Hepatic lesions deemed too small to characterize at CT: prevalence and importance in women with breast cancer.

PURPOSE To retrospectively evaluate the prevalence and clinical importance of hepatic lesions considered too small to characterize (TSTC) at initial computed tomography (CT) in women with breast cancer. MATERIALS AND METHODS Approval for this retrospective study was obtained from the institutional review board, which waived the requirement for informed consent. For each woman who received a diagnosis of breast cancer between 1998 and 2002, the authors reviewed the report of the first contrast material-enhanced CT examination that included assessment of the liver. For women with no definite liver metastasis and at least one hepatic lesion considered TSTC, reports of follow-up imaging examinations were reviewed for a change in lesion size; medical records and images were reviewed if there was a change in lesion size. The 95% confidence intervals (CIs) were calculated for best- and worst-case analyses of cases in which different assumptions were used to classify a lesion as benign. RESULTS Of 7692 women, 1012 (13.2%) underwent contrast-enhanced CT including liver assessment. The mean age of the 1012 women was 54.6 years (range, 20.7-89.1 years). The median time from diagnosis of breast cancer to initial CT examination was 14.1 weeks (range, -3.7 to 296 weeks). The presence of at least one hepatic lesion deemed TSTC was reported in 277 of 941 women (29.4%) in whom no definite hepatic metastasis was reported. Subsequent imaging examinations were performed in 191 of the 277 women (69.0%) (median time from initial CT to last follow-up imaging examination, 54 weeks; range, 0.3-302 weeks). Those examinations revealed the lesions were unchanged in 175 (91.6%) women, no longer visible in eight (4.2%), and larger in six (3.1%). In two women (1.0%), change could not be determined. The enlarging hepatic lesions deemed TSTC represented metastatic breast cancer (three patients), metastatic pancreatic cancer (one patient), or cysts (one patient); in one patient, the etiology was not known. Results of best- and worst-case analyses showed that the lesions were benign in 96.9% (95% CI: 93%, 99%) and 92.7% (95% CI: 88%, 96%) of women, respectively. CONCLUSION In 92.7%-96.9% of women with breast cancer and hepatic lesions deemed TSTC but no definite liver metastases at initial CT, the lesions represented a benign finding.