Difference Between Teratoma and Seminoma

Both teratoma and seminoma are germ cell tumors, which share some of the similar characteristics, but they do differ in many ways. Teratoma is a well-encapsulated tumor having components derived from all three germ layers, but seminoma arises from the germ cell epithelium of the seminiferous tubules. This article points out the differences between these two terms.

Teratoma

As mentioned above, it is a well encapsulated tumor having components derived from all three germ cell layers. It is classified as mature and immature types where the latter is malignant. All teratomas in adults are biologically malignant, in contrast to children under 12 yrs where they behave as benign neoplasm.

Since it is considered as a congenital tumor, it presents at birth. But sometimes the tumors are not detected until adulthood. Alpha feto protein may be largely elevated.

Microscopically, teratoma shows somatic differentiation and contain elements of all three germ layers; endoderm, mesoderm and ectoderm. It may comprise brain, respiratory and intestinal mucosa, cartilage, bone, skin, teeth or hair.

In the fetus, they are not dangerous but rarely can cause mass effect and vascular stealing which can lead to heart failure in the fetus.

Management includes complete surgical excision of the tumor. For malignant teratomas, chemotherapy is given after the surgery.

Seminoma

It is the most treatable and curable cancer in the testis. It usually originates from the germinal epithelium of the seminiferous tubules. 50% of the germ cell tumors in the testis are seminoma. If it occurs in the ovary, it is called dysgerminoma while, in the central nervous system, it is called a germinoma.

Clinically the patient presents with a testicular mass, testicular atrophy, testicular pain and back pain following metastasis to the vertebra.

Investigation findings include high level of alkaline phosphatase, elevated human chorionic gonadotropin. In classic seminoma, serum alpha feto protein is not elevated.

Macroscopically, it appears as fleshy and lobulated mass. The tumor is bulging from the cut surface and hemorrhagic areas may be seen.

Microscopically, classic seminoma is characterized by nests of uniform large-round cells that have distinct cell membrane, central nuclei, prominent nucleoli, and clear cytoplasm containing abundant glycogen, which resemble the primary spermatocytes in the seminiferous tubule.

Other varieties include spermatic seminoma characterized by maturation of the tumor cells, which resemble secondary spermatocytes. Anaplastic seminoma is more pleomorphic and has a higher rate of mitotic figures.

Management includes inguinal orchidectomy in almost all cases. The tumor also shows a dramatic sensitivity to radiotherapy and chemotherapy with a good survival rate of >90% in early stages.