Overestimating the size of hepatic malignancy on helical CT during arterial portography: equilibrium phase CT and pathology.

PURPOSE: Overestimating the size of hepatic malignancy with helical CT during arterial portography (CTAP) can be a potential pitfall in determining liver resection area. We evaluated the prevalence and extent of overestimation of hepatic malignancy on CTAP in correlation with helical equilibrium phase CT (EPCT) and pathologic findings.

METHOD: CTAP and EPCT in 47 histologically proven malignant hepatic tumors [33 hepatocellular carcinomas (HCCs) and 14 metastases] in 39 patients were retrospectively studied. Nineteen tumors were resected and pathologically evaluated.

RESULTS: The size overestimation ratios (CTAP/EPCT) ranged from 1.02 to 1.56 (mean +/- SD 1.24 +/- 0.16) in HCC and from 1.00 to 2.48 (1.34 +/- 0.42) in metastasis. In 19 surgical specimens, the overestimation ratios (CTAP/specimen) ranged from 1.05 to 1.45 (1.20 +/- 0.13) in HCC and from 1.10 to 1.38 (1.22 +/- 0.10) in metastasis. Histopathologically, flattening of parenchymal structures (100%), atrophy of hepatic cords (95%), sinusoidal congestions (95%), fibrosis and ductular proliferation (58%), and no tumor were seen in peritumoral parenchyma corresponding to perilesional perfusion defects with CTAP.

CONCLUSION: CTAP frequently and significantly overestimates the size of malignant hepatic tumors. This phenomenon is attributable to either benign histopathological changes in the perilesional liver parenchyma caused by parenchymal compression or portal venous obstruction by malignant liver tumors or to a siphoning effect by hypervascular neoplasms.