In this testicular teratoma, a dermoid structure lined by squamous cells with keratinous debris can be seen, surrounded by well-developed cartilage. Most ovarian teratomas are cystic, while most testicular ones are solid as seen here.
A closer view of the keratin flakes (bottom) and cartilage (top), separated by stroma.
Rhabdomyosarcoma is seen here, and it is arising in a teratoma.
The rhabdomyosarcomatous component is desmin positive.
As well as myogenin positive.
This teratoma developed bronchial epithelia and smooth muscle.
This is a different teratoma composed largely of mature cysts and brain tissue.
The components are entirely mature and intimately admixed.
The typical mesenchymal stroma is also present.
Teratomas (teras = monster in Latin) are "monstrous tumors", in which there are two or more components of germ cell layers (endoderm, mesoderm, ectoderm). Testicular teratomas may be mature in which the components are fully developed tissue or immature, in which there is a component of undifferentiated blastema-like cells.
While about 95% of ovarian germ cell tumors are pure teratoma, only about 4% of testicular germ cell tumors are seen in their pure form. Note that in the male, prepubertal teratomas are usually "pure" whereas postpuberal teratomas are usually admixed with another germ cell tumor- a component of "malignancy mixed germ cell tumor". Teratoma with embryonal carcinoma (the old rather outdated term is teratocarcinoma) is the most common combination, but teratomas can be found in conjunction with seminomas, choriocarcinomas, and yolk sac tumors as well.
Sometimes, elements of the teratoma may become malignant ("teratoma with malignant transformation"). For example, an enteric adenocarcinoma, squamous cell carcinoma, malignant glioma, rhabdomyosarcoma, or PNET, among others may evolve from the mature or immature elements.
Intratubular germ cell neoplasia may be found adjacent to the teratoma and IGCN is often considered a precursor to germ cell tumors.
The relative proportion of teratoma is quite different depending on the gender, with about 95% of ovarian germ cell tumors represented by pure teratoma, but only about 4% of testicular germ cell tumors
For postpubertal males, teratomas should be treated as a malignant tumor even if there are not immature or malignant elements. In up to 15% of teratomas (mature or immature), there is evidence of retroperitoneal lymph node metastases at the time of diagnosis.
Pure testicular teratoma in prepubertal boys have not been reported to metastasize, while testicular teratomas in adults are associated with clinical metastases in 60%.The finding of teratoma with somatic-type malignancy has been associated with a poor prognosis. Teratoma with malignant transformation is generally resistant to chemotherapy and requires complete surgical resection.