Endometrioid carcinomas of the ovary are a sub-type of epithelial ovarian tumours. The vast majority are malignant and invasive. On imaging, they are usually characterised as complex nonspecific solid-cystic masses and found associated with endometriosis.
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.
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.
- synchronous endometrial carcinoma 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.
Imaging ﬁndings are often non-speciﬁc and include a large, complex cystic mass with solid components.
Reported signal characteristics include:
- 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 endometrioid 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.
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 be difficult.
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- 9. Foti PV, Attinà G, Spadola S, Caltabiano R, Farina R, Palmucci S, Zarbo G, Zarbo R, D'Arrigo M, Milone P, Ettorre GC. MR imaging of ovarian masses: classification and differential diagnosis. Insights into imaging. 7 (1): 21-41. doi:10.1007/s13244-015-0455-4 - Pubmed