Tsili et al. Journal of Medical Case Reports 2011, 5:169 http://www.jmedicalcasereports.com/content/5/1/169 Page 3 of 4 Figure 3 (a) Transverse DW echo planar image (b = 900 mm2/ s) and the (b) corresponding ADC map. The mass (arrow) appears mainly hypointense on DW images, due to the presence of abundant fibrous part. The ADC value of the fibrous component was 0.86 × 10-3mm2/s. Left hydrocele (long arrow). benign neoplasms; no cases of malignant transformation or local recurrence have been reported [3,4]. MRI of the scrotum as an alternative imaging modality has been proven with satisfactory results in the evalua- tion of scrotal contents [1,2,5-7]. The wide field-of-view, multiplanar capability and high resolution of this techni- que allow the precise demonstration and lesion localiza- tion, thereby distinguishing paratesticular from intratesticular mass lesions [1,2,5-7]. Moreover, tissue signal intensity may prove valuable in characterizing their nature [1,2,5-7]. MR examination of the scrotum in our patient revealed the presence of a sharply-demarcated multilobular paratesticular mass, isointense on T1- weighted images, heterogeneous, but predominantly of very low signal intensity on T2-weighted images. One limitation of the MR protocol used in this study was that it did not include post-contrast images, although the lesion was reported with vascularity on sonographic examination. The hypointensity of the mass on T2- weighted images and the restricted diffusion on ADC maps was suggestive for the presence of fibrous tissue, proved through histology to correspond to the abundant fibrotic component of an adenomatoid tumor of the tunica albuginea. The presence of abundant collagen- producing fibroblastic cells and a dense network of col- lagen fibres cause restriction in the diffusion of the water molecules in fibrotic lesions, as also proved in our patient [8,9]. Patel et al. reported a case of an adenoma- toid tumor of the tunica albuginea evaluated by MRI [3]. The tumor was also of low signal intensity on T2- weighted images, with decreased enhancement after gadolinium administration, when compared to that of normal testicular parenchyma in our report [3]. Differential diagnosis of benign fibromatous paratesti- cular masses, as in our case, should include fibrous pseudotumor. This rare tumor is not a true neoplasm, but a reactive fibrous proliferation of the extratesticular tissues [1,2,10,11]. The majority (75%) of cases arise from the tunica vaginalis, and the remaining from the epididymis, the spermatic cord and the tunica albuginea [1,2,10,11]. MRI findings include signal hypointensity on both T1 and T2-weighted images, a finding strongly suggesting the fibrous nature of the mass. After gadoli- nium administration, little or no enhancement of the tumor has been reported [1,2,10,11]. Conclusion MRI evaluation in our patient provided valuable infor- mation in the pre-operative work-up, by allowing the precise localization of the mass and helping in charac- terizing the benign nature of fibrous paratesticular tumor, by using both the conventional and diffusion MRI. Confirmation of the diagnostic efficacy of MRI examination with prospective studies in unselected scro- tal masses is required. Consent Written informed consent was obtained from the patient for publication of this case report and any accompany- ing images. A copy of the written consent is available for review by the Editor-in-Chief of this journal. Abbreviations ADC: apparent diffusion coefficient; DW: diffusion-weighted; MRI: magnetic resonance imaging.