Embryonal carcinoma (ECA) is a highly malignant tumor composed of tumor cells with ovoid to columnar profiles, clear to granular or amphophilic cytoplasm, and markedly pleomorphic nuclei resembling primitive cells that retain the ability to differentiate toward somatic or extraembryonic structures.
The pure form of embryonal carcinoma accounts for only 2–10% of GCTs, but ECA is very frequent (87%) in mixed neoplasms, being after seminoma the most prevalent testicular GCT.
It occurs a decade before seminoma and the mean patient age at diagnosis is 25–32 years. ECA is rare in childhood apart from a disorder of sex development and after age 50.
Most patients present with a testicular mass; almost 10% of patients have metastases as presenting symptoms, occurring in the retroperitoneal lymphnodes.
Different protocols are applied and chemotherapy alone or in association with lymphadenectomy is performed after orchiectomy in metastatic setting (Albers et al. 2015).
Pure ECA behaves more aggressively than mixed GCTs; nevertheless, it can be cured with modern therapy protocols. In mixed GCTs, the metastases are directly proportional to the percentage of ECA in mixed GCTs (Rodriguez et al. 1986). Twenty percent have supradiaphragmatic lymph node and/or visceral metastases, and hematogeneous spread to the lungs or other sites may occur.
ECA is mostly smaller and not as well circumscribed as seminomas. The cut surface is soft, grayish, and focally hemorrhagic or necrotic.
The tumoral cells in ECA show strong positive reaction to cytokeratins, CD 30, SOX2, and OCT 3/4, and are negative for CD 117, SOX17 with only focal positivity for PLAP, AFP, and beta HCG in syncytiotrophoblastic giant cells. CD 30 immunoreactivity may be lost after chemotherapy (Berney et al. 2000), while in multiple-relapse/chemoresistant cases the persistence of CD 30 expression is associated with a significantly poorer prognosis and it is an independent prognostic factor for survival (Giannatempo et al. 2013).
ECAs are triploid or hypotriploid tumors. Cytogenetic analysis shows unspecific anomalies, but i(12p) and increased copy numbers of 12p are present in most cases. There is a correlation between the aggressiveness of the tumor and the number of isochromosome copies.
Many other germ cell tumor histotypes may be confused and for this reason we address to the specific entities for a detailed description. Any confusion with seminoma for the therapeutic consequences is strongly discouraged: in such cases, the use of immunohistochemical markers (CD 30 and SOX2 positivity in ECA, CD 117, and SOX 17 in seminoma) is recommended. ECA may be confounded with large B cell-lymphoma, especially if it is CD 30 positive.
References and Further Reading
- Giannatempo, P., Paolini, B., Miceli, R., Raggi, D., Nicolai, N., Farè, E., Catanzaro, M., Biasoni, D., Torelli, T., Stagni, S., Piva, L., Mariani, L., Salvioni, R., Colecchia, M., Gianni, A. M., & Necchi, A. (2013). Persistent CD30 expression by embryonal carcinoma in the treatment time course: Prognostic significance of a worthwhile target for personalized treatment. Journal of Urology, 190(5), 1919–1924.CrossRefGoogle Scholar