Uroradiology & genital male imagingCase Type
Fernando González Tello, Isabel García Gómez Muriel, María Cristina González Gordaliza, Rafael Rodríguez-Patrón Rodríguez, María Muñoz Beltrán, Javier Blázquez SánchezPatient
70 years, male
We assessed a 70-year-old patient in urology follow-up for benign prostatic hyperplasia (BPH). He was asymptomatic and under treatment with tamsulosin. His prostate-specific antigen (PSA) levels were slightly elevated since 2016, last control in October 2020 with a value of 6.73 ng/ml. There were no significant alterations in the digital rectal exam.
Given the patient's symptoms, an MRI was requested (1.5 Tesla MRI available in our hospital) that showed an enlarged prostate with a volume of approximately 72cc and several nodular lesions of varying signal intensity in relation to BPH (fig. 2A, 3A).
Incidentally, a polypoid lesion dependent on the trigone/bladder neck was observed, with an inverted "C" morphology (fig. 1A, 2A, 3A). It presented a focal increase of signal in diffusion at b value = 1500 s / mm2, "inchworm sign" (fig. 1B, 1C, 2B, 2C, 3B) and an intense focal and early enhancement in the dynamic study (fig. 1D). The findings were highly suspicious of primary urothelial carcinoma.
Pathological confirmation was carried out by transurethral resection, which revealed fragments of urothelial carcinoma with a low-grade inverted pattern that did not infiltrate the lamina propria or the muscular layer. PTa G1 stage (AJCC 8th edition) 
Urinary bladder cancer (UBC) is one of the most common urological malignancies. In the Western world, bladder cancer is the fourth most common malignancy in men and the eighth-most common in women .
The local T stage in bladder cancer depends on the depth of tumour invasion through the lamina propria (T1), the muscular layer propria of the bladder wall (T2), the presence of penetration into perivesical tissues (T3) or the spread of the tumour to an adjacent organ, abdominal or pelvic wall (T4) 
Treatment planning of UBC is based on distinguishing the superficial tumour (non-muscle invasive tumour, T1-stage or lower) from the invasive tumour (muscle invasive, T2-stage or higher). This is because the treatment options are quite different. On the one hand, transurethral resection (TUR) is performed on patients with superficial tumours. On the other hand, radical cystectomy, radiation therapy, and/or chemotherapy is performed on patients with invasive tumours 
Because the management of urinary bladder cancer is quite different on the basis of the presence of detrusor muscle invasion, preoperative imaging studies are very important to accurately differentiate between the two stages of UBC. MRI is more useful and non-invasive than other diagnostic tools for staging bladder cancer, and a combination of T2-weighted imaging (T2WI) and diffusion-weighted imaging (DWI) is the best for the T-staging of urinary bladder cancer [3, 4, 5]
Superficial tumours with an uninterrupted hypointense submucosal stalk (stage T1 or lower) beneath a C-shaped hyperintense tumour on DWI could be differentiated from invasive tumours without stalks. This finding is defined on DWI as ‘inchworm sign’ because it resembles the characteristic ‘‘inching’’ movement of inchworms. The low signal intensity stalk is one of the characteristic features of pedunculated non-invasive bladder tumours, made of a mixture of edematous submucosa, fibrous tissue, and capillaries. Therefore, an inchworm sign is a simple diagnostic criterion that characterizes only the shape of the tumour signal on DWI and it might provide information on the degree of microinvasion into the muscularis propria [2, 6]
Nevertheless, although most UBC with a stalk and an inchworm sign tend to be stage T1 or lower, there have been reported cases of muscle-invasive tumours showing the ‘‘inchworm sign’’ on DWI [3, 4]
Endoscopic treatment of the described bladder lesion was performed in our patient. In the histological biopsy, fragments of a low-grade inverted urothelial carcinoma were obtained that did not infiltrate the lamina propria or the muscle layer, findings consistent with the expected result and the reason why the patient did not require any other treatment.
Written informed patient consent for publication has been obtained.
 Magers M, López-Beltrán A, Montironi R, et al (2018). Staging of bladder cancer.
 Histopathology 74(1):112-134 (PMID: 30565300)
 Yajima S, Yoshida S, Takahara T, et al (2019). Usefulness of the inchworm sign on DWI for predicting pT1 bladder cancer progression. European Radiology 29:3881–3888 (PMID: 30888482)
 Da-hoon Kim MD, Byung Chul Kang PhD and Jin Chung MD (2020). T1-Staging for Urinary Bladder Cancer with the Stalk and Inchworm Signs with 3.0 Tesla MRI. J Korean Soc Radiol 81(5):1194-1203 (KMID: 2507443)
 Kobayashi S, Koga F, Yoshida S, et al. (2011) Diagnostic performance of diffusion-weighted magnetic resonance imaging in bladder cancer: potential utility of apparent diffusion coefficient values as a biomarker to predict clinical aggressiveness. Eur Radiol 21:2178–2186 (PMID: 21688007)
 Yoshida S, Takahara T, Kwee TC, et al (2017). DWI as an imaging biomarker for bladder cancer. Am J Roentgenol. 208:1218–1228 (PMID: 28245143)
 Arévalo N, Méndez R and Barrera J (2018). "Inchworm sign" in urinary bladder cancer. Abdom Radiol (NY) 43(12):3509-3510 (PMID: 29671008)
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.