a 34-year - old man with painless right scrotal swelling , first noticed four months earlier , was admitted to our hospital . the patient had no history of scrotal trauma , voiding difficulty , other genitourinary diseases or weight loss . physical examination showed that the right side of the scrotum was noticeably enlarged , without tenderness . laboratory studies were unremarkable , with normal levels of alpha - fetoprotein ( 1.70 ng / ml ; normal range : < 20 ng / ml ) and beta - human chorionic gonadotropin ( 3.42 miu / nl ; normal range : < 5 miu / nl ) . under the impression of right epididymo - orchitis , scrotal us revealed a well - defined heterogeneous hypoechoic intratesticular lesion of the right testis , with large hydrocele and diffuse irregular epididymal swelling . also noted were slightly heterogeneous echogenic nodular projections attached to the inner scrotal wall ( fig . for further evaluation , mr imaging was performed , and this demonstrated nodules in the testis , epididymis and inner scrotal wall . the nodules were isointense on t1-weighted images and slightly hyperintense on t2-weighted images . t2-weighted imaging of the intratesticular lesion revealed a low - signal - intensity rim . after infusion of gadopentetate dimeglumine ( gd ) ( magnevist ; berlex , wayne , n.j . , u.s.a . ) , the peripheral portions of these nodules were markedly enhanced ( fig . 1b - e ) . because malignancy was suspected , the patient underwent right radical orchiectomy , and right hydrocele with testis was dissected out without difficulty . on pathologic examination of the resected specimen , variable - sized multiple nodules were seen on the surface of the tunica vaginalis and albuginea ; the largest one was attached to the posterolateral portion of the testis . microscopic examination revealed that the nodules were confined to the tunica vaginalis and albuginea , without penetrating the testis , and between this and the nodules there was a clear plane of separation ( fig . the tumor cells were oval , or round to elongated , with occasional longitudinal nuclear grooves and call - exner bodies , and mitosis was frequently observed ( nine mitoses / ten high - power fields , on average ) . a comparison of the microscopic findings and those of mr imaging indicated that the hypointense rim seen at the periphery of the nodules on t2-weighted images corresponded with intact tunica albuginea . although granulosa cell tumor is the most common sexcord stromal tumor to occur in the ovary , it is extremely rare in the testis and its origin is poorly understood . to the best of our knowledge , the literature in english is limited to only 19 cases of adult granulosa cell tumor of the testis ( 10 ) . we are aware of only two previous reports of the us findings of adult - type testicular granulosa cell tumor , and both of these described the tumor as a well - defined hypoechoic testicular mass ( 11 , 12 ) . in our case , the tumor appeared to arise from the scrotal tunics , an unusual location for a sex - cord stromal tumor . it was , however , because of the presence of typical large indented nuclei with longitudinal nuclear grooves and call - exner bodies , as well as positive immunoreactivity for inhibin , keratin and vimentin , that granulosa cell tumor was diagnosed ( 13 ) . fourteen percent of all paratesticular tumors arise from the scrotal tunics and among these , benign fibroma , representing a fibrous reaction to chronic periorchitis , is the most common lesion ( 14 ) . although granulosa cell tumor arising from the scrotal tunics has not been previously reported , extratesticular sex - cord stromal tumor in the pelvis has been described ( 9 ) . the suggested explanation is that the tumor originated in a residual part of the primitive gonad or a third undescended testis which was completely destroyed by the process , and we believe that in our case the same explanation is possible . pathologic examination indicated that this tumor had originated from and was confined to the scrotal tunics . nevertheless , because the largest nodule was deeply invaginated into the testis , displacing the epididymis , which was compressed and not visualized , the location of this tumor - according to the findings of us and mr imaging - was intratesticular and epididymal . it was because the main lesion was in the testis and epididymis , and multiple small nodules were attached to the inner scrotal wall , that malignancy was suspected . on the other hand , because of extensive hydrocele , the lesion also mimicked an inflammatory condition such as tuberculous epididymo - orchitis . the only clue to the origin of the mass was the low - signal - intensity rim between the lesion and the testis revealed by t2-weighted imaging . to our knowledge , this is the first reported case of paratesticular granulosa cell tumor , and it would therefore be premature to state that the us and mr features of our case are specific to granulosa cell tumor of the scrotal tunics . although the formulation of a treatment plan might not require specific diagnosis , we suggest that the presence of a mass seen as an intratesticular lesion associated with multiple enhancing nodules attached to scrotal tunics indicates the possibility of a paratesticular tumor , and that granulosa cell tumor should be included in the differential diagnosis . we believe that mr imaging findings of a peripheral low - signal - intensity rim on a t2-weighted image might help determine the origin of the mass .