Analysis of positron emission tomography/computed tomography in patients to differentiate between malignant transformation of endometrioma and endometrioma

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. 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. 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 %). PET/CT is a good diagnostic tool for MTOE using the optimal SUVmax cut-off of 4.0 (75 % sensitivity and 100 % specificity).