title: Intramural metastasis of T1 rectal cancer: report of a case report.
abstract: BACKGROUND
  Intramural metastasis (IM) is extremely rare in colorectal cancer, although it often occurred in esophageal cancer.
  
  
  METHODS
  We report a rare case of T1 rectal cancer with IM which was successfully resected by laparoscopic surgery. A 62-year-old man was admitted to our institution for the treatment of rectal cancer detected by medical examination. Colonoscopy revealed two tumors in the rectum: a type II rectal cancer of 2 cm in diameter located 5 cm proximal to the anal verge and a submucosal tumor of 1 cm in diameter located approximately 1.5 cm proximal to the rectal cancer. Abdominal computed tomography (CT), magnetic resonance imaging (MRI), and transrectal ultrasonography indicated the rectal cancer invaded into the submucosal layer with no metastasis to regional lymph nodes or distant organs. The patient underwent laparoscopic intersphincteric resection.Histopathological analysis revealed that the rectal cancer was moderately differentiated adenocarcinoma (stage I; pT1N0M0 according to the 7th edition of UICC) with severe lymphovascular invasion (ly1, v3) and that the submucosal tumor was composed of moderately differentiated adenocarcinoma proliferating within the muscularis propria. A number of features of the submucosal tumor indicated that this was an IM of the rectal cancer: clearly distinct location from the rectal cancer, growth predominantly within the muscularis propria, similar structural and cellular heterogeneity, and the presence of tumor emboli within vascular vessels. The patient was postoperatively followed for more than 4 years without any sign of recurrence.
  
  
  CONCLUSIONS
  To the best of our knowledge, this is the first report of the T1 rectal cancer with IM.
authors.affiliation: Department of Surgery, Graduate School of Medicine, Kyoto University, 54 Shogoin- Kawara-cho, Sakyo-ku, 606-8507, Kyoto, Japan.
authors.forename: Kosuke
authors.initials: K
authors.lastname: Toda
authors.affiliation: Department of Surgery, Graduate School of Medicine, Kyoto University, 54 Shogoin- Kawara-cho, Sakyo-ku, 606-8507, Kyoto, Japan. kkawada@kuhp.kyoto-u.ac.jp.
authors.forename: Kenji
authors.initials: K
authors.lastname: Kawada
authors.affiliation: Department of Surgery, Graduate School of Medicine, Kyoto University, 54 Shogoin- Kawara-cho, Sakyo-ku, 606-8507, Kyoto, Japan.
authors.forename: Suguru
authors.initials: S
authors.lastname: Hasegawa
authors.affiliation: Department of Surgery, Shiga Medical Center for Adults, Moriyama, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yamada
authors.affiliation: Department of Surgery, Faculty of Medicine, Kinki University, Osaka Sayama, Japan.
authors.forename: Junichiro
authors.initials: J
authors.lastname: Kawamura
authors.affiliation: Department of Surgery, Graduate School of Medicine, Kyoto University, 54 Shogoin- Kawara-cho, Sakyo-ku, 606-8507, Kyoto, Japan.
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Sakai
mesh_terms: D000230:Adenocarcinoma / Q000556:secondary* / Q000601:surgery; D006801:Humans; D010535:Laparoscopy; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D011379:Prognosis; D012004:Rectal Neoplasms / Q000473:pathology* / Q000601:surgery; D014057:Tomography, X-Ray Computed