Purpose: 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.
Methods: 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.
Results: 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).
Conclusions: 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.
Keywords: Focal liver lesions; Indeterminate liver lesion; Liver neoplasm; Liver ultrasound.