Management of indeterminate hepatic nodules and evaluation of factors predicting their malignant potential in patients with colorectal cancer.

Some liver nodules remain indeterminate despite hepatocyte-specific contrast MRI in patients with colorectal liver metastasis (CRLM). Our objective was to study the natural course and evaluate possible treatment strategies for indeterminate nodules. We retrospectively evaluated patients in whom MRI revealed 'indeterminate' or 'equivocal' nodules between January 2008 and October 2018. Patients were followed up until October 2019 or until death (median, 18 months; (1-130 months)). The incidence of patients with indeterminate nodules on MRI was 15.4% (60 of 389). The sensitivity and specificity of intraoperative ultrasound for detecting indeterminate nodules were 73.68% and 93.75%, respectively, with a positive predictive value of 96.6%. Over half of the patients followed up had benign nodules (58.8%). By comparing characteristics of patients with benign or malignant nodules in the follow up group, the ratio of positive lymph nodes to total number of lymph nodes resected (pLNR) was significantly greater in patients with malignant nodules (P = 0.006). Intraoperative ultrasound could be considered as an adjunct to MRI in patients with indeterminate nodules owing to its high positive predictive value. The pLNR could be used to help select which patients can undergo conservative therapy, at least in metachronous CRLM.