Organ-confined urinary bladder carcinoma: a comparative analysis for 'submucosal linear enhancement' sign on early phase of DCE-MRI and the 'inchworm' sign on DWI

Objective: To analyze the 'submucosal linear enhancement' sign on early phase of DCE-MRI and the 'inchworm' sign on DWI for the pathogenetic mechanism and value in preoperative staging of organ confined bladder carcinoma. Methods: 59 patients with suspected or confirmed urothelial bladder cancer and no renal function impairment were enrolled in the study. All patients underwent MRI within 2-weeks before surgery. Two image sets of T₂WI&DW-MRI and T₂WI&DCE-MRI were independently interpreted by two readers at 2-week intervals by analyzing whether there were 'inchworm' sign on DWI and 'submucosal linear enhancement' sign on early phase of DCE-MRI in comparison with pathology. Tumor size was also compared. Results: 92 carcinomas with (42) and without (50) inchworm sign on DWI were analyzed. 42 carcinomas with 'submucosal linear enhancement' on early phase of DCE-MRI manifested as continuous linear enhanced submucosa gathering toward into the center of tumor (38, 35 stage T₁ and 3 stage T₂), continuous straight and no gathering linear enhanced submucosa (3, all stage T₁), or interrupted linear enhanced submucosa (1, stage T₂). The remaining 50 lesions without inchworm sign included 34 (30 stage T₁, 4 stage T₂) without linear enhanced submucosa, 11 (10 stage T₁, 1 stage T₂) with continuous straight and no gathering linear enhanced submucosa, 4 (1 stage T₁, 3 stage T₂) with interrupted linear enhanced submucosa, and 1 (stage T₂) with continuous linear enhanced submucosa gathering toward into the center of tumor. Conclusion: Presentation and manifestation of 'submucosal linear enhancement' under the tumor base on DCE-MRI is a significant imaging sign, which can be helpful in the differentiation of tumors in stage T₁ or lower versus those in stage T₂ bladder urothelial carcinoma. Tumors smaller than 10 mm without submucosal linear enhancement are often stage T₂. Tumors larger than 10 mm showing continuous submucosal linear enhancement either straight or gathering toward into the tumor center are stage T₁. (authors)