Table 4.

Organ Procurement and Transplantation Networks classification system for nodules seen on images of cirrhotic livers

OPTN class 0
Incomplete or technically inadequate study	Repeat study required for adequate assessment; automatic priority MELD points cannot be assigned on basis of an imaging study categorized as OPTN class 0
OPTN class 5
Meets radiologic criteria for HCC	May qualify for automatic exception, depending on stage
Class 5A: ≥ 1 cm and < 2 cm measured on late arterial or portal venous phase images	Increased contrast enhancement in late hepatic arterial phase AND washout during later phases of contrast enhancement AND peripheral rim enhancement (capsule or pseudocapsule)
Class 5A-g: Same size as OPTN class 5A HCC	Increased contrast enhancement in late hepatic arterial phase AND growth by 50% or more documented on serial CT or MR images obtained ≤ 6 mo apart
Class 5B: Maximum diameter ≥ 2 cm and ≤ 5 cm	Increased contrast enhancement in late hepatic arterial phase AND either washout during later contrast phases OR peripheral rim enhancement (capsule or pseudocapsule) OR growth by 50% or more documented on serial CT or MR images obtained ≤ 6 mo apart (OPTN class 5B-g)
Class 5T: Prior regional treatment for HCC	Describes any residual lesion or perfusion defect at site of prior UNOS class 5 lesion
Class 5X: Maximum diameter ≥ 5 cm	Increased contrast enhancement in late hepatic arterial phase AND either washout during later contrast phases OR peripheral rim enhancement (capsule or pseudocapsule)

Adpated from Wald et al[30]. HCC: Hepatocellular carcinoma; OPTN: Organ Procurement and Transplantation Networks; MELD: Model for End stage Liver Disease; CT: Computed tomography; MR: Magnetic resonance; UNOS: United Network for Organ Sharing.