drainage and ablation, with regard to the recurrence of the en- dometrioma (6). This study once again appears to highlight the need for a prospective study of ovarian endometriotic cysts, pre- ferably removed by oophorectomy, using a standardized method for examination, sampling, and histological evalua- tion, to elucidate better the pathogenesis of endometriomas and to determine an accurate frequency of the various cyst types. Camran Nezhat, M.D. Ceana Nezhat, M.D. Stanford University Medical Center Stanford, California Daniel Seidman, M.D. Tel Aviv University Tel Aviv, Israel Bulent Berker, M.D. Ankara University School of Medicine Ankara, Turkey Farr Nezhat, M.D. Mount Sinai School of Medicine New York, New York June 5, 2007 REFERENCES 1. Muzii L, Bianchi A, Bellati F, Cristi E, Pernice M, Zullo MA, et al. His- tologic analysis of endometriomas: what the surgeon needs to know. Fertil Steril 2007;87:362–6. 2. Nezhat C, Crowgey SR, Garrison C. Surgical treatment of endometriosis by laser laparoscopy. Fertil Steril 1986;45:778–83. 3. Sampson JA. Perforating hemorrhagic (chocolate) cysts of the ovary. Arch Surg 1921;3:245–323. 4. Nezhat F, Nezhat C, Allan CJ, Metzger DA, Sears DL. Clinical and histo- logical classification of endometriomas: implications for a mechanism of pathogenesis. J Reprod Med 1992;37:771–6. 5. Stratton P, Winkel CA, Sinaii N, Merino MJ, Zimmer C, Nieman LK. Lo- cation, color, size, depth, and volume may predict endometriosis in lesions resected at surgery. Fertil Steril 2002;78:743–9. 6. Hart RJ, Hickey M, Maouris P, Buckett W, Garry R. Excisional surgery versus ablative surgery for ovarian endometriomata. Cochrane Database Syst Rev 2005;3:CD004992. doi:10.1016/j.fertnstert.2007.07.1367 Reply of the Authors: First, we thank Nezhat et al. for their appreciation of our work (1) and for their valuable comments that have given us the opportunity to further clarify the findings of our study. Those authors report, as their first comment, that they do not agree with the conclusions of our study regarding the pathogenesis of endometriotic cysts. We want to stress the fact that we did not come to any conclusion on the pathogen- esis of endometriomas. Our study was merely a thorough histological evaluation of 70 endometrioma cyst walls that was performed by an unbi- ased pathologist who was not aware of the different theories on the pathogenesis of endometriomas. The data set provided by our study gives us a detailed description of the histological nature of the endometrioma wall that may help in the clinical decision of which treatment may be best for the endome- trioma. In our discussion section, we do make some clinical recommendations, as Nezhat et al. state in their letter, and we are happy that we and they, in this respect, follow exactly the same lines, by suggesting cystectomy as the technique of choice (1). This clinical recommendation, although it still is debated today, is supported by sound data from a meta-anal- ysis of randomized clinical trials (2). In our study, the histologic confirmation rate for endome- triosis was 100%. A mean of 60% (ranging from 10% to 98%) of the surface of the inner cyst wall was lined by en- dometrium. No other epithelial lining type was observed. In the areas of the inner wall that were not covered by endome- trium, only a fibrotic capsule could be observed. In 81% of the cases, beyond the fibrotic wall, ovarian tissue (stroma, follicles, or both) was observed. In no case was a transition noted from luteal tissue to the endometrial cyst. Only such a finding would give support to the existence of type II endometrioma, according to the classification by Nezhat et al (3). Admittedly, in their much larger series of 187 women, Nezhat et al. (3) also were not able to detect this finding. In a recent study by Scurry et al. (4), a thorough histolog- ical evaluation was performed in an attempt to classify endometriomas into different pathogenetic types. The con- firmation rate for endometriosis at histology was 100%. The investigators were able to identify only two types of cysts. The first, occurring in 10 (42%) of 24 evaluable spec- imens, was defined as ‘‘cortical invagination endome- trioma,’’ further defined as a cyst with a layer of ovarian cortex interspersed between the endometrial lining and the ovarian medulla. The second type, occurring in 14 (58%) of 24 evaluable specimens, was defined as ‘‘unclassified,’’ because it did not fall into any of the three preset categories. This second type of cyst was described as endometrial lin- ing surrounded by fibrosis, without identifiable ovarian tis- sue between the endometriosis and the medulla. Five specimens (17%) of the 29 that were included could not be assessed, other than the diagnosis of endometriosis, be- cause of extensive destruction of the tissue. In no case were a surface inclusion–related endometrioma (defined as a cyst with continuity between a surface-inclusion cyst and endometrial lining) or a physiological cyst–related en- dometrioma (defined as a cyst with continuity between a functional cyst and endometrial lining) observed. In sum- mary, Scurry et al. (4) were able to identify two types of en- dometriomas, one with only endometrial lining and fibrosis (58%) and one with endometrial lining, fibrosis, and ovarian tissue (42%). These figures are consistent with those re- ported in our study published elsewhere on the histology 1018 Letters to the Editor Vol. 88, No. 4, October 2007