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

PURPOSE: To retros p p y 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 materia I- 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. RSNA, 2005.