Germ cell tumours in children & teens — a clear explanation for worried parents

A germ cell tumour arises from primordial germ cells — the cells that are destined to become sperm or eggs in adult life. During foetal development, these cells travel from the yolk sac to the developing gonads (ovaries or testes). Occasionally, some of these cells stray off their intended path and settle in other parts of the body — the brain, the chest, the abdomen, or the tailbone — while the baby is still forming. If these misplaced germ cells begin to divide abnormally, a germ cell tumour develops. This is why germ cell tumours can occur in children and even newborns, long before puberty, and why they are not confined to the ovaries or testes. The tumour is not caused by anything the parents or child did. In most cases it arises from a developmental event that happened before birth, without any known hereditary cause.

A teratoma is the most common type of germ cell tumour in children and is a subtype within the broader germ cell tumour family. The word teratoma comes from the Greek for ‘monster tumour’ because, under the microscope, teratomas can contain a remarkable variety of tissues — including hair, teeth, cartilage, muscle, and even rudimentary structures — all arising from the germ cell’s potential to generate any tissue type in the body. Teratomas are classified as mature (containing fully developed, adult-type tissues; usually benign), immature (containing foetal-type tissues; may behave more aggressively), or malignant teratoma (when a component of the teratoma has become frankly cancerous). Not every teratoma is a cancer — many in young children are mature and benign — but all teratomas require careful pathological assessment because the presence of immature or malignant elements changes the management significantly.

In children and teenagers, germ cell tumours can appear in several locations depending on where the wandering germ cells settled during development. The most common locations include: the sacrococcygeal area (the tailbone region at the base of the spine) — this is the most frequent site in newborns and infants and is often detected at birth or on prenatal ultrasound; the ovaries in girls, especially around and after puberty; the testes in boys, where germ cell tumours are among the more common testicular masses in male children; the mediastinum (the chest cavity between the lungs); the abdomen and retroperitoneum (the space behind the abdominal organs); and the brain, particularly the pineal region and the suprasellar area (near the pituitary). The location of the tumour is one of the key factors the oncology team considers when planning investigations and treatment.

The signs of a germ cell tumour depend on where the tumour is growing and how large it has become. In newborns and infants, a sacrococcygeal teratoma may appear as a visible mass at the base of the spine or between the buttocks. In toddlers and young children, an abdominal mass, swelling in the lower abdomen, or difficulty passing urine or stools can sometimes be caused by a germ cell tumour pressing on nearby structures. In boys, a painless swelling or firm mass inside the scrotum should always be assessed, as it may indicate a testicular germ cell tumour. In girls approaching puberty, an ovarian germ cell tumour may cause lower abdominal pain, bloating, or a palpable abdominal mass; sudden severe abdominal pain can occur if the tumour causes the ovary to twist (ovarian torsion). Germ cell tumours in the brain can cause headaches, vision changes, or hormone disturbances such as early puberty (precocious puberty). None of these signs are specific to germ cell tumours — a proper medical evaluation is needed to determine the cause.

Diagnosing a germ cell tumour begins with a careful history and physical examination. Ultrasound is usually the first imaging investigation, as it can identify the size and character of a mass without radiation. Cross-sectional imaging with MRI or CT scan provides more detailed information about the tumour, its relationship to surrounding structures, and whether there is any spread to lymph nodes or distant sites. Blood tests for tumour markers — particularly alpha-fetoprotein (AFP) and beta-hCG (beta human chorionic gonadotropin) — are an important part of the diagnostic workup for germ cell tumours, because many (though not all) types produce these proteins in elevated quantities. It is important to note that AFP is normally elevated in infants under 12 months of age and only reaches adult reference ranges around the first birthday, so the team interprets AFP results in the context of the child’s age. A tissue biopsy or surgical removal of the tumour provides the definitive diagnosis — the pathologist examines the tissue under the microscope and classifies the exact tumour type.

Treatment depends on the type of germ cell tumour, its location, the child’s age, and whether it has spread. For mature teratomas that are entirely benign, surgical removal is often the complete treatment, and no further therapy is needed provided the tumour is fully removed and tumour markers are normal. For immature teratomas, the grade of immaturity and the child’s age influence whether surveillance alone or chemotherapy following surgery is recommended. For malignant non-teratomatous germ cell tumours (such as yolk sac tumours, germinomas, or embryonal carcinoma), the treatment programme typically involves surgery to remove or reduce the tumour combined with a course of chemotherapy. Germinomas — particularly those in the brain or gonads — are among the most treatment-responsive cancers in paediatric oncology and often respond well to chemotherapy and, where needed, radiation therapy. At CION, each child’s case is reviewed at a multidisciplinary tumour board — a team that includes medical, surgical, and radiation oncologists together — before any treatment is planned. We do not make rushed decisions.