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Atypical endometriosis: a clinicopathologic study of 163 cases



To investigate the clinicopathologic features of atypical endometriosis (AEM), and to discuss the relations between AEMs and tumors.


A retrospective analysis was performed on 163 cases of AEMs. The changes in the glandular epithelium, stroma, and their background and the relationship with coexisting tumors were observed.


The AEMs account of for 4.4% (163/3,724) of the endometriosis (EM) cases. Of 172 AEM foci of 163 patients, 168 were in the ovary, and the other 4 were in the fallopian tube, cervix and uterine serosa. Of the cases of ovarian EM, 6.8% were AEM. All of the 27 cases (15.7%) of the AEMs associated with a tumor were found in the ovaries, of which 15 were malignant, 9 borderline, and 3 benign. Of the ovary AEMs, 14.9% were associated with a borderline or malignant tumor. The AEM epithelia were mainly arranged in the form of surface epithelia, with only a few glands. Present were characteristic features of moderate to marked pleomorphism, epithelial tufting, bud or firework-like structures on microscopy. Epithelial metaplastic changes were observed in 86 cases (50%) of the 172 AEM foci. Epithelium, endometrioid stroma, and fibrotic-collagen formed a three-layer structure in the wall of the AEM cysts. The endometrioid stroma were usually thin compared to the fibro-collagen tissue. The transformation from an AEM to a tumor was found in most of the malignant tumors.


AEM lesions have some features which are similar and also differ from both of the tumor and EM. AEMs have a relative higher potential for tumorigenesis and canceration, especially for ovarian cancer. The process of damage, repair, and scarring in EM foci over a long period may play a role in the development of EM into AEM and eventally into tumor formation.

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Correspondence to Donghui Guo.

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Guo, D., Pang, S. & Shen, Y. Atypical endometriosis: a clinicopathologic study of 163 cases. Chin. J. Clin. Oncol. 4, 405–410 (2007).

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  • atypical endometriosis
  • ovarian tumor
  • clinicopathology