Paediatrics: Germ cell tumours

Germ cell tumours

Germ cell tumours (GCTs) comprise a heterogeneous group of neo-plasms, often with mixed histology. They arise from primordial germ cells in gonads or, following aberrant germ cell migration, in midline extrago-nadal sites, including sacrococcygeal, mediastinal, or CNS sites. GCTs are rare occurring in 3–5 per million children <15yrs of age, with peak inci-dence seen in children aged <3yrs. 10% of girls with ovarian GCTs are found to have an underlying intersex state.

The nomenclature of GCTs is complicated.

·Mature teratoma is benign.

·Immature teratoma may disseminate locally.

·Malignant GCTs:

·  germinoma (or seminoma, dysgerminoma, depending on site) is totipotent;

·  teratoma, yolk sac tumour (YST), choriocarcinoma (CHC), and embryonal carcinoma (EC) represent more differentiated forms.

·Secreting tumours (YST, CHC, some immature teratomas, and mixed tumours) characterized by secretion of AFP and/or hCG, which may be used for diagnosis, monitoring of treatment response, and detection of recurrence.

Presenting symptoms

Site-dependent. Testicular masses are usually painless. Ovarian tumours present as either painful or painless abdominal mass. Metastases are rarely present at diagnosis (lungs, the commonest site, bone, and bone mar-row).

Diagnosis and staging

·Measurement of AFP and B-hCG in serum (and CSF for CNS disease).

·Imaging of primary: US, CT, or MRI.

·Biopsy of unresectable tumours (unless unsafe) and/or imaging and markers sufficient to make diagnosis.

·CT scan of chest and abdomen.

·Bone marrow and isotope bone scan to look for metastases.

Treatment of extracranial tumours

·Surgery followed by observation for low risk tumours (e.g. mature/ immature teratoma and gonadal stage I).

Note: Testicular tumours should be removed via an inguinal approach. Sacrococcygeal teratomas should be removed together with the coccyx to reduce risk of malignant relapse. Chemotherapy is reserved for intermedi-ate and high risk disease.

Prognosis 

Survival >90% for malignant extracranial GCTs.