DIAGNOSTIC VALUE OF SHEAR-WAVE ELASTOGRAPHY IN THE CHARACTERIZATION OF TESTICULAR LESIONS: INITIAL EXPERIENCE
V.Garriga*, X.Bernal ,JC.Aparicio, L.Ceron, A.Narbona, J.Hernandez, *HOSPITAL JOSEP TRUETA. IDI GIRONA. HOSPITAL GENERAL DE GRANOLLERS
Shear-wave elastography (SWE) is a Non-invasive method that quantifies changes of hardness from the tissue displacement generated by the emission of an acoustic force pulse. The technique has been proposed to differentiate benign lesions from malignant breast lesions.There are few references in the literature of its application in testicular parenchyma evaluation, most of them using ARFI (1,2,3).The difference with the ARFI is that SWE is not a dependent operator technique and gives quantitative values in measurements of velocity (m/s) or pressure (kPa) Young modulus. That makes SWE a reproducible and an objective technique.On the other hand it raises the issue of how to manage the incidental lesions, how often and for how long should be followed or when underwent organ-preserving approach. Among the references in the literatures the hard lesions are more likely to be malignant and a “soft” area may suggest benignity (4). However, exceptions have been described: seminoma and teratocarcinoma have been reported to show soft tissue characteristics and benign entities such scar tissue, cyst, segmental infarct, stromal tumors and epidermoide cyst have been reported to show hard characteristics due to the high cellular consistency (7). SWE allows further evaluation in the field of quantitative imaging of tissular consistency and is proposed as a tool to differentiate lesions with the equivocal B-mode ultrasonography (US) and wrong Color Doppler (CD), specially in granulomatous orchitis, scar lesions and segmental infarct. SWE has also been proposed to assess the effect of varicoceles on testis (6). We present our experience using SWE to characterize different malignant and benign lesions.
1. Technical review: Settings and artifacts for Shear-Wave Elastography (SWE) process
SWE is produced by a highly focused ultrasound radiation; shear wave propagation velocity depends on the stiffness of the tissue (5). To get a reliable value we should start with a “good” 2D image, with no motion artifacts, shadows or noise. Measurement will be obtained from a shear wave box size not bigger that 20 x 20 mm. Box should be placed in the testicular parenchyma at least 10 mm away from the capsule, rete testis, big vessels or any other anatomic fibrous structure. Best option is in the middle of the testis and 5mm away from the tunica albuginea because of limited tissue displacement determined by the fibrous covering(3). We use one shot scan and analyse the twin view. Procedure is well preformed if we get a good speed on the left view, that is an homogeneous color view and a right propagation on the right view, with all wave lines smooth, not necessarily straight, and parallel to each other, FIG1. When quantifying values for normal parenchyma we use four ROIs mesurements and calculate the mean value. The IQR is our indicator of good quality adquisition.
We should avoid fibrous surrounding structures that can give a wrong result of hardness such is the capsule or the rete testis, FIG2.
2.Values of normality
We reviewed 176 adult patients and 20 prepuberal patients with 10-14 H linear probe B-mode Doppler color and SWE. Values of normality were collected in those studies without focal lesions.Mean value of normal testicular parenchyma obtained from a review of 154 adult patients is 2,5 kpa (2,2-3 kpa), with a mean velocity of 0,95m/s (0,92-0,99m/s) , FIG3 . This correlates with previous references in the literature (8).There are some limitations of the tehnique. It is difficult to establish the mean value in prepuberal testis which is affected by many artifacts. Movement and the small size of the testis conditionate variable results most of them with not optimal IQR that no allow to record reproductible results, FIG4.There are some other limitations related to adquisition and tissue heterogenicity, FIG5.
3. Characterization of testicular lesions: Germ-cells Tumors
It is the more frequent tumor, represents 35-50% of germ cell tumors. More than half of the germ cell tumors are composed of more than one type of cells.The histopathology of pure seminoma corresponds to a soft tumor with homogeneous cellularity. This characteristic correlates with discretely high values of SWE. We have recorded values in 7 patients with a mean value of 13kPa (5.9-16.9kPa). Correlation between sonographic image and histopathologic fidings was obtained in 5 patients, FIG6,7,8.
Yolk sac tumor:
Tumour characterized by numerous patterns that recapitulate the yolk sac, allantois and extra embryonic mesenchyme. In children it is the most common testicular neoplasm. Macroscopically pure yolk sac tumors are solid and soft , with a cut-surface somewhat mucoid. We recorded a case of a child with a mixed heterogeneous ecotextures with tiny cystic components with a mean value of 8,4kPa ( 8.2-9,8kPa), FIG 9.
3. Characterization of testicular lesions: Teratoma
It is composed of several types of tissue representing different germinal layers (endoderm, ectoderm and mesoderm). Itmay be composed exclusively of well differentiated, mature tissue or have immature fetal-like tissues. It is generally well circumscribed complex mass with variable degrees of calcifications. When composed only of ectoderm tissue Epidermoide Cyst is the terminology to described the lesion. Keratining and non-keratiningizing squamous epithelium is well defined with a characteristic laminated morphology well reflected in US. That gives the appearane of distinctive laminated morphology with a sharply marginated round or oval mass with a capsule well defined and sometimes calcified. The mass may be hypoechoic but laminations give rise to an “ onion-skin “ or “ target “ appearance, FIG10 . SWE demonstrates in two cases recorded high value, mean of 64 kPa ( 56-91kPa) and 91 kPa ( 89-125kPa) ,FIG11,12, both considered benign lesions.
Dermoid cyst :
It is a mature teratoma with a predominance of one or more cystic lined by keratinizing squamous epithelium with skin appendages . At US it appears as a well defined and heterogeneous lesion corresponding to calcifications, fibrosis and scar formation. SWE demonstrates in one case mean vaue of 116 kPa ( 89-125kPa) .
3.Characterization of testicular lesions: Stromal tumor and Lymphoma
Sex cord/gonadal stroma tumours
Leyding cell tumor is the most frequent non-germinal tumor. It is almost always benign and therefore a control tribute.Very rarely it can be maligne. Preservation surgery can also be considered. Occasionaly, Leyding cell tumor are seen in patients with Klinefelter syndrome. It is generally well defined, encapsulated , 3-5 cm in size. The cut surface is usually homogeneous yellow with hyalinization and calcification focus. At US it appears as well defined hypoechoic small solid mass but may show cystic areas, hemorrhage or necrosis, located in the perifery of the testis. Its sonographic appearance may be indistinguishable from germ cell tumor. Literature reviewed refers a harder appearance in SWE (2). SWE in one patient with a Klinefelter syndrome presented bilateral involvement with mean value of 5kPa ( 4.5-5.3 kPa) FIG13, the other patient correlates with the description with a mean value of 15 kPa (15.1-17.9kPa).
Testicular lymphoma constitutes 2 % of all testicular neoplasm. It presents with uni or bilateral enlargement of scrotum or swelling in the inguinal region. Macroscopically the cut-surface usually reveals poorly demarcated tan, grey and necrotic or hemorrhagic single or multiple nodules or enlargement of testis amd paratesticular tissues and histologu depicts intersticial fibrosis, tubular hyalinization and loss of tubules. The US appearance consist of focal or multifocal hypoechoic lesions that can completely infiltrate the testis but often indistinguishable from that of germ cell tumors(4). CD shows an hypervascular appearance. SWE reveals in one of our patient a mean value of 46 kPa (42-56kPa) a hard lesion probably due to intersticial fibrosis, FIG 15.
3. Characterization of non-tumoral testicular lesions
Granulomatosorchitis : Itis a rarediseasethatmorecommonlyaffectstheepididymisbutcanalsoinvolvethe testis. Infectiousdiseasesuch TBC and sarcoidosisarethe most common causes. The presence of caseation, necrosis, granulomas, fibrosis and calcificationcancauseheteroneneousechogenicity . Itcanalso manifest as multiple, smallhypoechoinodules. Differentationfrommalignanymay be difficult. Ifthereare no associatedsymptomstissuebiopsymay be required. SWE in onepatient whounderwent to orchiectomyshowedincreasedvalues at SWE with a mean of 29 kPa ( 19-39kPa) FIG. 16. Histopathologicspecimendemonstratedinvolvementbymicobacteriumkumamotonense. Anotherpatientwhopresented a well-organizedtuberculous granuloma with fibrosis and calcifcationsshowed a harder lesions as we show in second casewithproved testicular TBC after BCG intravesicaltreatmentwithmeanvalue of 104kPa ( 83-110kPa) FIG17.
Segmental Testicular Infarct: It is an infrequent finding in a patient with acute testicular pain. Predisposing factor included epididymo-orchitis, trauma, vasulitis, surgery or sickle cell disease. US demosntrates an area of mixed echogenicity, wedge or round shape, with poor or absent CD. Differentation between these lesions and neoplasm could be challenging. SWE demonstrates a softer area at the begining due to increase in water content and swelling of the tissue. After one month the lesion appers stiffer due to organization of hemorrage and necrosis and the shrinkage in size of the lesions (10) .We present one case of chronic infarct which shows poor CD with high SWE values with a mean of 44 kPa ( 35-48kPa) ,FIG18. On the other hand testicular torsion is one of the common acute scrotum easy diagnose with US and CD. When testis is torsional the edema, hemorrage and necrosis may also arise the SWE values specially in the border area of the twisted testicle. SWE improves diagnostic confidence as a complementary tool in the diagnosis of acute scrotum (9). We present one case with mean value of 4,1 kPa ( 3,4-4.5kPa) FIG19.
The SWE reflects the relative stiffness of the testis in a real, non-invasive way, differentiating the pathological pathway from the tissue. In combination with gray-sclae and Color Doppler , SWE may supose an increase in sensitivity to differentiate between malignant vs benigne lesions including epidermoide cyst, stromal tumor, granulomatous orchitis, segmental infarction and Leyding cells hyperplasia.It offers special advantage in lesions such as granulomatous orchitis or fibrosis with equivocal CD findings(1) .Even all testicular tumors show an increase in their rigidity compared to the healthy testis, Seminomatous tumors are the tougher than the rest when comparing with stromal tumors. In contrast, benign lesions such as the epidermoid cyst and granulomatous orchitis exhibit more rigid behavior by the associated fibrosis component. The acute phase of testicular ischemia is accompanied by a slight increase in stiffness that progresses as the infarction sets in. The correlation found between the findings in the SWE and the histopathological studies explains the different behavior in each process. In summary SWE may support conventional US in identifying lesions with controversial findings. It can be proposed as an additional tool for the discrimination of focal testicular lesion for planning tissue-sparing surgical enucleation when suspicion for bening lesion or support a
Further studies should be done to prove SWE clinical value, but it can be proposed as an additional tool for the discrimination of focal suspicious testicular lesion to support a “watch and wait” approach or for planning tissue-sparing surgical enucleation.
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