Suspicious Axillary Lymph Nodes Identified on Clinical Breast MRI in Patients Newly Diagnosed with Breast Cancer: Can Quantitative Features Improve Discrimination of Malignant from Benign?

Rationale and Objectives: To determine whether quantitative dynamic contrast-enhanced (DOE) and diffusion-weighted (DW) magnetic resonance imaging (MRI) features can discriminate malignant from benign axillary lymph nodes (ALNs) identified as suspicious on clinical breast MRI in patients newly diagnosed with breast cancer. Materials and Methods: After approval from institutional review board, all clinical breast MR examinations performed from March 2006 through January 2010 describing at least one morphologically suspicious ipsilateral ALN in patients with newly diagnosed breast cancer were identified. Each suspicious ALN underwent ultrasound-guided core needle biopsy, and nodes with benign results were subsequently sampled surgically. Quantitative DOE and DW MRI parameters (diameters, volume, enhancement kinetics, and apparent diffusion coefficients [ADC]) were measured for each suspicious ALN and a representative contralateral normal node, and each feature was compared between the ALN groups (normal, benign, and malignant). Results: Thirty-four suspicious ALNs (18 malignant and 16 benign) and 34 contralateral normal-appearing ALNs were included. Suspicious malignant and benign nodes exhibited larger size, greater volume, and lower ADCs than normal ALNs (P < .05). Among suspicious ALNs, the only quantitative measure that discriminated between malignant from benign outcome was percent of ALN demonstrating washout kinetics (P = .02). Conclusions: In ALNs deemed morphologically suspicious on breast MRI, quantitative MRI features show little value in identifying those with malignant etiology.