the primary type is caused by the breakdown of endogenous lipids and the secondary type by injection of exogenous foreign bodies . foreign materials , including silicone , paraffin , mineral oil , metallic mercury , petroleum jelly , vaseline , and cod liver oil have been used to provide an improvement in penile shaft contour and dimensions . arthaud et al . , reported the first case of liquid silicone injected to the penis in 1973 , on one subject who had an injection of silicone from a nonprofessional person . liquid injectable silicone for penile augmentation may have debilitating effects , requiring surgical intervention to correct complications . although sonography represents the primary modality for cross - sectional imaging of the penis , magnetic resonance imaging ( mri ) may provide important diagnostic information in the investigation of penile pathology , especially in cases of inconclusive or nondiagnostic sonographic findings . recently , functional mri , including diffusion - weighted imaging ( dwi ) , magnetization transfer imaging ( mti ) , and dynamic contrast - enhanced ( dce ) mri have been used in the interpretation of scrotal diseases . to our knowledge , no reports regarding these techniques in the evaluation of penile diseases exist in the english literature . herein , we present the mri findings of a silicone - induced penile lipogranuloma . a multiparametric mri protocol was used , including dwi , mti , and dce - mri . a 52-year - old man was referred to the urology department with significant enlargement of the penis and sexual dysfunction of 1-year duration . the patient reported a history of subcutaneous injection of liquid silicone in the penis by a nonmedical practitioner , 10 years ago . clinical examination revealed large , painless enlargement of the penile shaft due to the presence of a hard mass invading the skin and the subcutaneous tissues , but not the corpora cavernosae . mri examination was done on a 1.5-t system , with the penis in the flaccid state . the mr protocol included axial spin - echo t1-weighted sequences , fast spin - echo t2-weighted sequences in the three orthogonal planes and transverse dw sequences with b - values of 0 and 900 s / mm . mti was followed in the same plane . magnetization transfer ratio ( mtr ) was calculated from the following equation : where , sim and sio refer to signal intensities with and without the saturation pulse , respectively . after a rapid injection of gadopentetate dimeglumine , sagittal dce subtraction mris were also obtained . a heterogeneous , ill - defined mass involving the subcutaneous tissues around the penis and extending into the intertesticular and retrotesticular region were detected [ figure 1 ] . the lesion was asymmetrically y - shaped with the arms of y around corpora carvenosae , slightly hyperintense , and extremely hypointense on t1- and t2-weighted images [ figure 1a ] , respectively when compared to the penile shaft . the mean adc was 1.53  10 mm / s [ figure 1b ] , similar to that of corpora carvenosae and suggestive of benignity . mtis showed the very low signal intensity of the mass , with a mean mtr of 67% , suggestive of the presence of macromolecules [ figure 1c and d ] . on dynamic imaging , the lesion enhanced strongly and heterogeneously , with an initial upstroke , followed by gradual increase of enhancement in late postcontrast phase [ figure 1e ] . both the corpora cavernosae and the corpus spongiosum were normal , with intact tunica albuginea . based on mri findings and the clinical history , the diagnosis of silicone - induced penile lipogranuloma was strongly suggested , and the patient was referred for surgical excision of the lesion . 52-year - old man with silicone - induced penile sclerosing lipogranuloma . ( a ) sagittal t2-weighted image of the penis demonstrates heterogeneous lesion , with ill - defined margins surrounding the penis . the mass ( arrowheads ) was mainly of low signal intensity on t2-weighted images , a finding suggestive of the presence of fibrous tissue . ( b ) transverse apparent diffusion coefficient map ( b = 900 mm / s ) shows heterogeneous mass ( arrow ) surrounding the penile shaft . the lesion appears mainly isointense when compared to the normal corpora cavernosa ( long arrow ) . the apparent diffusion coefficient value of the mass was 1.53  10 mm / s ( right corpus cavernosum : 1.49  10 mm / s ; left corpus cavernosum : 1.60  10 mm / s ) . transverse three - dimensional gradient - echo images acquired ( c ) without and ( d ) with the application of the magnetization transfers pulse . the magnetization transfer signal of the mass lesion ( arrowhead ) was qualitatively lower than that of the corpora cavernosa ( arrow ) . ( e ) time - signal intensity curve of the lesion shows an initial upstroke after which the signal intensity gradually increases in the late contrast - enhanced phase . during surgery the lesion was solid and white , invading the skin , the subcutaneous tissues , and the dartos muscle of the penis . histopathological examination demonstrated vacuoles of variable size corresponding to exogeneous substance , embedded in collageneous stroma . the patient had an uneventful recovery and was advised to return for follow - up 2 months after surgery . histopathologic evaluation of the excised tissue reveals vacuoles of variable size in the dermis corresponding to exogeneous substance . multinucleated giant cells and abundant fibrosis is seen around the vacuoles ( hematoxylin and eosin stain , magnification 20 ) . penile sclerosing lipogranuloma is a granulomatous reaction that occurs after injury of the adipose tissue . the secondary type of the disease is caused by foreign body injections directly into the penis , such as silicone , paraffin oil , paraffin balm , and mineral oils . secondary penile sclerosing lipogranuloma usually requires an aggressive treatment including partial or total excision of granulomas , with or without reconstructive skin flaps depending on the extent of excision . an imaging technique accurately characterizing and assessing the extent of the disease would be valuable in the appropriate preoperative planning of these patients . mri is now increasingly used as either a problem - solving tool in cases of indeterminate sonographic findings or as a primary imaging modality in the evaluation of penile diseases . specifically , mri has been proved useful in the differentiation between benign and malignant penile lesions and in defining the extent of inflammatory processes and traumatic injuries . it is also considered the most accurate imaging technique in the assessment of primary penile carcinomas . motoori et al . , described the mri findings of a primary scrlerosing lipogranuloma of the male genitalia in a 55-year - old man . the lesion was symmetrically y - shaped , with the arms of the y surrounding the penile shaft . the mass showed similar and moderately high signal intensity when compared to muscles on t1- and t2-weighted images , respectively , with irregular enhancement after gadolinium administration . small areas within the lesion , hyperintense on t2-weighted sequences , without contrast enhancement , suggested the presence of cystic or necrotic parts . the mass demonstrated an ill - defined symmetrical y - shape , situated just beneath the corpus spongiosum with the arms of the y around the penile shaft . the lesion was mainly isointense on t1-weighted images , strongly enhancing , with low signal intensity on t2-weighted images , the latter related to the presence of fibrous tissue . an asymmetrically y - shaped mass surrounding the carvenosal bodies and extending into the scrotum was revealed in our patient . the hypointensity of the mass on t2-weighted sequences was suggestive of the presence of fibrous tissue , as subsequently proved on pathology and it is considered an important diagnostic feature in differentiating this entity from malignancy . lesion detection and characterization on dwi is mainly dependent on the extent of tissue cellularity , and increased cellularity is associated with restricted diffusion and reduced adc . the adc values of malignancies are usually lower than those of benign lesions or normal tissues . in this case , no areas of restricted diffusion were identified within the mass , and the adc was similar to that of normal corpora cavernosae , findings strongly suggestive of benignity . mti sequences offer a different image contrast compared to t1- and t2-weighted images . in conventional mris , tissue contrast depends mainly on the presence of free protons , whereas , on mtis , the signal is determined by the restricted macromolecular protons . the mt phenomenon is quantified by the mtr . tissues containing macromolecules , a classical example is fibrous tissue , transfer magnetization more efficiently detected as hypointense on mtis , with high mtr , as in this patient . dce - mri evaluates the kinetics of the distribution of the paramagnetic contrast medium in the micro - vessels and the interstitial spaces of the tissues used . malignancies usually present with the rapid uptake of the contrast medium , followed by washout in the delayed phase , whereas benign lesions often enhance strongly and rapidly , followed by either a plateau or gradual increase of enhancement in the late post - contrast phase . although , there are no reports on the dce - mri characteristics of penile lesions in the english literature , penile lipogranuloma in this case enhanced intensely , followed by a gradual increase of enhancement in the late post - contrast phase , findings that could suggest the benign nature of the lesion . mri examination using both morphologic and functional data provided valuable information in the preoperative planning in our case , by estimating the precise extent of the mass and helping in the characterization of the benign nature of disease .
sclerosing lipogranuloma is a rare benign disease , representing a peculiar granulomatous reaction of fatty tissue . 
 the majority of cases are secondary to injection of exogenous foreign bodies , such as silicone , paraffin , mineral , or vegetable oils . to the best of our knowledge , 
 we present the first case of a silicone - induced penile lipogranuloma in a 52-year - old man evaluated with a multiparametric magnetic resonance imaging ( mri ) protocol , including diffusion - weighted imaging , magnetization transfer imaging , and dynamic contrast - enhanced mri . 
 mri of the penis by combining both conventional and functional information represents an important imaging tool in the preoperative workup of silicone - induced penile lipogranuloma .