The evaluation of small tissue structures called mural nodules via magnetic resonance imaging can help with the accuracy of a diagnosis by distinguishing between ovarian endometriosis lesions and endometriosis-associated ovarian cancer, according to a report in the journal Magnetic Resonance in Medical Sciences.

Transvaginal ultrasonography, also known as endovaginal ultrasound, is an imaging technique that allows internal visualization of the reproductive female organs, providing useful diagnostic information. In clinical practice, it is commonly used as the first method to detect abnormal tissue growth in structures surrounding the uterus, such as ovarian endometriosis.

Ultrasonography can easily detect ovarian endometriosis lesions due to their characteristic fluid structure. However, sometimes these cysts can have internal blood clots or more solid components, such as mural nodules or small tissue projections, which with sonographic imaging can appear similar to structures found in malignant growths.

Correct identification of the nature of ovarian lesions is critical for prompt and adequate patient care. Clinicians often use pelvic magnetic resonance imaging (MRI) to solve these diagnostic conundrums and to confirm endometriosis-associated ovarian cancer.

In the study titled, “Factors that Differentiate between Endometriosis-associated Ovarian Cancer and Benign Ovarian Endometriosis with Mural Nodules,” researchers at the Nara Medical University, in Japan, compared the results of pelvic MRI evaluations of 42 cases of benign ovarian endometriosis with the imaging data of 40 cases of malignant transformation lesions.

The research team found that 78.6% of the samples collected of ovarian endometriosis presented mural nodular lesions, which were actually due to retracted blood clots. When evaluated by MRI, ovarian endometriosis cysts had a smaller size and presented smaller mural nodules compared to endometriosis-associated ovarian cancer lesions.

The mural nodules found in malignant cases were more likely to be taller than wider, “suggesting that this shape is specific for differentiating malignant from benign nodules,” the researchers wrote. Overall, these findings can help in decision-making during the diagnosis of malignant transformation in endometriosis-associated ovarian cancer.

“These potential [MRI] features may help clinicians in the diagnosis,” researchers wrote. “Further clinical study will evaluate the reliability and validity of ultrasound imaging on the shape and location of mural nodules with their corresponding MRI measurements.”