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case_images: The results of preoperative examination. (A) CTU indicated a space occupying lesion (6.0 cmx5.0 cm) in the left posterior wall of the bladder with heterogeneous enhancement in the excretory phase. (B-D) MRI indicated bladder tumor (6.0 cmx5.1cmx3.5cm) with mixed high SI on T2WI in transverse plane (B) and slightly equal SI on T1WI in sagittal position (C) and coronal position (D).
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case_images: The computed tomography urography (CTU) scan indicated a space occupying lesion (6.0 cmx5.0 cm) in the left posterior wall of the bladder with heterogeneous enhancement in the excretory phase ( Figure 1A ). T1-weighted imaging (T1WI) and mixed high SI on T2-weighted imaging (T2WI) (6.0 cmx5.1cmx3.5cm) in the left posterior wall of the bladder ( Figures 1B-D ). The preoperative diagnosis was huge bladder tumor. Postoperative pathological examination revealed bladder IMT ( Figure 2F ), with immunohistochemistry (IHC) positive for Ki-67 (15-20%), cytokeratin AE1/AE3 (CK AE1/AE3), smooth muscle actin (SMA), and Desmin of bladder IMT and negative for anaplastic lymphoma kinase (ALK) of bladder IMT as well as fluorescence in situ hybridization (FISH) negative for ALK gene rearrangement ( Figures 2G-I ,  Supplementary Figures 1A-C ).
case_images: The En bloc resection of bladder tumor (EBRBT) and pathologic results. (A) Intraoperative cystocopic view of the huge bladder IMT. (B) At the base of the tumor, the circumferential margin was incised initially with 1470 nm diode laser to access the detrusor muscle layer. (C) The whole tumor was en bloc resected. (D, E) The enucleated en bloc tumor was removed by the morcellator system. (F) The result of first postoperative pathology with HE staining in bladder IMT. (G-I) The results in IHC staining of ALK(-) (G), Ki-67+(15-20%) (H) and FISH of ALK gene rearrangement(-) (I).
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case_images: F continuous-flow cystoscopy (Batch no.DQH-111, Hawk, Hangzhou, China). Firstly, we performed a thorough cystoscopic examination of the bladder and located an about 6.0x5.0cm polypoid tumor in the left posterior wall of bladder ( Figure 2A ). The circumferential margin was incised down to the detrusor muscle layer, causing the entire tumor to retract towards the center upon releasing the mucosa and submucosa. ( Figure 2B ). The muscle fiber was separated by laser from the tumor's base at the visible anatomical level until the whole tumor was en bloc resected ( Figure 2C ). The enucleated tumor was removed by the morcellator system ( Figures 2D, E ). Postoperative pathological examination revealed bladder IMT ( Figure 2F ), with immunohistochemistry (IHC) positive for Ki-67 (15-20%), cytokeratin AE1/AE3 (CK AE1/AE3), smooth muscle actin (SMA), and Desmin of bladder IMT and negative for anaplastic lymphoma kinase (ALK) of bladder IMT as well as fluorescence in situ hybridization (FISH) negative for ALK gene rearrangement ( Figures 2G-I ,  Supplementary Figures 1A-C ).
case_images: The second TUR and postoperative pathology results. (A) Intraoperative cystoscopic view of the surgical scar and inflammatory edema areas before second TUR. (B, C) The surgical scar and inflammatory edema areas were completely enucleated in second TUR with 1470 nm diode laser (B), and surgical site after second TUR with 1470 nm diode laser (C). (D) The result of second postoperative pathology with HE staining indicated chronic inflammation.
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case_images: IMT. Intraoperative cystoscopic examination showed that the surgical scar and inflammatory edema area were visible on the left posterior wall of the bladder ( Figure 3A ). The muscle fiber was cut until the entire scar and inflammatory edema area were enucleated ( Figures 3B, C ). The second postoperative pathology report showed chronic inflammation concomitant with edema of the bladder mucosa without bladder IMT, furthermore no tumor was observed in muscularis propria layer of bladder ( Figure 3D ).
case_images: The results of follow-up examination after operation. (A-C) MRI showed no tumor recurrence on T2WI in coronal position (A) and transverse plane (C) and no tumor recurrence on T1WI in sagittal position (B) on postoperative month 14. (D) Flexible cystoscopy showed the performance of surgical wound healing on postoperative month 24. (E) The flowchart of timeline for diagnosis and treatment process.
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case_images: On postoperative month 14, the result of MRI showed no recurrence or distal metastasis of bladder IMT ( Figures 4A-D ). The flowchart of the timeline for the diagnosis and treatment schedule is shown in  Figure 4E .