Hepatocellular adenoma

Case contributed by Dr Jan Frank Gerstenmaier

Presentation

Right flank abscess. Incidental liver lesions on CT, for investigation.

Patient Data

Age: 32
Gender: Female
MRI

Multiplanar multisequence imaging of the liver, including MRCP and dynamic post-contrast sequences (Primovist). Comparison is made to external MRI dated XXXX 2014.

Study degraded by respiratory motion artefact.

A 5.4 x 4.0 cm lesion in hepatic segment 7/6 and is slightly hyperintense to liver on T2 and isointense on T1. Signal intensity or does not decrease on out of phase T1 imaging (unlike the rest of the background liver, due to mild steatosis). The lesion shows arterial enhancement with washout through the portal venous and delayed phases and a thin pseudocapsule. No contrast uptake in the hepatocellular phase.

A 1 cm T2 hyperintense lesion is seen at the periphery of segment 5. This shows arterial enhancement that becomes isointense to liver of subsequent phases, including the hepatocellular phase.

An 8 mm T2 hyperintense lesion in segment 7 shows apparent progressive peripheral enhancement, and no uptake on on hepatocellular phase.

The common hepatic and common bile ducts measure up to 7 mm in diameter, which may reflect the patient is post cholecystectomy status. No choledocholithiasis is identified. The pancreas has a normal appearance.

A 1.8 x 0.9 cm lesion is seen in the posterior to segment 6 within Morrison's pouch. This lesion is hyperintense on T2, with possible peripheral enhancement. A small residual collection is likely. Further likely collections around the anterior and lateral liver surface, and around the head of the pancreas.

In the right abdominal wall musculature, between obturator internus and transverse abdominus there is a complex 9 x 4 cm T2 hyperintense region, likely a collection. This is only well seen on the coronal images, but the superior component is seen on the axial post contrast images and there appears to be peripheral enhancement. This is similar to when was seen on CT dated XXXXX 2014.

Conclusion:

Large lesion in segments 7/6 is favoured to represent a lipid poor hepatic adenoma, on a background of hepatic steatosis. The small segment 5 lesion is likely a focal nodular hyperplasia (FNH).

Persistent collections in Morrison's pouch, around the pancreas head and in the right abdominal wall.

CT

CT Abdomen and Pelvis:

Oral and intravenous contrast enhanced images have been obtained. Comparison made to external study dated XXXX 2014.

Findings:

Within the right transversus abdominis muscle laterally there is a lobulated 7.5 x 3.4 x 7.1 cm hypodense collection with a thick peripheral enhancing rim. There is an adjacent 1.6 x 2.6 x 8.4 cm collection component medially which does not appear to communicate with the larger lateral collection. There is stranding of the adjacent oblique muscles and the peritoneal fat. A trace amount of fluid is seen within Morison's pouch which appears to have a peripheral enhancing rim.

A large 18.4 x 8.6 x 10.0 cm fluid collection is identified within the posterolateral abdominal subcutaneous tissues. This has a linear tract extending to the abdominal wall collection just superior to the iliac crest.

3.7 x 4.9 cm peripheral enhancing lesion within segment 6 of the liver is again demonstrated.

Four subcentimetre cysts identified within the interpolar region of the right kidney. The spleen, adrenals and pancreas are unremarkable. Previous cholecystectomy noted.

No inguinal or intra-abdominal lymphadenopathy.

The imaged lung bases are clear.

No suspicious osseous lesion identified.

Conclusion:

Lobulated collections involving the right transversus abdominis muscle laterally with possible linear tract communication to a larger posterolateral subcutaneous collection inferiorly.

Rim enhancing structure indenting or arising from posteroinferior tip of liver may be a chronic collection related to Morison's pouch rather than a liver parenchymal lesion.

Segment 6 liver lesion is similar in appearance to external CT. External abdominal MRI noted.

 

Ultrasound

Segment VI liver mass is hypoechoic relative to liver parenchyma

Pathology

Morbid obesity, increasing liver lesion seg 6/7 liver adenoma? Swab from intraductal pus/GB bed.

MACROSCOPIC DESCRIPTION: 1. "Seg 6/7 (liver) adenoma": A partial hepatectomy 130x90x42mm and 311gms. There is a resection margin 145x90mm (inked black). The liver capsule is shiny, smooth and intact (inked blue). Underlying the liver capsule is a well demarcated rubbery tan tumour 75x53x35mm. The tumour is 9mm from the resection margin. On the liver surface, 37mm from the resection margin, there is a well demarcated cystic cream lesion containing purulent material 22x20x11mm. The purulent lesion contains a calculus up to 4mm. The remaining liver parenchyma is unremarkable. A swab of the purulent material sent to microbiology. A sample of tumour and normal tissue sent to tissue bank. BLOCK DESIGNATION: A-B - Tumour with resection margin C-D - Tumour with liver capsule E-F - Tumour with adjacent normal liver G-H - Cystic purulent lesion I - Normal liver parenchyma. P9. 2. "Seg 6 (Liver)": A partial hepatectomy 105x90x64mm, 203gms. There is a resection margin 105x74mm (inked black). The liver capsule is intact, shiny and smooth with a small area of roughening up to 24mm (inked blue). No focal lesion is identified within the parenchyma. BLOCK DESIGNATION: A-B - Resection margin C - Roughened liver capsule D - Unremarkable liver capsule P4.

MICROSCOPIC DESCRIPTION: 1. Sections of the liver show a well-demarcated hepatocellular tumour. It forms trabeculae with no more than 2-cell in thickness. The hepatocytes show no nuclear atypia or dysplasia. Within the lesion, the portal tracts are poorly formed with absence of interlobular bile ducts. No rupture of the liver capsule is seen. Sinusoidal dilatation is present and thick-walled blood vessels are inconspicuous. There are aggregates of lymphocytes in the portal tracts and in some sinusoids. The remaining liver parenchyma shows moderate predominantly macrovesicular steatosis, involving about one third of the parenchyma. Steatohepatitis is seen, in which clusters of neutrophils surround hepatocytes. There is one area where a calculus is present. It is surrounded by suppurative granulomatous inflammation. The Gram stain shows no bacteria. The Grocott stain shows no fungi. The Ziehl-Neelsen stain shows no acid fast bacilli. The Perl's stain shows no iron deposits in the hepatocytes. The Orcein stain shows no copper binding protein. The Masson trichrome stain shows mild portal fibrosis. There is no bridging fibrosis or cirrhosis. The features are those of hepatocellular adenoma. It is completely excised. The tumour cells are amyloid-A and B-catenin negative. Further immunostains for subtyping will be performed at XXXXX Hospital. 2. Sections of the liver show no tumour. The parenchymal changes with steatosis are seen as described above. DIAGNOSIS: 1. Seg 6/7 liver: Hepatocellular adenoma, completely excised. 75mm in size. No evidence of malignancy. 2. Seg 6 liver: No tumour identified.

Case Discussion

Hepatocellular adenoma was confirmed at histology following resection. Beta-catenin was negative - this subtype of HCA has an increased risk of dedifferentiation into hepatocellular carcinoma. Note there was no intralesional fat on imaging, however the liver was fatty and steatohepatitis was confirmed at histology.

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Case information

rID: 31000
Case created: 15th Sep 2014
Last edited: 7th Jan 2016
Inclusion in quiz mode: Included

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