Rare presentations of testicular germ cell tumors: a pictorial multiparametric imaging review
Rare presentations of testicular germ cell tumors: a pictorial multiparametric imaging review
C. Balasa, Septimiu Popescu, Emmanuel Arama, Chun Wah So, Cedric Lebacle, Sophie Ferlicot, Laurence Rocher
To review the histopathologic subtypes of testes germ-cell tumors. To remind the classical imaging aspects of seminomatous and non-seminatomatous germ cell tumours. To illustrate the multiparametric ultrasound and MRI aspects of uncommon appearances of germ cell tumors.
Testicular germ cell tumors (TGCTs) are the most common testicular neoplasms, occuring in young and middle-aged men and they account for 95% of testicular tumors, with the remainder being due to lymphoma and other less common pathologies. The overall incidence of germ cell tumors is increasing, but the exact reasons for this are uncertain. They demonstrate diverse oncogenesis, pathologic findings and clinical-biologic behaviors and the updated 2022 World Health Organization (WHO) classification system has substantial diagnostic and treatment implications. They have since been categorized into postpubertal tumors—including those derived from a “germ cell neoplasia in situ” (GCNIS)—and prepubertal tumors, including those unrelated to GCNIS. The first category includes pure seminomas and nonseminomatous germ-cell tumors (NSGCTs), which may be pure or mixed tumors. Mixed tumors show variable proportions of embryonal carcinoma, yolk sac tumors, postpubertal teratomas, and choriocarcinomas. This category also includes regressed germ-cell tumors (“burned-out” tumor (BOT)). TGCTs not derived from GCNIS include spermatocytic tumors, prepubertal-type teratomas (e.g., dermoid and epidermoid cysts, and well-differentiated neuroendocrine tumors), prepubertal mixed teratoma and yolk sac tumors, and prepubertal yolk sac tumors. Seminoma is considered a GCNIS-derived tumor. Before the 2016 WHO classification, spermatocytic seminoma was considered a subtype of seminoma; however, since it lacks association with GCNIS, it is now considered a separate entity unrelated to seminoma. Seminomas typically present as a unilateral homogenously hypoechoic lesion with transnodular vascularity. Cystic areas and calcifications are uncommon. NSGCTs tend to be ill-defined heterogeneous lesions with areas of necrosis, hemorrhage, cystic change and calcifications. At MRI, seminomas are homogeneously T1 isointense and T2 hypointense, with well-circumscribed or lobulated margins. On diffusion-weighted MRI, marked restricted diffusion secondary to increased cellularity and underlying inflammation can be seen; bandlike hyperenhancement of fibrovascular septa is characteristic of GCNIS. In comparison, NSGCTs are markedly heterogeneous with a hypointense pseudocapsule at T2-weighted MRI. They may show heterogeneous areas at T1- and T2-weighted MRI that are secondary to the presence of cystic change, hemorrhage, or necrosis. Although the ultrasound and MRI appearance of typical unique germ cell lesions has been thoroughly described previously, there are several other rare potential presenting situations that we aim to illustrate, such as: - Burned out tumours The spontaneous regression of primary testicular germ-cell tumours is a rare event whose mechanisms have yet to be understood, resulting in its partial or complete replacement by a patch of fibrosis. Such lesions have been commonly considered burned-out testicular tumours (BOTTs) and are commonly diagnosed in symptomatic metastatic patients. The typical ultrasound appearance of a BOTT has been described as a hypoechoic, poorly delineated, hypovascular nodular area, with clustered microliths and macrocalcifications frequently encountered in peripheral areas and focal areas of increased stiffness on SWE. US findings may be insufficient to prompt orchiectomy as BOTTs can be confused with benign lesions, most avascular or hypovascular testes lesions being benign, including segmental testicular infarction, epidermoid cysts and hematomas. If a BOTT is suspected on ultrasound, then the presence of an area of reduced enhancement with increased ADC values on MRI makes the diagnosis very likely. These elevated ADC values should not be taken as a sign of benignity, even if testicular cancer usually appears as a restrictive lesion on diffusion-weighted sequences (low ADC values). (Fig. 1, 2, 3 and 4) To the best of our knowledge, our first case is the only report of an increase in testis volume associated with a diffuse BOTT, as burn out lesions are generally encountered in hypotrophic testes. - Extragonadal germ cell tumors Extragonadal germ cell tumors (EGCTs) with no identifiable testis nodule (Fig. 5 and 6) often develop in midline structures and represent 1% to 5% of all germ cell tumors (GCTs). Morphological type includes mature/immature teratoma, seminoma, yolk sac tumor, embryonal carcinoma, choriocarcinoma and mixed gonadal GCTs. Their anatomic distribution varies widely and includes the mediastinum, sacrococcygeal region, neck, retroperitoneum and other rare anatomic sites. - Large or diffusely infiltrating lesions Occasionally, germ-cell tumors may occupy the entire pulp (Fig. 7) or interrupt the albuginea (Fig. 8), infiltrating the epididymis or the tunica vaginalis (T2 lesions) or the spermatic cord (T3). - Purely cystic multilocular lesions Although there have been very rare reports of mucinous or serous cystadenoma or hemangiolymphangioma of the testis, multilocular cystic lesions of the testis with no solid components with thick enhancing septa and loculi with variable echogenicity and signal intensity should remain conspicuous for teratoma, as in Fig.9. - Post-pubertal cystic teratomas with echoic contents Mature teratomas should be considered in patients presenting with non-spherical cystic lesions with heterogeneous echoes in the fluid, representing a mixture of mucinous or sebaceous material, with or without hair follicles. (Fig.10) - Partially cystic seminomas While cystic areas are often encountered in NGCTS and atypical in seminomas, up to ten percent of seminomas may present with varying degrees of cystic change (Fig.11), which some investigators attribute to infiltration and obstruction of the rete testis by tumor. In most reported cases, the diffuse cystic architecture related to the presence of syncytiotrophoblast giant cells that had undergone massive pseudocystic change. - Torsion and hemorrhage, The commonest presentation of a testicular neoplasm is a hard, painless, palpable slow-growing mass. Acute painful presentations of testicular neoplasms have a varying rate of incidence, between 0.01% and 10%, of all cases, which illustrates the scarcity of such a presentation among the overall incidence of testicular neoplasms in the general male population. Preoperative multiparametric ultrasound can thoroughly identify and characterize the underlying lesion and guides surgical approach. In our case, the intraoperative visual assessment of the testis during the emergency detorsion and orchidopexy didn’t identify the mass and the large mixed GCT with 5 components (yolk sac tumor, post-pubertal teratoma, embryonal cell carcinoma, choriocarcinoma and seminoma) was only discovered on the follow up ultrasound (Fig. 12). - Necrotic tumors Entirely or mostly necrotic testicular tumors present a diagnostic imaging and histopathological challenge and should be distinguished from hematoma, segmental infarction and abscesses. Patients with testicular infarction or hematoma usually present with acute pain rather than a painless palpable mass. If the diagnosis is uncertain on the basis of the imaging features and clinical presentation, short-term follow-up imaging in 2–4 weeks may be helpful because hematomas usually decrease in size over time, and areas of infarction will become more avascular and more hypoechoic over time. MRI and CEUS prove very helpful in differentiating tumors from nonenhancing benign entities as these lesions do not enhance, but the surrounding parenchyma may show avid enhancement, whereas necrotic tumors generally retain some solid enhancing areas (Fig. 13 and 14). - Extensive calcifications The presence on ultrasound of a densely calcified solitary testicular mass carries a differential diagnosis of primarily benign pathologies, including spermatic granuloma, large-cell calcifying Sertoli cell tumour, trauma, tuberculosis, filariasis, calcified Leydig cell tumour, but non seminomatous germ-cell tumors, mainly teratomas, may also display such features. Mature teratoma in children is often benign, but teratoma in adults, regardless of age, should be considered as malignant. Teratomas consist of elements derived from more than one germ cell layer (endoderm, mesoderm and/or ectoderm). Teratomas generally appear as well-circumscribed complex masses on ultrasound. Echogenic foci representing calcification, cartilage, immature bone and fibrosis are commonly seen. (Fig. 15 and 16) - Iso/hyperechoic lesions Choriocarcinomas and embryonal cell carcinomas (Fig. 17) occasionally appear iso or hyperechoic and should be distinguished from benign lesions, such as hematomas, abscesses and atypical Leydig-cell tumors. Multiparametric ultrasound and MRI are highly contributive, as NGCTS will display intralesional increased vascularity and stiffness, whereas benign lesions appear either avascular (hematomas and abscesses) or present a mainly peripheral circumferential vascularization with moderately increased stiffness (LCTs). A feeding vessel is identified on CEUS in some Leydig-cell tumors and their enhancement follows a type 3 time-intensity curve, with avid early enhancement and late wash-out on MRI, whereas NGCTS will have significantly lower ADC values and follow a type 2 enhancement curve. - Invasive tumors with extratesticular development mimicking purely extratesticular lesions Occasionally, germ-cell tumors may display extratesticular growth and be mistaken for an extratesticular lesion. As in our case, MRI is highly useful in individualising the intratesticular suspicious lesion non visible on ultrasound and the thin parenchymal bridge uniting it to the extratesticular component (Fig. 18 and 19). - Bilateral lesions Bilateral germ cell tumors of the testicles are rare, representing only 1 % of all new cases of testicular cancer, around 30 % of these occurring synchronously. Interestingly, bilateral synchronous testicular lesions share the same histopathological type, most of them being seminomas, as in our case (Fig. 20).
Fig.1 32 year-old patient with azoospermia referred for a fertility work up Diffuse hypoechoic infiltrating lesion of the right testicular parenchyma associated with an increase in testis volume, clustered microliths and macrocalcifications (a and b), displaying hypovascularity (c) and moderately increased stiffness (d)
Fig.2 MR in the same patient as Fig. 1 T2 hypointense infiltrating mass occupying a large part of the right testis (a and b), with no increase in intensity on diffusion weighted imaging, high ADC values (c and d) and reduced perfusion with a type I time-intensity enhancement curve (g and h)
Fig.3 CT findings in the same patient as the previous 2 images Retroperitoneal subcentimetric lymph node on initial staging CT (a), increasing in dimensions one month post orchidectomy (b) Robotic lymphadenectomy was performed and histopathological analysis revealed active seminoma
Fig.4 A hypoechoic ill-defined hypovascular area (a and b), with increased stiffness (c) and associated macrocalcifications was identified in the left testis of this 57 year-old patient presenting with mediastinal adenopathy No circumscribed nodule could be identified MRI was highly contributive, as although there wasn’t any visible nodule, the presence of a T2-wi hyperintense (e, f), faintly enhancing subalbugineal area (i, j), with increased ADC values (h) was in favour of a burn out tumor Pulp signal asymmetry between the testes may also be noted, with (d, e), with signal increase on T2-wi and ADC hypospermatogenesis
Fig.5 49-old patient referred for a probable retroperitoneal seminoma On ultrasound the testes were hypotrophic with extensive bilateral microlithiasis and no asymmetry in vascularity or stiffness (a, b, c and d) An underlying lesion would be easily missed, masked by the microlithiasis Although there was no focal lesion on T2-wi (e, f), MRI once more managed to identify the left testicular hypoenhancing area (h and i) with high ADC values (g, 2,074*10-3 mm2/s)
Fig.6 Same patient as previous figure A retroperitoneal hyperfixating mass was visible on CT and PET-CT (a, b and c)
Fig.7 28 year-old patient with a history of left orchidectomy for a non-seminomatous germ cell tumor in 2015 referred for a recent increase in the right testis volume with a nodular sensitive induration The entire remaining right testis was occupied by a hypoechoic heterogenous intensely vascularized stiff mass with associated microliths (a, b and c) Similar findings on MRI, the T2-hypointense mass occupying almost the entire pulp (d, e), with increased cellularity (f) and necrotic areas post contrast (g, h) in favour of recurrence
Fig.8 Very large left testis seminoma in a 49 year-old patient presenting with scrotal pain and enlargement, initially mistaken for epididymo-orchitis There are multiple hypoechoic nodules and a large extratesticular hypervascular very stiff component with albugineal interruption and epididymal invasion (a, b, c and d). MRI allows for a more accurate characterization of this T2-wi hypointense highly cellular lesion (f, e and j), interrupting the tunica albuginea with tumor spiculi extending towards the tunica vaginalis (f and h), infiltration of the epididymis and of the left spermatic cord (i)
Fig.9 Multilocular cystic lesion occupying almost entirely the left testis of a 27 year-old patient (a and b) Certain cystic spaces have a moderately hyperechoic content and the thick septa displayed intense enhancement on contrast-enhanced ultrasound (c and d) Some loculi display a T1-w hyperintense proteinaceous or hemorrhagic content (g) and no solid area was visible
Fig.10 Ultrasound examination performed in a 61 year-old patient with left orchitis revealed a bilocular cystic lesion, with a partially echoic avascular content, irregular contours, peripheral calcifications and increased stiffness (a, b, c and d). On MRI, the lesion was cystic, with a T2-wi partially hypointense component with no diffusion on restriction and a small enhancing mural nodule (e, f, g and h)
Fig.11 45 year-old male patient having recently palpated a right testis lesion which proved to be a pure seminoma Two components were visible on ultrasound: a cystic well defined nodular component with a large solid portion (a, b and c) and a crescent-shaped hypoechoic peripheral component with moderately increased stiffness (d, mean value of 14.8 kPa) The solid portion and the peripheral T2-wi hypointense crescent-shaped component (e, f) showed increased cellularity on diffusion weighted images (g, h) and moderate enhancement (i, j)
Fig.12 Follow-up ultrasound several weeks post torsion and orchidopexy with no pre-operative ultrasound revealed a very large heterogenous right testis mass with cystic spaces (a, b) in a 17 year-old patient. The cystic spaces demonstrate multiple fluid-fluid hemorrhagic levels (c, d, e, f), better visible on MRI The patient had a history of left testicular cryptorchidism and extensive microlithiasis in the peri-tumoral pulp could be observed
Fig.13. Almost completely necrotic lesion in 39 year-old male presenting with acute onset intense right testis pain mimicking torsion The lesion was initially mistaken for a heterogenous necrotic area post torsion (a, b) but ultrasensitive color Doppler (c) and contrast-enhanced ultrasound (d) detected some rare vascularized solid areas Fig.14. Similar findings on MRI in the same patient The right testis was almost entirely occupied by a large heterogenous lesion with T2-wi hypointense and T1-wi hyperintense hemorrhagic areas (a, b, c) with artefacts on diffusion-weighted imaging (e, f) and a small solid enhancing area (d, g) Ipsilateral hydrocele and oedematous infiltration of the spermatic cord (h) were also visible Pathology findings were in favour of an NSGCT with over 90% necrosis, the only identifiable component being teratoma Fig.15. 44 year-old patient with oligoasthenoteratozoospermia referred for a second opinion on a left testis nodule discovered during fertility work-up A heterogenous vascularized left testicular lesion with peripheral macrocalcifications (a, b), peripheral uptake on contrast-enhanced ultrasound (c) and highly increased stiffness (d) was identified Fig.16. MRI findings in the same patient as in Fig.15 The left upper pole testicular lesion also has a heterogenous appearance on MRI, with a thick T2-wi hypointense calcified rim (a,b), a T1-wi hyperintense proteinaceous or hemorrhagic content (c), low ADC values (d, e) and mainly peripheral enhancement (f) Pathology findings were in favour of a teratoma. Fig. 17. Embryonal cell carcinoma in a 20 year-old patient with recent onset of scrotal pain with a right lower pole testicular isoechoic hypervascular lesion (a, b and c) with highly increased stiffness (119.6 kPa) The lesion appeared heterogenous on MRI, with T2-wi hyperintense areas and satellite nodules (e, f, g) and a type 2 enhancement curve (j) Fig. 18. Left scrotal mass observed by a 34 year-old patient for the past 3 years, having recently demonstrated a rapid increase in dimensions Hypoechoic vascularized mass (a, b) with considerably increased stiffness (c) (mean value of 33.6 kPa) and intense uptake on contrast-enhanced ultrasound (d) mimicking a purely extratesticular lesion. There was a doubt concerning the existence of a thin parenchymal band connecting the lesion to the ipsilateral testis Fig. 19. . MRI in the same patient as in Fig. 18 confirmed the presence of an associated left lower pole intratesticular lesion with extratesticular development, which was a histologically-proven seminoma The extratesticular component of the lesion was hypointense on T2-weighted images, showed restricted diffusion (mean ADC value of 0.5x10−3 m2/s ) and a type II time-signal intensity enhancement curve (the violet curve corresponds to the extratesticular lesion, the orange curve to the intratesticular component, with the yellow curve corresponding to the contralateral testicular parenchyma) Fig. 20. 32 year-old patient with right scrotal discomfort referred for a second opinion on bilateral lesions A large hypoechoic homogenous highly vascularized stiff lesion (mean stiffness up to 48 kPa on the right) (a, b, c) occupying almost the entire right testis and multiple homogenous hypoechoic left testicular nodules with the same characteristics were visible on ultrasound (d, e) Bilateral microlithiasis was also present MRI depicted the true extent of the T2-wi hypointense bilateral (f, g), hypercellular lesions (h, i) with progressive uptake and enhancing fibrovascular bands (j) in favour of synchronous seminoma
While radiologists are widely familiar with the typical imaging features of seminomatous and non-seminomatous testicular germ cell tumours, there are a certain number of unusual presenting aspects that might hinder the diagnosis, especially in an acute setting. In such cases, multiparametric ultrasound and MRI allow for a more accurate tumor type prediction, especially in non seminomatous GCTs.