Diffusion-weighted magnetic resonance imaging of thymoma: ability of the Apparent Diffusion Coefficient in predicting the World Health Organization (WHO) classification and the Masaoka-Koga staging system and its prognostic significance on disease-free survival

Objectives To evaluate the usefulness of diffusion-weighted magnetic resonance for distinguishing thymomas according to WHO and Masaoka-Koga classifications and in predicting disease-free survival (DFS) by using the apparent diffusion coefficient (ADC). Methods Forty-one patients were grouped based on WHO (low-risk vs. high-risk) and Masaoka-Koga (early vs. advanced) classifications. For prognosis, seven patients with recurrence at follow-up were grouped separately from healthy subjects. Differences on ADC levels between groups were tested using Student- t testing. Logistic regression models and areas under the ROC curve (AUROC) were estimated. Results Mean ADC values were different between groups of WHO (low-risk = 1.58 ± 0.20 × 10 -3 mm 2 /sec; high-risk = 1.21 ± 0.23 × 10 -3 mm 2 /sec; p