Intramural metastasis of T1 rectal cancer: report of a case report

BACKGROUND: Intramural metastasis (IM) is extremely rare in colorectal cancer, although it often occurred in esophageal cancer. CASE PRESENTATION: 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.