Ovarian dysgerminoma, a malignant germ cell tumour, is the most common ovarian neoplasm in children and young women, often presenting with elevated LDH and a large unilateral, solid ovarian mass.
Description
Ovarian dysgerminoma is the most common germ cell tumour of the ovary and is equivalent to the testicular seminoma in males and intracranial germinoma. It typically presents as a unilateral, solid mass in young women, with a significant proportion diagnosed in childhood. These tumours are malignant but generally have a good prognosis due to their sensitivity to radiotherapy and chemotherapy.
Pathogenesis
Dysgerminomas arise from primitive germ cells in the ovary. They are characterised by a lack of differentiation, and thus, they closely resemble primordial germ cells in an early stage of development.
Subtypes
There are no recognised subtypes of ovarian dysgerminoma.
Epidemiology, Risk Factors & Associations
- Most common in young women and children
- Associated with gonadal dysgenesis and Turner syndrome
Clinical Features
Patients may present with abdominal pain or an abdominal mass. Some patients may have symptoms related to the production of beta-human chorionic gonadotropin (β-HCG) such as amenorrhoea or gynaecomastia.
Complications
Metastases, if they occur, are typically to the contralateral ovary, peritoneum, and lymph nodes.
Pathological Features
Histopathology
- Macroscopic: Large, lobulated, and solid tumour with a smooth surface, often with areas of necrosis or haemorrhage.
- Microscopic: Composed of large, uniform cells with clear or lightly staining cytoplasm and centrally located nuclei
Serology
- Elevation of serum lactate dehydrogenase (LDH) and, less commonly, β-HCG
Immunohistochemistry
- Positive for OCT4 (nuclear positivity) and CD117 (membranous positivity)
Radiological Features
General Features
- Often presents as a large, solid, and well-circumscribed unilateral ovarian mass
- May have cystic degeneration or necrosis
- May present with metastatic disease to the peritoneum
- Calcification is rare
US
- B-mode: Often appears as a large, well-circumscribed, predominantly solid mass with internal echoes
- Doppler: May show moderate to high vascularity
CT
- Non-contrast: Homogeneous attenuation, cystic degeneration or necrosis may be present
- Contrast-enhanced: Moderate enhancement in the arterial phase, persistent enhancement in the venous phase
MRI
- T1WI: Isointense to slightly hypointense compared to muscle
- T2WI: Hyperintense with areas of low signal intensity if haemorrhage is present
- T1 C+ (Gd): Moderate, homogenous enhancement
- DWI/ADC: Restriction of diffusion due to high cellularity
PET FDG
- May show intense uptake due to high metabolic activity of the tumour
Grading and Staging
The FIGO (International Federation of Gynaecology and Obstetrics) system is used to stage ovarian cancers, including dysgerminomas.
Diagnosis
Imaging can suggest the diagnosis, especially in the appropriate clinical context, but definitive diagnosis requires histological confirmation, often with serum LDH and β-HCG correlation.
Differential Diagnosis
- Endometrioid carcinoma of the ovary: Characteristically presents in older women with endometriosis. Tumours often bilateral and can show irregular solid and cystic components with enhancement. Calcifications are rare.
- Granulosa cell tumour: Occurs in a slightly older age group. Characteristically demonstrates haemorrhagic cysts and can secrete oestrogen leading to endometrial thickening.
- Mature cystic teratoma (a.k.a. dermoid cyst): Generally occurs in younger women and demonstrates fat and calcifications (Rokitansky nodule).
- Ovarian fibroma: Characterised by very low signal on T2 and often associated with Meigs syndrome.
- Metastases: Often bilateral with a solid or complex appearance. History of a primary malignancy is usually present.
Management
Treatment typically involves surgical resection followed by chemotherapy or radiotherapy, depending on the stage of the disease.