Outcome of liver lesions indeterminate for malignancy on ultrasound: the role of patient age, risk status, and lesion echogenicity

The purpose of this study was to evaluate the relationship between final outcome of lesions indeterminate for malignancy on ultrasound (US) and patient and imaging characteristics. We identified all patients with indeterminate liver lesions on US between 9/1/2013 and 12/31/2014 using institutional codes based on radiologist opinion. Miscoded lesions (n = 30) and patients with no imaging, pathology, or clinical follow-up at our health system (n = 6) were excluded. Final diagnostic category of malignant, benign, pseudolesion, or indeterminate was assigned using imaging, pathology, and clinical follow-up. Differences in diagnostic categories were compared by patient (age, gender, race, known malignancy. or liver disease) and imaging characteristics (lesion size, echogenicity. and number). Independent likelihood of a benign final diagnostic category was adjusted for significant variables on univariate analysis. Indeterminate liver lesions on US were found in 153/6813 patients (2%). Final diagnostic categories were malignant (11/153, 7%), benign (94/153, 61%), pseudolesion (42/153, 27%). and indeterminate (6/153, 4%). Nearly one-third of hypoechoic masses in patients with known malignancy or liver disease (i.e., high-risk status) ≥ 46 years of age were malignant (9/28, 32%). On multivariate analysis, patients of age ≥ 61 years and high-risk status were associated with decreased likelihood of benign diagnostic category (OR .19 (95% CI .07–.51) and OR .40 (95% CI .18–.88), p values .001 and .022, respectively). 2% of patients undergoing abdominal US have sonographically indeterminate liver lesions, of which 7% are malignant. Older, high-risk patients with hypoechoic lesions should receive short-term follow-up as one-third will have malignant lesions. Younger, low-risk patients should receive conservative follow-up, regardless of US imaging features.