LAUSR

Local T-stage in bladder cancer depends on the depth of tumor invasion through the lamina propria (T1) and muscle layers (T2) of the bladder wall, the presence of penetration into the perivesical fat (T3), or tumor spreading to an adjacent organ or abdominal or pelvic wall (T4). Preoperative imaging studies can play an important diagnostic role in distinguishing superficial from muscle-invasive bladder tumors, with considerably different treatment options between the two [1–4]. The ‘‘inchworm sign’’ is a characteristic finding on diffusion-weighted magnetic resonance imaging (DWMRI) proposed as a criterion for T-staging in nonmuscle-invasive bladder cancer [1, 2]. Several studies have reported about the added value of DW-MRI in preoperative T-staging in patients with bladder cancer, especially when combined to high-resolution T2-weighted sequences [1, 3–5]. On DW-MRI, local staging is performed according to the difference in the signal intensity (SI) between bladder cancer and the surrounding tissue. Bladder cancer shows high SI while the submucosal and muscle layers show low and intermediate SI, respectively [1, 5]. The ‘‘inchworm sign’’ is usually indicative of nonmuscle-invasive bladder cancer on the basis of an uninterrupted low submucosal signal (meaning stage T1 or lower). It consists of a high SI band corresponding to the tumor over a low SI submucosal stalk or thickened submucosa, showing an arch-shaped appearance which