Rectal cancer - T2 with incidental ejaculatory duct cyst on MRI

Case contributed by Vikas Shah


Rectal bleeding. Sigmoidoscopy and biopsy confirm rectal adenocarcinoma. Staging MRI.

Patient Data

Age: 65 years
Gender: Male

Length of tumor: 3 cm

Distance from distal edge of tumor to anorectal junction: 3 cm

Distance from distal edge of tumor to anal verge: 6 cm

Tumor relationship to peritoneal reflection: below

Tumor morphology: semi-annular

Invasive margins (clock face terminology): 11 to 1 o'clock

T stage (and which organs involved if T4b): T1/2 with no penetration of muscularis propria

Depth of tumor invasion (less or greater than 5 mm): less than 5 mm

Shortest distance to mesorectal fascia or levator muscle: 3 mm

Extramural venous invasion: none

Tumor deposits: none

Mesorectal lymph nodes: yes, 3

Extramesorectal lymph nodes: none

For low cancers, involvement of anal sphincter muscles or intersphincteric fat: N/A


Summary: Anterior mid rectal cancer, confined to rectal wall. Stage T1/2 N1 V0, CRM clear.

There is an incidental round structure arising from base of the prostate, situated between the seminal vesicles. It is high signal on T2 weighted images and is an ejaculatory duct cyst.

Annotated images

Annotated image

Red arrows indicate peritoneal reflection:

  • peritoneum reflecting off anterior wall of upper rectum on sagittal image, with rectum below this level being enclosed within the mesorectal compartment, and above this level and increasing area of the rectum becomes covered by the peritoneum
  • on the coronal image, the peritoneal reflection is seen as an inverted Y reflecting off the anterior rectal wall

Blue arrows indicate mesorectal fascia:

  • shown here to surround the rectum on sagittal, axial and coronal images
  • posteriorly, the mesorectal fascia is distinct and anterior to the presacral fascia
  • it is not seen clearly anteriorly due to it abutting the posterior margin of the prostate and Denonvillier's fascia
  • lateral to the mesorectal fascia lie the pelvic sidewalls

Case Discussion

As well as showing what a semi-annular mid rectal cancer confined to the wall looks like, this study also shows what the normal mesorectal fascia and peritoneal reflection look like. These are important anatomic features to be aware of when reporting rectal cancer MRI.

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