Testicular seminomas are the most common testicular tumors and account for ~45% of all primary testicular tumors. This article concerns itself only with testicular seminomas, however, seminomas can arise outside of the testicle most often within the anterior mediastinum, e.g. anterior mediastinal germ cell tumors.
Testicular germ cell tumors account for around 1-2% of all malignancies in males up to the age of 65, but they are the most common nonhematologic malignancy in males 15-49 years old. Approximately 50% of germ cell tumors are seminomas.
A higher frequency amongst Caucasians compared with African Americans has been observed (9:1) ref required.
undescended testis is the major risk factor for testicular germ cell tumors
- 10-40x increased risk
- ~10% of tumors are associated with undescended testis
- increased risk in the contralateral normally descended testis
- a previous tumor in the contralateral testis
- a family history of testicular germ cell tumor
- testicular microlithiasis: controversial risk factor, although some sources claim an approximately 8 times increased risk 2
- other risk factors include infections such as HIV, mumps, orchitis, and history of trauma or organ transplant immunosuppression
The most common presentation is with a painless testicular mass although some 45% will report a degree of testicular discomfort. Bilateral tumors are rare (~2%) and are almost always asynchronous 1. Diagnosis following trauma is common as it draws the patient’s attention to the lump. Back pain, abdominal discomfort or abdominal mass may be a presenting feature in the 25% of patients who have retroperitoneal nodal metastases 3. Presentation with distant or extranodal metastases is rare (~5%).
Seminoma by definition must be pure seminoma on histology and not associated with an elevated serum alpha-fetoprotein (AFP). If either of these criteria is not met then, the tumor must be classified as non-seminomatous and managed accordingly. Uncommonly (15%) b-HCG may be slightly elevated. Pure seminomas are subdivided into three histological subtypes:
- classic: 85%, infrequent mitoses; monotonous sheet of large cells with abundant cytoplasm and round hyperchromatic nuclei, prominent nucleoli
- anaplastic: 10%, ≥3 mitotic figures per high-power field
- spermatocytic: 5%, older male patients above 60 years old, rarely metastasise; well-differentiated with cells resembling secondary spermatids
On gross examination, seminomas are pale grey to yellow nodules that are uniform or slightly lobulated and often bulge from the cut surface. Tumor staging is via a TNM system (see testicular cancer staging).
Ultrasound is the first line imaging modality if a patient presents with a testicular abnormality. Features include:
- seminomas usually appear as a homogeneous intratesticular mass of low echogenicity compared to normal testicular tissue
- the mass is usually oval and well-defined in the absence of local invasion
- usually confined within the tunica albuginea, rarely extending to paratesticular structures
- internal blood flow is seen on color Dopper imaging
- cystic regions and calcifications are less common than in non-seminomatous germ cell tumors
- larger seminomas can have a heterogeneous appearance
Abdominal and pelvic CT are important in visualizing metastases both as a part of primary staging seminoma but also in primary diagnosis when a testicular mass is unknown.
Metastases to the para-aortic lymph nodes at the level of the renal vessels are the typical first site of spread owing to the lymphatic drainage of the testicles relating to embryological testicular descent. The nodal metastases are often bulky, of homogenous density and tend to encase surrounding vessels.
Inguinal or iliac lymph node metastases suggest lymphatic spread via the scrotum and therefore local tumor extension beyond the tunica vaginalis.
Visceral metastases are seen in ~5% of patients at presentation (lung, liver, bone, brain). Staging CT of the chest is only indicated when regional para-aortic lymph node spread is present or if there is an abnormal chest x-ray.
Following therapy, lymph node metastases reduce markedly in size but some inactive abnormal tissue persists which can be difficult to distinguish from residual disease and follow-up monitoring is required.
Usually appear as multinodular tumors of uniform signal intensity 3-4:
- T2: hypointense to normal testicular tissue
- T1+C (Gd): inhomogeneous enhancement
FDG-PET is less sensitive in initial staging than CT. Usually only used following treatment of seminoma to look for metabolic activity within residual lymphadenopathy or extranodal metastases.
Treatment and prognosis
Treatment involves surgical removal of the testicular primary (orchiectomy).
Radiotherapy to regional nodes if there is local disease (stage I) or limited nodal para-aortic metastases (non-bulky stage II) may be necessary (seminomas are radiosensitive, whereas non-seminomatous tumors are not).
Chemotherapy may be necessary if there is bulky para-aortic lymph node involvement of more distant disease. Four cycles of bleomycin, etoposide, and cisplatin (BEP) is currently standard of care.
Prognosis is good for all stages with greater than 90% cure rate. Survivors have an increased lifetime risk of developing other malignancies including testicular cancer in the remaining testicle, mesothelioma and cancer of the lung, colon, bladder, pancreas, and stomach.
The main differential for testicular mass in young adults is non-seminomatous germ cell tumor (NGCT) which usually appear more heterogeneous, often with cysts and calcification. Lymphadenopathy of NGCT may enhance more heterogeneously.
Testicular lymphoma is the main differential diagnosis to consider when para-aortic lymphadenopathy is the presenting finding or in the setting of bilateral testicular lesions.
- 1. Ulbright TM, Amin MB, Young RH. Tumors of the testis, adnexa, spermatic cord, and scrotum. Atlas of tumor pathology, fasc 25, ser 3. Washington, DC: Armed Forces Institute of Pathology, 1999; 1-290
- 2. Tan IB, Ang KK, Ching BC et-al. Testicular microlithiasis predicts concurrent testicular germ cell tumors and intratubular germ cell neoplasia of unclassified type in adults: a meta-analysis and systematic review. 2010;doi:10.1002/cncr.25231 - Pubmed citation
- 3. Woodward PJ, Sohaey R, O'donoghue MJ et-al. From the archives of the AFIP: tumors and tumorlike lesions of the testis: radiologic-pathologic correlation. Radiographics. 22 (1): 189-216. Radiographics (full text) - Pubmed citation
- 4. Tsili AC, Tsampoulas C, Giannakopoulos X et-al. MRI in the histologic characterization of testicular neoplasms. AJR Am J Roentgenol. 2007;189 (6): W331-7. doi:10.2214/AJR.07.2267 - Pubmed citation
- 5. Dogra VS, Gottlieb RH, Oka M et-al. Sonography of the scrotum. Radiology. 2003;227 (1): 18-36. Radiology (full text) - doi:10.1148/radiol.2271001744 - Pubmed citation
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