgio MD et al. Semin Ultrasound CT MRI 37:511-524 (2016)
- Focal Nodular Hyperplasia
- Female predominance (usually young)
- Composed of variable degrees of hepatocytes, bile ducts, and Kuppfer cells
- Will take up Tc-99m Sulfur Colloid
- Will take up Eovist
- Multiple in ¼ of cases - Focal Nodular Hyperplasia
- Blood supply via the hepatic artery
- Homogeneously hypervascular (to IVC level)
- “Flower morphology”
- Hypertrophied feeding vessel to center (without substantial neovascularity)
- Often invisible in the venous phase
- 50% demonstrate central scar (esp. when large)
- Scar can enhance on delayed images
- No capsule
- Focal Nodular Hyperplasia
1. Blood supply via the hepatic artery
2. Homogeneously hypervascular (to IVC level)
- “Flower morphology”
- Hypertrophied feeding vessel to center (without substantial neovascularity)
3. Often invisible in the venous phase
4. 50% demonstrate central scar (esp. when large)
- Scar can enhance on delayed images
5. No capsule
- “ The mean FNH attenuation level was lower than 50% of the mean aortic attenuation during the
arterial phase (115 vs 144 Hounsfield units) and also lower than the mean IVC attenuation in the
portal venous phase (142 vs 153 Hounsfield units).”
Dual-phase computed tomographic angiography of focal nodular hyperplasia: defining
predictable postcontrast attenuation levels relative to aorta and inferior vena cava
Johnson PT, Zaheer A, Anders R, Fishman EK
J Comput Assist Tomogr 2010 Sept-Oct;34(5):720-4 - “In this series of patients imaged with contrast-enhanced multidetector CT, most FNHs
demonstrated arterial attenuation levels lower than 50% of the aorta and/or portal venous
attenuation levels lower than or equal to those of the IVC.”
Dual-phase computed tomographic angiography of focal nodular hyperplasia: defining
predictable postcontrast attenuation levels relative to aorta and inferior vena cava
Johnson PT, Zaheer A, Anders R, Fishman EK
J Comput Assist Tomogr 2010 Sept-Oct;34(5):720-4 "In conclusion, this investigation confirmed the clinical observation that during the arterial phase, FNH demonstrates mild hyperenhancement, with attenuation usually less than 50% of the aorta. During the portal venous phase, the attenuation of FNH rarely exceeds that of the IVC."
Dual Phase CT Angiography of Focal Nodular Hyperplasia: Defining Predictable Post-Contrast Attenuation Levels Relative to the Aorta and Inferior Vena Cava
Johnson PT, Zaheer A, Anders R, Fishman EK
J Comput Assist Tomogr (in press) 2010"The mean maximum diameter of the 19 masses was 46 mm (range 8 to 133 mm). Location was left lobe in 10 (5 lateral segment, 4 medial and one involving both segments), right lobe in 8 (posterior segment in 6, anterior in 2) and caudate in 1. The majority (14/19, 74%) were homogeneous in appearance, with smooth contour (13/19, 68%), no septations (19/19, 100%) and absence of a pseudocapsule (18/19, 95%). A central scar was identified in less than half (8/19, 42%)."
Dual Phase CT Angiography of Focal Nodular Hyperplasia: Defining Predictable Post-Contrast Attenuation Levels Relative to the Aorta and Inferior Vena Cava
Johnson PT, Zaheer A, Anders R, Fishman EK
J Comput Assist Tomogr (in press) 2010"Mean FNH attenuation was less than 50% of mean aorta during arterial phase (115 vs. 144 HU, respectively) and also less than mean IVC in portal venous phase (142 vs. 153 HU, respectively). Across cases, FNH arterial phase attenuation was < 50% of aorta in 74% (14/19). Portal venous attenuation of FNH was = IVC in 80% (12/15). One of the 2 enhancement patterns was present in 100% (15/15) of cases."
Dual Phase CT Angiography of Focal Nodular Hyperplasia: Defining Predictable Post-Contrast Attenuation Levels Relative to the Aorta and Inferior Vena Cava
Johnson PT, Zaheer A, Anders R, Fishman EK
J Comput Assist Tomogr (in press) 2010- Focal Nodular Hyperplasia: CT Findings
- Non contrast CT: isoattenuating or hyperattenuating
- Arterial phase CT: hypervascular but homogeneous with large feeding artery
- Venous phase CT: isodense to remaining liver