2005 PRETEXT: a revised staging system for primary malignant liver tumours of childhood developed by the SIOPEL group

Abstract

Over the last 15 years, various oncology groups throughout the world have used the PRETEXT system for staging malignant primary liver tumours of childhood. This paper, written by members of the radiology and surgery committees of the International Childhood Liver Tumor Strategy Group (SIOPEL), presents various clarifications and revisions to the original PRETEXT system.

Fig. 1

Schematic representations of the segmental anatomy of the liver. a Frontal view of the liver. The numerals label Couinaud’s segments 2 to 8. b The hepatic veins (black) and the intrahepatic branches of the portal veins (grey) are shown. Segment 1 (equivalent to the caudate lobe) is seen to lie between the portal vein and the inferior vena cava. c Exploded frontal view of the segmental anatomy of the liver. The umbilical portion of the left portal vein (LPV) separates the left medial section from the left lateral section (LLS). Segment 1 is obscured in this view. Note that the term “section” has been used in preference to “segment” or “sector” (see text). d Transverse section of the liver shows the planes of the major venous structures used to determine the PRETEXT number. The hepatic (blue) and portal (purple) veins define the sections of the liver (2–8). This schematic diagram shows how the right hepatic (RHV) and middle hepatic (MHV) veins indicate the borders of the right anterior section (RAS) with the right posterior (RPS) and left medial (LMS) sections. Note that the left portal vein (LPV) actually lies caudal to the confluence of the hepatic veins and is not seen in the same transverse image. The left hepatic vein (LHV) runs between segments 2 and 3 and is not used in PRETEXT staging

Fig. 2

PRETEXT I. a The left lateral section (segments 2 and 3) is involved. b The right posterior section (segments 6 and 7) is involved

Fig. 3

PRETEXT II. a Tumour involving only the right lobe of the liver. b A transverse T1-weighted MR image of a child with hepatoblastoma shows that the middle hepatic vein (arrow) is displaced but not involved by the tumour. This is the most common type of PRETEXT II tumour. c Tumour involving only the left lobe of the liver. d Tumour involving only the left medial section. e Tumour involving only the right anterior section. f Multifocal tumours involving only the left lateral and right posterior sections. g The tumour is confined to the caudate lobe (PRETEXT II C1, see text; RPV right portal vein)

Fig. 4

PRETEXT III. a Extensive tumour sparing only the left lateral section. b Extensive tumour sparing only the right posterior section. c Anterior central liver tumour involving the left medial and right anterior sections. d Contrast-enhanced CT image shows a central liver tumour lying between the left portal vein (white arrow) and the right hepatic vein (black arrow). e Multifocal PRETEXT III tumour, sparing the right anterior section. f Multifocal tumours sparing only the left lateral and right anterior sections. g Multifocal tumours sparing only the left medial and right posterior sections

Fig. 5

PRETEXT IV. a Multifocal PRETEXT IV tumours involve all four sections. b Contrast-enhanced CT image of a patient with PRETEXT IV F1 (see text) hepatoblastoma. c Unifocal PRETEXT IV tumours often have a diffuse growth pattern. d Contrast-enhanced CT image of a patient with diffuse PRETEXT IV hepatoblastoma

Fig. 6

Extrahepatic abdominal tumour extension. This composite of contrast-enhanced CT images in a patient with hepatoblastoma shows growth of the primary tumour through the diaphragm into the thorax (E1). The 2005 PRETEXT system no longer requires biopsy proof for this form of tumour spread

Fig. 7

Involvement of the portal and hepatic venous systems. a When the tumour (grey) approaches or abuts the vein (black), there is no venous involvement, even if the vein is partly encased. b Complete obstruction or encasement of the vein is one form of involvement. Obstruction of the inferior vena cava by extrinsic compression, however, does not count as involvement (see text). c Intravascular tumour growth in the portal and/or hepatic venous systems is not uncommon in children with hepatoblastoma or hepatocellular carcinoma. d Transverse ultrasound image of the right lobe of the liver in a patient with hepatoblastoma. The tumour (white circles) has grown into the right branch of the portal vein (P1a), disrupting the normal “white line” of the vein wall (arrows)