Using near-infrared imaging to discriminate malignant from benign endometriosis

Using near-infrared imaging to discriminate malignant from benign endometriosis

Near-infrared light as a potential tool for identifying malignant transformation of endometriosis

Key Points


  • This is a single-center retrospective study to investigate the use of the near‑infrared approach to discriminate malignant transformation from ovarian endometrioma.


  • Tools that can provide quantitative discrimination between endometriosis‑associated ovarian cancer and benign ovarian endometrioma may have significant clinical application to reduce the cancer-related burden associated with endometriosis.

What's done here:

  • Cystic fluid samples were collected from ovarian endometrioma (34 patients) and endometriosis‑associated ovarian cancer (12 patients).
  • The light reflected the individual sample (also known as change in luminance) was recorded spectrally by a near‑infrared CCD camera with a band‑path filter at 800 nm.


  • The change in luminescence in endometriosis‑associated ovarian cancer was significantly lower compared to ovarian endometrioma.
  • The change in luminescence positive correlated with hemoglobin levels in the cystic fluid.
  • The diagnostic sensitivity and specificity were 83.3 and 94.1% 


  • Other factors such as heme iron and free iron may have affected data acquired at 800 nm wavelength.
  • This is a small scale evaluation.
  • Due to the complex anatomy of reproductive organs, their non‑invasive imaging requires a near‑infrared CCD camera with strong sensitivity and high spatial resolution, which still require much development for clinical usefulness.

Lay Summary

Endometriosis usually begins as a benign disorder with an increased risk of developing ovarian and endometrial cancers. Endometrioid and clear cell carcinoma histologic subtype of ovarian cancer partially originate from endometriosis.

Recent studies on the pathogenesis of endometriosis‑associated ovarian cancer suggest that hemoglobin (Hb), heme and iron‑induced oxidative stress in ovarian endometrioma cystic fluid may be responsible for the malignant transformation of endometriosis. The overproduction of iron‑induced oxidative stress could trigger carcinogenesis by damaging DNA. Hence, cystic fluid Hb species may be useful biomarkers to diagnose between endometriosis-associated ovarian cancer and ovarian endometrioma differentially.

Advances in optical technology allow development of quantitative medical tools. When near‑infrared light is used to analyze cystic fluid, the influence of photon attenuation and scattering varies depending on Hb concentration in the content. Also, light in the near‑infrared spectrum can penetrate tissues including bone and muscle efficiently.

The research article by Kawahara et al. aims to use near-infrared light to discriminate endometriosis‑associated ovarian cancer and ovarian endometrioma. The authors hypothesized that changes in luminance across cystic fluid measured using a near‑infrared sensor camera could determine the Hb concentration of the cystic fluid. Thus, this approach can be developed into an ex vivo assay to differentiate malignant transformation of endometriosis.

Cystic fluid samples were collected from 34 patients with ovarian endometrioma and 12 patients with endometriosis‑associated ovarian cancer. The light reflected from each sample of cystic fluid, i.e., the change in luminance from these samples were spectrally measured by a near‑infrared CCD camera with band‑path filter (800 nm). The difference in luminance of cystic fluid from the endometriosis-associated ovarian cancer group was significantly lower compared with that of the ovarian endometrioma group. Hence this approach could serve as a simple method to detect endometriosis-associated ovarian cancer from the benign ovarian endometrioma. The assay sensitivity and specificity were reported to be 83.3% and 94.1%, respectively. 

In summary, the luminance value obtained from ex vivo cystic fluid samples at an 800‑nm wavelength may be a useful tool to discriminate malignant transformation from benign ovarian endometrioma. Although the future development of this technology for non‑invasive imaging in deep tissue still requires a near‑infrared CCD camera with strong sensitivity and spatial resolution, this study provides a new approach for the basis of developing a future tool to discriminate malignant and benign endometriosis.

Research Source:

malignancy imaging


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