Ovarian yolk sac tumours are malignant germ cell neoplasms most common in young females, with characteristic Schiller-Duval bodies on histopathology, elevated AFP levels, and a typically heterogeneous appearance with areas of haemorrhage and necrosis on imaging.
Description
Ovarian yolk sac tumours (YSTs), also known as endodermal sinus tumours, are malignant neoplasms arising from germ cells. They are the second most common type of ovarian germ cell tumour. While they can occur in all age groups, they are most frequently seen in children and young women under the age of 20.
Pathogenesis
YSTs originate from primordial germ cells, which normally give rise to eggs in the ovaries. These cells undergo abnormal differentiation, leading to the formation of tumour cells resembling the yolk sac, allantois, and other extraembryonic tissues.
Subtypes
There are no recognised subtypes of ovarian YSTs. They are a distinct type of germ cell tumour.
Epidemiology, Risk Factors & Associations
- Represent approximately 20% of all ovarian germ cell tumours.
- Most common in children and young women, typically below the age of 20.
- No specific risk factors identified.
Clinical Features
- Most commonly presents with abdominal pain and distension.
- May present with precocious puberty in prepubescent girls due to increased secretion of human chorionic gonadotropin (hCG).
Complications
- Metastatic spread to the omentum, lymph nodes, liver, lungs, and brain.
- Acute complications such as rupture and haemorrhage.
Pathological Features
Histopathology
- Macroscopic: Large, unilateral, solid or mixed solid-cystic mass. Necrosis, haemorrhage, and cystic degeneration are common.
- Microscopic: Characterised by the presence of Schiller-Duval bodies, which resemble a central vessel surrounded by germ cells within a space that appears similar to a glomerulus.
Serology
- Elevated alpha-fetoprotein (AFP) levels, which can be used to monitor treatment response and detect recurrence.
Biochemistry
- No specific findings.
Radiological Features
General Features
- Large, complex, solid-cystic ovarian mass.
- Can show necrosis, haemorrhage, and septations.
- Calcifications are seen in about 20% of cases.
CT
- Non-contrast: Heterogeneous mass with areas of low attenuation corresponding to necrosis or cystic change.
- Contrast-enhanced: Enhancing solid components and septations.
MRI
- T1WI: Heterogeneous signal intensity due to haemorrhagic, necrotic, and cystic components.
- T2WI: Heterogeneous signal intensity due to solid and cystic components.
- T1 C+: Enhancing solid components and septations.
- DWI/ADC: Restricted diffusion in solid components, indicating malignancy.
PET FDG
- Not typically used in the assessment of YSTs.
Grading and Staging
Grading of YSTs is not typically performed. Staging is based on the FIGO staging system for ovarian tumours.
Diagnosis
Diagnosis requires histopathological examination of the tumour, demonstrating typical microscopic features, along with markedly elevated serum AFP levels.
Differential Diagnosis
- Mature cystic teratoma: More common in the same age group, typically shows fat and calcifications (tooth, bone).
- Granulosa cell tumours: Occurs in a wider age range, characterised by inhibin B and estradiol production, leading to endometrial thickening.
Management
Managed by gynaecologic oncologists. Treatment involves surgical resection, followed by chemotherapy for any residual disease or metastatic spread.