Joao Lopes Dias MEd, Presenter: Nothing to Disclose

Filipe Veloso Gomes MBChB, Abstract Co-Author: Nothing to Disclose

Rita Nobre Lucas MD, Abstract Co-Author: Nothing to Disclose

Teresa Margarida Cunha MD, Abstract Co-Author: Nothing to Disclose

To investigate if the shading sign is exclusive of endometriomas and to analyze its different patterns.

346 women with adnexal masses who underwent 1,5-T or 3-T MRI were included in this retrospective, descriptive, board-approved study. The shading sign was found in 56 patients, but 5 cases were excluded due to lack of follow-up or histological correlation. 51 women (mean age, 47 years) were finally considered. The type of tumor was recorded taking into account clinical and imaging follow-up, imaging-guided biopsies and surgical specimens analysis. The pattern of shading was also described for each case.

30 endometriomas (58,8%), 6 serous adenocarcinomas, 5 endometrioid adenocarcinomas, 3 mucinous borderline tumors, 3 cystic mature teratomas, 1 unclassifiable primary adenocarcinoma, 1 mucinous unclassifiable primary tumor, 1 mucinous tumor within an endometrioid cyst, and 1 struma ovarii were found among the 51 cases with positive shading. The overall sensitivity and specificity of shading in the diagnosis of endometrioma was 73% and 93%, respectively. Positive and negative predictive values were 59% and 96%, respectively. Five shading patterns were identified: layering (8, 15,7%), liquid-liquid level (6, 11,8%), homogenous (23, 45,1%), heterogeneous (6, 11,8%), and focal/multifocal shading within a complex mass (10, 19,6%). No significant correlation was found between these patterns and the type of tumor. However, the authors emphasize two points: firstly, homogenous shading was the most prevalent pattern in endometriomas (17 in 30); secondly, half of the cases with focal/multifocal shading within a complex mass corresponded to endometrioid adenocarcinomas (5 in 10).

Despite the moderate-to-high levels of sensitivity and specificity, the shading sign is not exclusive of endometriomas or endometrioid tumors, and may be found in several benign and malignant non-endometrioid adnexal tumors.

The shading sign is a distinguished feature of endometriomas at magnetic resonance imaging (MRI). It corresponds to the complete or partial loss of signal intensity of an hyperintense adnexal cyst from T1-weighted images (T1WI) to T2-weighted images (T2WI). However, in daily practice, some non-endometrioid tumours of distinct histological types also show this sign and it should not lead to erroneous diagnosis.

Lopes Dias, J, Veloso Gomes, F, Lucas, R, Cunha, T, The Shading Sign: Is It Exclusive of Endometriomas?.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14015455.html