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

There have been few reports of intramural metastasis (IM) of rectal cancer, although IM has been frequently reported and considered to be one of the most important prognostic factors in esophageal cancer [1‐3]. Consequently, it is unclear about the clinical significance and the treatment strategy of IM in rectal cancer. We believe this is the first report of the T1 rectal cancer with IM.

A 62-year-old man was admitted to our hospital for the treatment of rectal tumor incidentally found by rectal examination during a routine medical checkup. The patient had no previous history of malignancy. Colonoscopy revealed a type II rectal tumor of 2 cm in diameter located 5 cm proximal to the anal verge and a submucosal tumor of 1 cm in diameter approximately 1.5 cm proximal to the rectal cancer. In addition, a small adenomatous polyp was observed near the rectal cancer (Fig. 1a). The biopsy of the rectal tumor was suggestive of moderately differentiated adenocarcinoma. The biopsy of the submucosal tumor was not performed because it was thought to be included within the region planned for surgical resection against the rectal cancer. Transrectal ultrasonography suggested the invasion depth of rectal cancer was the deep layer of the submucosa but not the muscularis propria (Fig. 1b). Abdominal CT showed there was no evidence of metastasis to regional lymph nodes or distant organs (data not shown). Barium enema examination suggested a small tumor with an irregular surface and a smaller submucosal tumor with a smooth surface located at the anterior wall of the rectum (Fig. 1c). MRI showed that the rectal cancer was located at the anterior wall of the rectum without invasion into the prostate (Fig. 1d), and diffusion-weighted imaging (DWI) that showed a high signal intensity was accumulated into the rectal cancer (data not shown). Results of laboratory blood tests, including tumor markers, were within normal ranges. Collectively, we preoperatively diagnosed cStage I rectal cancer and performed laparoscopic intersphincteric resection (ISR).

Macroscopic analysis of resected specimens revealed a 16 × 15-mm type II rectal cancer with an irregular surface, a 10 × 10-mm submucosal tumor located 15 mm proximal to the primary rectal cancer, and a 10 × 7-mm adenomatous polyp located 20 mm proximal to the primary rectal cancer (Fig. 2a, b). Histopathological analysis revealed that the primary rectal cancer was moderately differentiated adenocarcinoma with severe lymphovascular invasion: pT1 (submucosal invasion depth 3500 μm), pN0, pM0, ly1, v3, and pStage I. Immunohistochemical analysis using the stainings of D2-40 and Victoria blue was performed to evaluate lymphatic and vascular invasion (Fig. 3a–c). The submucosal tumor was composed of moderately differentiated adenocarcinoma proliferating within the muscularis propria. Moreover, numerous tumor emboli within vascular, but not lymphatic, vessels were observed in regions surrounding the submucosal tumor (Fig. 3d–f). We diagnosed the submucosal tumor to be an IM of the primary rectal cancer based on the following observations: (1) distinct location from the rectal cancer, (2) the gross appearance of the submucosal tumor without intraepithelial cancer extension, (3) the same histological type as the primary rectal cancer, and (4) tumor emboli within vascular vessels observed in regions surrounding the submucosal tumor as well as the primary rectal cancer. Three weeks after the operation, the patient was discharged without any event. The stage of the rectal cancer was stage I, but the patient elected to undergo adjuvant therapy because IM is one of the poorer prognostic factors in esophageal and gastric cancers [1‐4]. Adjuvant chemotherapy (UFT + LV) was administered for 6 months postoperatively. The patient has been followed for more than 4 years without any signs of recurrence.

We report a case of rectal cancer with IM. IM of rectal cancer is extremely rare; however, careful observation of the residual rectum around the primary tumor should be conducted, even in early rectal cancer. Preoperative diagnosis of IM may help to decide therapeutic strategy.

Written informed consent was obtained from the patient for publication of this case report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of the journal.