Purpose: Of those patients who undergo open surgery for a suspicion of malignant transformation of endometrioma (MTOE) due to solid nodule enhancement identified by contrast-enhanced magnetic resonance imaging (MRI), some benign endometrioma cases are included. The aim of this retrospective study was to determine the value and diagnostic accuracy of positron emission tomography/computed tomography (PET/CT) using 18-fluoro-2-deoxy-D-glucose (FDG) to differentiate between MTOE and endometrioma.
Patients and methods: We retrospectively analyzed 1599 consecutive patients who underwent laparoscopic surgery for the diagnosis of endometrioma preoperatively and 31 patients who underwent open surgery for a suspicion of MTOE preoperatively from January 2003 to December 2011. We analyzed the age, serum CA125 levels, and MRI findings of the patients and calculated the optimal cut-off value for PET/CT using receiver operating characteristic curve analysis.
Results: Of the 1,599 patients who underwent laparoscopic surgery for a suspicion of endometrioma preoperatively, malignancy was identified in one (0.062 %) patient. Of the 31 patients who underwent open surgery for a suspicion of MTOE preoperatively, 11 were diagnosed with endometrioma (false positive group) and 20 with MTOE stage I (positive group). Age, tumor size, presence of shading on MRI and maximum standardized uptake values (SUVmax) on PET/CT were significantly different between the two groups. A SUVmax cut-off >4.0 is capable of excluding endometrioma cases, with 75 % sensitivity and 100 % specificity (area under the curve 90 %).
Conclusion: PET/CT is a good diagnostic tool for MTOE using the optimal SUVmax cut-off of 4.0 (75 % sensitivity and 100 % specificity).
Keywords: Endometrioma; MRI; Malignant transformation; PET/CT.