title: A case of clear cell adenocarcinoma arising from endometriosis of the rectum treated by laparoscopic surgery.
abstract: BACKGROUND
  Malignant transformation of intestinal endometriosis occurring in the extraovarian sites is extremely rare. We report a very rare case of clear cell adenocarcinoma arising from endometriosis of the rectum.
  
  
  METHODS
  An 83-year-old woman was admitted with the complaint of hematochezia. Colonoscopy revealed a tumor around about half of the rectal circumference. Biopsy of the tumor revealed a well-differentiated adenocarcinoma. Low anterior resection was undergone laparoscopically under the diagnosis of rectal carcinoma. Histopathological examination revealed clear cell adenocarcinoma, invading the sub-serosa of the rectum, but no metastasis of the lymph nodes. Immunohistochemical staining showed strong positivity for cytokeratin 7, but no staining for cytokeratin 20 and CDX2. The tumor existed adjacent to the endometrial glands, which were stained positive for Estrogen receptor. Ultimately, the patient was diagnosed with clear cell adenocarcinoma arising from endometriosis. Eighteen months after surgery, there are no signs of tumor recurrence.
  
  
  CONCLUSIONS
  Clear cell adenocarcinoma arising from intestinal endometriosis has been reported in 7 cases, including our case. Careful observation is required because the prognosis of endometriosis after malignant transformation remains poor.
  
  
  CONCLUSIONS
  We report a very rare case of clear cell adenocarcinoma arising from endometriosis of the rectum treated by laparoscopic surgery.
authors.affiliation: Department of Coloproctological Surgery, Juntendo University, Faculty of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan. Electronic address: yokazawa@juntendo.ac.jp.
authors.forename: Yu
authors.initials: Y
authors.lastname: Okazawa
authors.affiliation: Department of Coloproctological Surgery, Juntendo University, Faculty of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan.
authors.forename: Rina
authors.initials: R
authors.lastname: Takahashi
authors.affiliation: Department of Coloproctological Surgery, Juntendo University, Faculty of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan.
authors.forename: Kosuke
authors.initials: K
authors.lastname: Mizukoshi
authors.affiliation: Department of Coloproctological Surgery, Juntendo University, Faculty of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Takehara
authors.affiliation: Department of Coloproctological Surgery, Juntendo University, Faculty of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan.
authors.forename: Shun
authors.initials: S
authors.lastname: Ishiyama
authors.affiliation: Department of Coloproctological Surgery, Juntendo University, Faculty of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan.
authors.forename: Kiichi
authors.initials: K
authors.lastname: Sugimoto
authors.affiliation: Department of Coloproctological Surgery, Juntendo University, Faculty of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Takahashi
authors.affiliation: Department of Coloproctological Surgery, Juntendo University, Faculty of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Kojima
authors.affiliation: Department of Coloproctological Surgery, Juntendo University, Faculty of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan.
authors.forename: Michitoshi
authors.initials: M
authors.lastname: Goto
authors.affiliation: Department of Coloproctological Surgery, Juntendo University, Faculty of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Okuzawa
authors.affiliation: Department of Coloproctological Surgery, Juntendo University, Faculty of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Tomiki
authors.affiliation: Department of Human Pathology, Juntendo University, Faculty of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Yao
authors.affiliation: Department of Coloproctological Surgery, Juntendo University, Faculty of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Sakamoto
keywords: Clear cell adenocarcinoma; Endometriosis; Rectal tumor