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Although most {{Main|Ultrasonography of the extratesticular lesions are benign, malignancy does occur; the mosttumors}}common malignant tumors in infants and children are rhabdomyosarcomas. Other malignant tumors include liposarcoma, leiomyosarcoma, malignant fibrous histiocytoma and mesothelioma.<ref namegallery mode="packed" heights="MakTzeng2012150"/> ===Rhabdomyosarcoma===[[File:Scrotal ultrasonography of rhabdomyosarcoma.jpg|thumb|Rhabdomyosarcoma (a) Longituidinal section (composite image) of high resolution ultrasound of a 14 year-old boy shows a well defined hypoechoic extratesticular mass is found in the left scrotum, hydrocele is also present. (b) Color Doppler ultrasound shows that the mass is hypervascular.<ref name="MakTzeng2012"/>]] Rhabdomyosarcoma is the most common tumor of the lower genitourinary tract in children inthe first two decades, it may develop anywhere in the body, and 4% occur in the paratesticularregion which carries a better outcome than lesions elsewhere in the genitourinary tract. Clinically, the patient usually presents with non-specific complaints of a unilateral, painless intrascrotal swelling not associated with fever.<ref name="MakTzeng2012"/> Transillumination test is positive when a hydrocele is present, often resulting in amisdiagnosis of epididymitis, which is more commonly associated with hydrocele.The ultrasound findings of paratesticular rhabdomyosarcoma are variable. It usuallypresents as an echo-poor mass [Fig. 11a] with or without hydrocele. With color Doppler sonography these tumors are generally hypervascular.<ref name="MakTzeng2012"/> ===Mesothelioma===[[File:Scrotal ultrasonography of mesothelioma.jpg|thumb|Mesothelioma arising from the tunica vaginalis. Color Doppler ultrasound demonstrates a well-defined hypoechoic nodule occupying the left epididymal head, with a few areas of color flow demonstrated. The left testis is intact with no focal nodule detected. Hydrocele is also present.<ref name="MakTzeng2012"/>]] Malignant mesothelioma is an uncommon tumor arising in body cavities lined bymesothelium. The majority of these tumors are found in the pleura, peritoneum and lessfrequently pericardium. As the tunica vaginalis is a layer of reflected peritoneum,mesothelioma can occur in the scrotal sac. Although trauma, herniorrhaphy and long termhydrocele have been considered as the predisposing factors for development of malignant mesothelioma, the only wellestablished risk factor is asbestos exposure. Patients withmalignant mesothelioma of the tunica vaginalis frequently have a progressively enlarginghydrocele and less frequently a scrotal mass, rapid re-accumulation of fluid after aspirationraises the suggestion of malignancy.<ref name="MakTzeng2012"/> The reported ultrasound features of mesothelioma of the tunica vaginalis testis are variable.Hydrocele, either simple or complex is present and may be associated with:<ref name="MakTzeng2012"/>#multiple extratesticular papillary projections of mixed echogenicity; #multiple extratesticular nodular masses of increased echogenicity;#focal irregular thickening of the tunica vaginalis testis; (4) a simplehydrocele as the only finding and#A single hypoechoic mass located in the epididymal head. With color Doppler sonography, mesothelioma is hypovascular [Fig. 12]. ===Leiomyoma===[[File:Scrotal ultrasonography of leiomyoma.jpg|thumb|Leiomyoma arising from tunica albuginea. (a) Montage of 2 contiguous sonograms of a 67 year-old man shows a well-defined extratesticular mass with a whorl-shaped echotexture. (b) Color

not associated with echogenic foci in the mass.<ref name="MakTzeng2012"/>]] Leiomyomas are benign neoplasms that may arise from any structure or organ containingsmooth muscle. The majority of genitourinary leiomyomas are found in the renal capsule,but this tumor has also been reported in the epididymis, spermatic cord, and tunicaalbuginea. Scrotal leiomyomas have been reported in patients from the fourth to ninthdecades of life with most presenting during the fifth decade. These tumors are generallyslow growth and asymptomatic. The sonographic features of leiomyomas have beenreported as solid hypoechoic or heterogeneous masses that may or may not containshadowing calcification. Other findings include whorl shaped configuration [Fig. 13a] of the nodule and multiple, narrow areas of shadowing not cast by calcifications [Fig. 13b], but corresponding to transition zones between the various tissue components of the mass are characteristic of leiomyoma and may helpdifferentiate it from other scrotal tumors.<ref name="MakTzeng2012"/> ===Fat containing tumors=======Lipoma====[[File:Scrotal ultrasonography of lipoma.jpg|thumb|Lipoma at spermatic cord and testiscle. (a) Longitudinal scrotal sonography of a 61 year-old patient shows a well defined hyperechoic nodule is seen in the scrotum. (b) Scrotal sonography of the same patient shows a hyper echoic nodule in the left testis, pathology proved that this is a lipoma too.]] Lipoma is the most common nontesticular intrascrotal tumor. It can be divided into 3 typesdepending upon the site of origination and spread:<ref name="MakTzeng2012"/>#Originating in the spermatic cord with spread to the scrotum;#Originating and developing within the cord (most common type) and#Originating and developing within the scrotum. At ultrasound, lipoma is a well–defined, homogeneous, hyperechoic paratesticular lesion ofvarying size [Fig. 14]. The simple finding of an echogenic fatty mass within the inguinalcanal, while suggestive of a lipoma, should also raise a question of fat from the omentumsecondary to an inguinal hernia. However lipomas are well-defined masses, whereasherniated omentum appears to be more elongated and can be traced to the inguinal area,hence scanning along the inguinal canal as well as the scrotum is necessary to make thedifferential diagnosis. Magnetic resonance imaging and computerized tomography arehelpful in doubtful cases.<ref name="MakTzeng2012"/> ====Liposarcoma====Malignant extratesticular tumors are rare. Most of the malignant tumors are solid and havenonspecific features on ultrasonography. The majority of the malignant extratesticulartumors arise from spermatic cord with liposarcoma being the most common in adults. On gross specimen, liposarcoma is a solid, bulky lipomatous tumorwith heterogeneous architecture, often containing areas of calcification. Although the sonographic appearances of liposarcoma are variable and nonspecific, itstill provides a clue about the presence of lipomatous matrix.Echogenic areas correspondingto fat often associated with poor sound transmission and areas of heterogeneousechogenicity corresponding to nonlipomatous component are present. Someliposarcomas may also mimic the sonographic appearance of lipomas [Fig. 16] and herniasthat contain omentum, but lipomas are generally smaller and more homogeneous andhernias are elongated masses that can often be traced back to the inguinal canal. CT and MRimaging are more specific, as they can easily recognize fatty component along with othersoft tissue component more clearly than ultrasound. <gallery widths=180 heights=150>

</gallery> ===Adenomatoid tumor===[[File:Scrotal ultrasonography of adenomatoid tumor at epididymis.jpg|thumb|Adenomatoid tumor at epididymis. A nodule that is isoechoic to the testis is seen occupying nearly the entire epididymal tail.<ref name="MakTzeng2012"/>]] Adenomatoid tumors are the most common tumors of the epididymis and account forapproximately 30% of all paratesticular neoplasms, second only to lipoma. They are usually unilateral, more common on the left side, and usually involve theepididymal tail. Adenomatoid tumor typically occurs in men during the third and fourthdecades of life. Patients usually present with a painless scrotal mass that is smooth, roundand well circumscribed on palpation. They are believed to be of mesothelial origin and areuniversally benign. Their sonographic appearance is that of a round shaped, well-defined,homogeneous mass with echogenicity ranging from hypo- to iso- to hyperechoic.<ref name="MakTzeng2012"/> ===Fibrous pseudotumor===Fibrous pseudotumors, also known as fibromas are thought to be reactive, nonneoplasticlesions. They can occur at any age, about 50% of fibromas are associated with hydrocele, and30% are associated with a history of trauma or inflammation (Akbar et al, 2003). Althoughthe exact cause of this tumor is not completely understood, it is generally believed that theselesions represent a benign reactive proliferation of inflammatory and fibrous tissue, inresponse to chronic irritation.Sonographic evaluation generally shows one or more solid nodules arising from the tunicavaginalis, epididymis, spermatic cord and tunica albuginea [Fig. 18]. A hydrocele is frequentlypresent too. The nodules may appear hypoechoic or hyperechoic, depending on the amount of collagen or fibroblast present.Acoustic shadowing may occur in the absence of calcification due to the dense collagencomponent of this tumor. With color Doppler sonography, a small to moderate amount ofvascularity may be seen [Fig. 19].<ref name="MakTzeng2012"/> <gallery widths=180 heights=150>File:Scrotal ultrasonography of fibrous pseudotumour.jpg|Fig. 18. Fibrous pseudotumor. A homogeneous hypoechoic nodular lesion is seen attached to the tunica associated with minimal amount of hydrocele.<ref name="MakTzeng2012"/>File:Scrotal ultrasonography with Doppler of fibrous pseudotumour.jpg|Fig. 19. Fibrous pseudotumor. With color Doppler, a little vascular flow is seen in this fibrous pseudotumor.<ref name="MakTzeng2012"/></gallery>