Endometrioid carcinoma of the ovary

Endometrioid carcinomas of the ovary are a a sub-type of an epithelial ovarian tumour tumoursof epithelial origin. The vast majority are malignant and invasive. On imaging, they are usually characterised as complex nonspecific solid-cystic masses and found associated with endometriosis. 

Epidemiology

Endometrioid carcinomas account for 8-15% of all ovarian carcinomas. It is considered the second commonest malignant ovarian neoplasm ⁸.

Both endometrioid and clear cell tumours are frequently associated with endometriosis ⁹. 

Pathology

The typical gross appearance of these tumours is similar to that of other epithelial lesions, with variable cystic and solid components. Occasionally, it may be completely solid.

Histologically, an endometrioid carcinoma is characterised by the appearance of tubular glands, and bears a strong resemblance to the endometrium. Gross morphological appearance is that of a mass with both solid and cystic areas ².  Squamous differentiation can be present in more than a third of patients ⁸.

A benign endometrioid carcinoma is relatively uncommon and when it is benign it tends to be an ovarian cystadenofibroma ³.

Associations

• synchronous endometrial carcinomaor or endometrial hyperplasia may be present in up to a third of cases
  • the endometrial abnormality is thought to represent an independent, primary lesion rather than metastatic disease
• endometrioid carcinoma is the most common malignant neoplasm arising within an endometrioma, although overall this is an uncommon occurrence

Location - laterality

Bilateral involvement can be seen in 25-40% of cases ^1-2,8.

Radiographic features

Imaging findings are often non-specific and include a large, complex cystic mass with solid components.

There may be associated endometrial thickening, evidence of endometriosis or a contralateral mass.

Pelvic MRI

Reported signal characteristics include:

• T2:
  • relatively low signal intensity of the tumour wall
  • shading sign may be seen ³
• T1 C + (Gd): can show mild enhancement ³

Treatment and prognosis

An endometriodendometrioid histology may carry a slightly better prognosis than a serous or mucinous cystadenocarcinoma of the ovary (not a serous tumour in general) independent of stage ^5,8. Pure endometrioid tumours carry a far better outcome than a mixed variety.

Differential diagnosis

Metastases to the ovary with colon cancer could be considered especially if the ovarian lesion is bilateral or if there is a known colonic mass, especially due to strong histological similarity. Differentiation from metastatic endometrial cancer can also sometimes can be difficult.

See also

• ovarian tumours