Intratesticular Disorders Neoplastic

Germ Cell Tumors (GCT) are the most common neoplasms of the testis. The vast majority of these are malignant. Among the various histologic types, seminoma is the most common to occur as a pure tumor. Most tumors (approximately half of all lesions) are of the mixed variety, containing two or more histologic types. Thus, the non-seminomatous tumors typically include one or more of these types: embryonal carcinoma, teratoma, endodermal sinus tumor, or choriocarcinoma - with or without seminoma. Lesions typically present as a palpable mass, although some aggressive tumors may present with metastatic foci to the lung, bone, or nodal masses.

Most lesions are hypoechoic relative to the background homogeneous, medium-high echogenicity of the testis. Calcifications are seen in at least one third of cases, especially in non-seminomatous tumors.

Management nearly always involves orchiectomy for definitive diagnosis and treatment of the local disease. Seminomas are highly radiosensitive, and in most cases prophylactic radiotherapy to the retroperitoneum is offered. The prognosis is generally good unless there is advanced metastatic disease, such as lung nodules, at the time of presentation [94].

For the non-seminomatous tumors, CT is often used to determine if patients need retroperitoneal lymph node dissection. Patients with (1) nodal involvement (either enlarged on CT, or confirmed on pathologic assessment) and/or (2) hematogenous metastasis are generally treated with chemotherapy. The prognosis for non-seminomatous

* B.J. Wagner tumors is more guarded than that for seminoma, although patients with stage I disease (limited to the scrotum) have five year survival rates approaching 90%.

Gonadal stromal tumors are less common (less than 10% of lesions) and are often incidental findings. Both Leydig cell and Sertoli tumors are occasionally the cause of gy-necomastia. The vast majority of these tumors are benign, but have non-specific grey scale sonographic features. One study reported characteristic peripheral hypervascu-larity in these lesions [95], but it is unlikely that orchiec-tomy could be avoided in most cases because the sono-graphic features do not allow confident exclusion of malignancy nor absolute differentiation from the more common (and more sinister) germ cell tumors.

Lymphoma of the testis is typically seen in older patients than those affected with GCTs, and it is rarely demonstrated in patients without a known diagnosis of systemic lymphoma. Hypoechoic, multifocal (or geographic), bilateral lesions, which often have increased vascularity compared with GCTs, are seen [96].

While not strictly neoplastic, five entities deserve discussion in this context: simple cysts, tubular ectasia, epidermoid cyst, congenital adrenal rests, and testicular microlithiasis (TML).

Simple cysts are typically peripheral, multiple, and contiguous with the tunica albuginea (more central cysts are usually a manifestation of tubular ectasia). These have no malignant potential and are rarely of clinical significance, although they may be palpable and clinically mimic a germ cell tumor. Rarely, they may be complicated by hemorrhage; most cases are easily diagnosed as simple cysts. Features that raise concern for malignancy (and prompt surgical removal), include solitary lesions complicated by internal soft tissue, calcification, or a thick irregular wall.

Tubular ectasia represents a dilatation of the rete testis as it converges along the mediastinum testis. Patients may have a history of prior epididymitis or vasectomy, but most have no specific symptoms. An ovoid or linear area of decreased echogenicity, contiguous with the epididymis, can usually be differentiated from neoplasm based on the pattern of branching anechoic channels [97]. In occasional cases that may mimic neoplasm, T2-weighted MRI will show a hyperintense focus (in contrast to the hypointensity characteristic of most testicular neoplasms), which is often bilateral.

Epidermoid cyst is not considered to be a neoplasm by most authorities. Instead, it is an inclusion cyst, lined by squamous epithelium and filled with keratinized debris. Although it accounts for less than 10% of intratesticular masses, differentiation of the epidermoid cyst from germ cell neoplasm is important in order to avoid radical surgery for this lesion that can, instead, be effectively diagnosed and treated with a more limited procedure (enu-

cleation, sparing the testis). Epidermoid cyst can be recognized in many instances by an 'onion-skin' appearance: alternating concentric rings of hypo- and hypere-chogenicity [98]. A minority of cases will show wall calcification. The absence of Doppler flow may be of some help (the presence of central flow excludes the diagnosis), but one should remember that some neoplasms, especially when small, will not have flow detected sono-graphically. Additionally, the onion-skin appearance is neither sensitive (it is seen in approximately half of cases) nor entirely specific (some neoplasms, including ter-atoma, may rarely have the same feature) [99].

Congenital adrenal rest tumors are seen in patients with poorly-controlled congenital adrenal hyperplasia (CAH). Aberrant adrenal cortical cells migrate with gonadal tissue during fetal development, and may hypertrophy at some point during the disease. The sonographic appearance is extremely variable, but is typically distinguished from malignant germ cell tumor by the multiplicity of the lesions, their eccentricity, and their contiguity with the mediastinum testis. Treatment is glucocorticoid replacement or, rarely, surgery (partial orchiectomy) [100].

Testicular microlithiasis (TML) describes the presence of numerous small (1-2 mm) calcifications scattered throughout the testicular parenchyma. This idiopathic condition is associated with oligospermia in a minority of cases; in most patients this is merely an incidental finding. Although somewhat controversial, most published reports conclude that there is an increased risk of testicular germ cell tumors in patients with TML. For this reason, patients should be carefully screened for coexistent tumors, and followed sonographically at annual intervals for interval development of malignancy [101-103].

Non-neoplastic

Infection typically begins in the epididymis. Epididymo-orchitis is usually a clinical diagnosis; sonography is sometimes used to rule out torsion or progression to abscess. Sonographic findings are often absent, although some patients will show a hydrocele (with or without complicating elements indicating pyocele). There may also be increased Doppler flow to the epididymis. Progression to involvement of the testis occurs in a minority of cases, and may result in abscess formation or infarction.

Ischemia/infarction may result from torsion or less commonly from a variety of other causes (including vasculi-tis, diabetes, or orchitis). Patients with torsion typically have an acute clinical presentation with severe unilateral scrotal pain, often following minor trauma or physical exertion. The typical finding is an asymmetric decrease in color or amplitude (power) Doppler signal to the symptomatic side. However, subtle variations of arterial spectral Doppler waveforms may be seen early, including ab sence of the dicrotic notch and/or increased resistance (decreased or absent diastolic flow) [104]. The latter finding may also be seen in early stages of torsion when venous flow is altered but arterial flow is still seen by color Doppler.

Emergent surgery is indicated to detorse and save the testis; however, when grey scale findings are present, including heterogeneity and decreased echogenicity, the ischemia has almost always progressed to infarction [105]. At this point, testicular salvage is not possible.

Important pitfalls in Doppler evaluation must be recognized in order to avoid misdiagnosis. The examiner must be careful not to alter Doppler settings (gain, scale, etc.) when comparing the normal (asymptomatic) testis to the painful side. One must also remember that paratestic-ular tissues may show reactive hyperemia, despite the absence (or significant decrease) in Doppler flow to the testis itself. Focal infarction has a variety of causes with a common pathway of microvasculitis and will show regional wedge-shaped areas of decreased perfusion, often with adjacent hyperemia [106].

Sarcoidosis is an unusual cause of a scrotal mass, and may rarely be the presenting site of disease in some patients. The pattern of multiple hypoechoic intratesticular masses associated with epididymal enlargement and heterogeneity is characteristic, although it may also be seen in lymphoma.

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