1) The document discusses various benign hepatic tumors classified by their cell of origin into hepatocellular, cholangiocellular, or mesenchymal tumors. 2) It provides details on common tumor types such as focal nodular hyperplasia and hepatic adenoma. It notes focal nodular hyperplasia typically appears as a solitary lesion in young females while hepatic adenoma has a higher risk of bleeding and transforming to HCC. 3) Imaging features of many tumors are described, including the typical arterial phase enhancement of focal nodular hyperplasia on CT/MRI and the risk of hemorrhage seen within hepatic adenomas.

1. Benign Hepatic
Tumors

2. Introduction
Common benign hepatic tumors may pose a diagnostic dilemma
when they manifest with atypical imaging features
Benign liver tumors are classified according to their cell of origin into
tumors of hepatocellular, cholangiocellular, or mesenchymal origin.

3. Benign Hepatic Tumors of Hepatocellular Origin
Adenoma
Focal Nodular Hyperplasia
Hepatocellular Nodules in Cirrhosis
Nodular Regenerative Hyperplasia

4. Benign Hepatic Tumors of Cholangiocellular
Origin
Hepatic Cyst
Biliary Hamartomas
Peribiliary Cyst
Biliary Cystadenoma
Caroli Disease
Biliary Papillomatosis

5. Benign Hepatic Tumors of
Mesenchymal Origin
Cavernous Hemangioma
Focal Fat
Angiomyolipoma
Lipoma
Peliosis Hepatis
Infammatory Pseudotumor

6. Adenoma
Rare
Histopathologic analysis, hepatic adenomas contain well-differentiated
hepatocytes lacking bile ducts or portal triads. Kupffer cells may rarely
Adenomas are solitary (80%) and typically occur in female patients (90%)
Predisposing factors - oral contraceptive use in female patients,
anabolic steroid use in male patients, and glycogen storage disease.
Patients with type IA glycogen storage disease, or von Gierke
disease→ multiple hepatic adenomas beginning at a young age
→rarely degenerate into HCC

7. Richly vascular tumor which frequently contains hemorrhage and
necrosis
Pseudocapsule derived from compressed/collapsed hepatic
parenchyma
Adenomas have variable lipid content ranging from
microscopic fat (detected in up to 77% with chemical shift MR) to
macroscopic fat (detected at CT in up 7%)

10. Complications related to hepatic adenomas include the risk of
spontaneous hemorrhage and rare progression to HCC. Therefore,
surgical resection is generally advised.

11. Hepatic adenomatosis has been defined as 10 or more adenomas
within the liver. In contradistinction to solitary adenomas,
adenomatosis occurs with similar frequency in male and female
patients. Imaging characteristics of the individual adenomas are
similar to those of a solitary lesion.

12. Focal Nodular Hyperplasia
Focal nodular hyperplasia (FNH) is the second most common benign
tumor of the liver after hepatic hemangiomas.
FNH consists of aggregates of hepatocytes and is thought to be
secondary to a proliferative response of hepatocytes secondary to an
underlying vascular malformation.
Biliary structures proliferate without connection to the adjacent biliary tree.
Kupffer cells are present, often in greater amounts than in the surrounding
normal liver parenchyma.
FNH typically solitary lesion in young female patients.

13. At US, color Doppler imaging may show central vessels in what is
typically a solid mass with no distinguishing imaging characteristics.
On gray-scale US images, the appearance is nonspecific and may
range from isoechoic to hypoechoic. Overall, the findings at US may
be very subtle, even in cases of large lesions.

14. At CT, FNH is typically slightly hyperattenuating to surrounding
normal parenchyma on precontrast images, but it may be
isoattenuating.
There is typically brisk homogeneous enhancement, possibly with
visualization of large feeding arteries, followed by early washout into
large draining veins during the portal venous phase.

16. This brisk homogeneous enhancement pattern is also seen on
contrast-enhanced dynamic MR images. At MR imaging, FNH is
typically isointense to hypointense on T1-weighted images and
slightly hyperintense to isointense on T2-weighted images.There is
typically brisk enhancement of the mass but not the central scar
during the arterial phase, with delayed filling in of the central scar

17. Hepatocellular nodules in cirrhosis
Hepatocellular nodules in cirrhosis should be classied as
regenerative nodule, dysplastic nodule low grade, dysplastic nodule
high grade, dysplastic nodule with subfocus of HCC, or HCC based
on the progression to frank malignancy.

18. Ultrasound
Surface Nodularity: (88% sensitive, 82-95% specific ) , overall coarse and heterogeneous
echotexture,
Segmental hypertrophy/atrophy
Caudate width: right lobe width >0.65 (43-84% sensitive, 100% specific)
Reduction of the transverse diameter (<30 mm) of the medial segment of the left lobe
(segment IV)
Signs of portal hypertension
Doppler flow changes
Splenomegaly
Ascites
Fatty change (variable)
Sono-elastography may also be useful to assess the amount of liver fibrosis. Suggested values
for diagnosis
>7 kPa: advanced fibrosis
12.5-15 kPa: cirrhosis

19. Typically, both regenerative and dysplastic nodules display nonspecific imaging
features at both US and CT. These nodules may show brisk early enhancement
on arterial phase CT scans, especially when dysplasia is present. Regenerative
nodules are typically isointense to background liver parenchyma on T1- and T2-
weighted images. However, nodules with foci of dysplasia may demonstrate high
signal intensity on T2-weighted images. Similarly to CT, MR imaging may
demonstrate arterial enhancement in dysplastic nodules.

20. Nodular Regenerative Hyperplasia
Nodular regenerative hyperplasia (NRH) is characterized by diffuse
hyperplasic nodules composed of hepatocytes in the absence of
fibrosis . NRH is a distinct entity from regenerative nodules
associated with cirrhosis
NRH is also associated with portal hypertension. NRH is also often
associated with underlying systemic diseases including lympho and
myeloproliferative disorders as well as autoimmune diseases, drug
exposure, and Budd- Chiari syndrome.

21. Heterogeneous hepatic parenchyma, nodular transformation, the sequelae of portal
hypertension.
At CT, the nodules are hypoattenuating on precontrast images with possible mild
enhancement and peripheral rim enhancement.
The nodules in NRH may be hypo-, iso-, or hyperintense on T1- and T2-weighted images.
They may demonstrate a halo on T2-weighted images and a peripheral ring of enhancement
on T1-weighted images, as on CT images, similar to regenerative nodules or metastases.

22. Regenerative nodules
USG and CT - too small to detect.
When regenerative nodules contain iron, they are termed siderotic
nodules.
Siderotic nodules- hyperdense on CT and hypointense on both T1
and T2.

23. Benign Hepatic Tumors of Cholangiocellular
Origin
Hepatic Cyst
Biliary Hamartomas
Peribiliary Cyst
Biliary Cystadenoma
Caroli Disease
Biliary Papillomatosis

24. Hepatic Cyst
Single/multiple.
These cysts are thought to arise from precursor microhamar-
tomas, lined by cuboidal Biliary epithelium.
Clinical presentation
Asymptomatic
Compressive symptoms (massive).

25. Fine cystic lesion with partial or complete septa are often visualized.
• In case of complications – debris, thickened septa and complex
internal fluid.

26. CT
On CT, a hepatic cyst demonstrates
homogeneous hypoattenuation (water
attenuation) the cyst does not
enhance
MRI
Hypointense on T1.
Extremely hyperintense on T2.

27. Biliary Hamartomas
CT typically reveals multiple, widely scattered, small (<1.5 cm), low-
attenuation lesions, the majority of which do not demonstrate discernible
enhancement.
Usually hypointense on T1-weighted images
High signal intensity on T2- weighted images. Similar mural enhancement
patterns are detectable at MR imaging.
Bile duct hamartomas, also referred
to as von Meyenburg complexes,
represent a focal proliferation of bile
ducts embedded in fibrous stroma.

28. Peribiliary Cyst
Peribiliary cysts represent cystic dilatation of glands in the bile duct
walls and are associated with cirrhosis, with portal hypertension.
Typically, these cysts are more prominent within the hepatic hilum
and larger, central portal tracts.
At US, rounded or tubular anechoic structures are seen along the
portal tracts, findings that may be mistaken for dilated bile ducts.
Similarly, hypoattenuating cystic structures are seen at CT and
hyperintense cystic structures are seen on T2-weighted MR images.

29. Biliary Cystadenoma
Biliary cystadenoma is a rare benigncystic neoplasm lined by mucin-
secreting epithelium.
Premalignant form of biliary cystadenocarcinoma.
Cystadenomas may become quite large, with lesions up to 35 cm
having been reported.
Cystadenomas - more typically multilocular cystic lesions, Internal
septa and mural nodularity,

30. Caroli Disease
Caroli disease is secondary to the failure of or an abnormality of the
embryologic remodeling of bile ducts and is among the ductal plate
malformations.
The larger ducts are affected, resulting in saccular dilatation of the
intrahepatic bile ducts. Although it was originally classifed as a type V
choledochal cyst on the basis of the Todani classi cation, current
understanding suggests that Caroli disease and choledochal cyst are
distinct entities.
Caroli disease is associated with biliary stasis, bile duct sludge and
stones, and cholangitis. In addition, patients with Caroli disease are at risk
for developing subsequent malignancy including cholangiocarcinoma.

31. In most patients, the intrahepatic ductal dilatation is segmental and
more often saccular than fusiform. Commonly, alternating areas of
stricture and dilatation are seen. A well-known imaging feature at
contrast-enhanced CT or MR imaging is the so-called central dot
sign, which represents enhancing fibrovascular bundles along the
margin or within the dilated bile ducts.

32. Biliary Papillomatosis
Imaging typically reveals segments of biliary ductal dilatation, which are
secondary to the multiple intraluminal filling defects associated with
the papillomas or to the presence of significant intraluminal mucin.
US demonstrates nonshadowing flling defects and biliary dilatation as well as
the presence of the sludgelike intraluminal mucin. MR imaging has been
shown to have high sensitivity for detection of biliary papillomas
Rare
Numerous papillary adenomas involving
the intra and extrahepatic bile ducts.
premalignant condition with significant risk
of malignant transformation.

34. Benign Hepatic Tumors of
Mesenchymal Origin
Cavernous Hemangioma
Focal Fat
Angiomyolipoma
Lipoma
Peliosis Hepatis
Paraganglioma
Infammatory Pseudotumor

35. Cavernous Hemangioma
Cavernous hemangiomas represent the most common primary liver
tumor and consist of multiple large, blood filled vascular channels.,
Solitary, although multiplicity is not uncommon.
Typically small, giant cavernous hemangiomas may range in size to
greater than 20 cm.
Associated with several clinical syndromes including Klippel-
Trenaunay-Weber syndrome, Osler-Rendu-Weber disease, and von
Hippel–Lindau disease, all of which are associated with hepatic
hemangiomas .

36. Hemangiomas have characteristic imaging appearances in US,
hemangiomas appear as focal, homogeneous and hypovascular,
echogenic lesions;
This appearance is variable
depending on the degree of
fatty infiltration or fibrosis of the
liver, which may result in a
relatively hypoechoic appearance
of the lesion.
US contrast agents may be useful in characterizing hepatic
hemangiomas in cases with atypical appearances related to fatty
infiltration of the liver .

37. Hemangiomas are typically hypoattenuating to liver parenchyma at
unenhanced CT - the well-known peripheral nodular enhancement
with centripetal progression, resulting in diffuse high attenuation on
delayed phase images.
Flash filling - small hemangioma or enhancement arterial phase
Larger lesions may not demonstrate - uniform enhancement on
delayed phase images, possibly owing to areas of thrombosis.
Central scars may be seen in hepatic hemangiomas.

38. At MR imaging, hepatic hemangiomas typically demonstrate
Low signal intensity on T1- weighted images
Marked high signal intensity onT2-weighted images.
Postcontrast MR imaging characteristics are similar to those of CT.

39. Focal Fat
The different manifestations of fatty replacement in the liver include
focal, patchy, and diffuse infiltration. Focal fatty infiltration and focal
fatty sparing may pose a diagnostic dilemma at imaging, manifesting
as a “pseudolesion.”

40. In US, focal fatty infilltration may be seen as a focal, well-
circumscribed, echogenic area.
CT demonstrates focal areas of relative low attenuation.
MR imaging provides a useful method for characterizing suspected
geographic fatty infiltration by using in-phase and opposed- phase
gradient-echo T1-weighted sequences. The relative increase in
intravoxel fat in areas of focal fatty infiltration demonstrates decreased
signal intensity on the opposed-phase images relative to that on the in-

41. In contradistinction, focal fatty sparing typically appears hypoechoic
relative to surrounding fatty infiltration.
At CT, areas of fatty sparing appear hyperattenuating relative to
surrounding steatosis.
Finally, at MR imaging, areas of fatty sparing may be identified owing
to lack of a decrease in signal intensity on opposed-phase gradient-
echo T1-weighted images and appear hyperintense relative to
surrounding steatosis.

42. Angiomyolipoma
Hepatic angiomyolipomas are a rare benign tumor of
the liver composed of smooth muscle, blood vessels,
and a variable amount of adipose tissue.
• Composed of mature fat, blood vessels and smooth
muscle cells.
• It is not capsulated.
• Tuberous sclerosis is a known association of hepatic
angiomyolipoma.

43. US - Circumscribed hyperechoic lesions
may show some attenuation and subtle
shadowing as well as relative
hypervascularity at US.
CT - Areas of macroscopic fat - On
contrast-enhanced CT images, hepatic
angiomyolipomas typically demonstrate
marked enhancement during the arterial
phase, often with visualization of large
central vessels.

44. MR imaging- Macroscopic fat may be detected by using fat
suppression techniques

45. Peliosis Hepatis
Rare,
Sinusoidal dilatation and blood filled hepatic spaces.
At US, peliosis hepatis demonstrates variable echogenicity relative to
the surrounding liver and may have internal vascularity on color
Doppler images. In patients with normal livers, peliosis is typically
hyperechoic; however, it may appear hypoechoic in patients with
abnormally echogenic liver parenchyma, such as in steatosis.

46. On CT, peliosis is commonly seen as a focal hypoattenuating area;
however, areas of hemorrhage may increase the attenuation . At
contrast-enhanced CT, early globular enhancement is typically
identified with a centripetal increase in enhancement during later
phases of imaging. Central areas of thrombosis or areas of internal
calcification may also be seen.

47. At MR imaging, peliotic lesions are typically hypointense on T1
weighted images owing to subacute blood products, but the signal
intensity may be variable. On T2-weighted images, the lesions are
commonly hyperintense with smaller foci of increased signal intensity
centrally, which are possibly related to necrosis. Enhancement
characteristics at MR imaging are similar to those at CT.

48. Inflammatory Pseudotumor
Inflammatory pseudotumor is a benign hepatic tumor consisting of
inflammatory cells and fibrous stroma. The cause of these lesions is
unknown, although they have been speculated to be secondary to an
inciting hepatic infection
At US, inflammatory pseudotumors have been described as hypo- as
well as hyperechoic masses with increased through transmission and
visualization of multiple septa.

49. On CT - Nonspecfic imaging findings.
Hypoattenuating to liver parenchyma on unenhanced images, and
variable patterns of enhancement are seen after contrast material
administration, including peripheral enhancement or enhancement of
multiple internal septa .
On MR lesions are typically hypointense on T1-weighted images and
hyperintense on T2-weighted images with variable enhancement
patterns.