Yolk Sac Tumor, from the CureRays guide library.

Yolk sac tumor is a fast-growing germ-cell cancer of the ovary or testicle (and sometimes other sites) that mostly affects children and young adults — it reliably raises the blood marker AFP, and modern surgery plus chemotherapy cure the large majority of patients.

What it is.

Yolk sac tumor — also called endodermal sinus tumor — is a malignant germ-cell cancer that grows from the body's primitive egg- and sperm-forming cells. It most often arises in the ovary or testicle, but because germ cells travel along the midline early in development, it can also appear in places like the tailbone area (sacrococcygeal), the chest (mediastinum), or the brain. It is most common in infants, children, and young adults. Its signature feature is that it produces a protein called alpha-fetoprotein (AFP) that can be measured in the blood, giving doctors a reliable way to diagnose it, track how well treatment is working, and detect recurrence. Yolk sac tumors tend to grow quickly, but they are very responsive to chemotherapy, so even advanced disease is usually curable. Yolk sac tumor cells are also often part of 'mixed' germ-cell tumors that contain several germ-cell types together.

How radiation treats it.

Radiation damages the DNA inside cancer cells so they can no longer divide and survive, while normal cells are better at repairing themselves. For yolk sac tumors, chemotherapy and surgery do nearly all the work, and radiation is rarely needed — which is good news, because most patients are children and young adults whose growing tissues are best protected from radiation. When radiation is used for an unusual resistant spot, it is given as short, painless sessions and leaves no radioactivity in your body, so you remain safe to be around family and children.

The ways we can treat it.

Surgery. The primary local treatment — removes the bulk of the tumor, establishes the diagnosis, and, for early disease, can be curative on its own.

Radiation (rarely used). Radiation has little routine role in yolk sac tumor because chemotherapy works so well and patients are usually very young, when avoiding radiation protects growing tissues. It is reserved for unusual, treatment-resistant situations.

Palliative radiation. In the uncommon resistant or recurrent case, a short course of targeted radiation can relieve pain or other symptoms from a specific spot.

Questions we hear often.

What does the AFP blood test mean for me? Yolk sac tumors make a protein called AFP that shows up in the blood. Your team uses it to confirm the diagnosis, to check that treatment is shrinking the tumor (the level should fall), and to watch for any return of the cancer afterward.

Is this cancer curable? Yes — yolk sac tumor is highly curable. Even when it has spread, the combination of surgery and platinum-based chemotherapy cures the large majority of patients, including most children and young adults.

Will treatment affect fertility? Surgery is often fertility-sparing, removing only the affected ovary and tube or the affected testicle. Chemotherapy can affect fertility, so your team may discuss options such as sperm or egg preservation before treatment begins.

This guide is informational only. It is not medical advice — please confirm anything here with your care team.