Low rectal cancer.
Findings:
There is a 1.5 x 1.5 x 1.2 cm low rectal neoplasm with distal margin 3 cm from the ano-rectal junction.
The neoplasm is contained within the wall of the rectum. No extension into the mesorectal fat.
No extension into or involvement of the anal sphincter complex.
No evidence of macroscopic vascular invasion.
No adenopathy. No deep pelvic or pelvic sidewall lymphadenopathy.
Normal marrow signal within the proximal femurs, bony pelvis, and lower lumbar spine.
The uterus has been removed. Neither ovary is confidently identified. No adnexal masses.
Impression:
T2 MRF- N0 low rectal cancer without involvement of the anal sphincter complex
Step 1: Size and location.
The tumor was hard to see on the sagittal images (1 remove annotations) but easy to find on the diffusion (2 remove annotations) and post contrast (3 remove annotations) images. Sometimes you need to cross reference these image with the sagittal ones.
The tumor is 3 cm from the anorectal junction as defined by the anterior aspect of the levator on the sagittal images (4 remove annotations).
This is sufficiently far from the anal sphincter that images parallel to the anus are probably not necessary. However, on these images there is no tumor near the level of the anorectal junction as defined by where the levator joins the bowel (blue arrows in 5, remove annotations).
Step 2: Depth of invasion
There are three good axial slices through the tumor and on all of these images there is an intact low signal muscular layer (6 remove annotations, 7 remove annotations, 8 remove annotations). This is therefore either T1 or T2 disease. MRI does not differentiate. It is not T3 disease.
Step 3: Mesorectal fascia
If there is no tumor outside the bowel then there cannot be involvement of the MRF.
Step 4: Adenopathy
There were no suspicious nodes.
Step 5: Macroscopic vascular invasion
No peri-rectal vessels appeared too thick or intermediate signal.
Step 6: Incidental findings
None.
This patient's rectal cancer was discovered on a colonoscopy performed for a colon cancer seen on CT (9 remove annotations, 10 remove annotations). I could not, even in retrospect, find the rectal cancer on the CT.
Surgeons like to have a 5cm tumor free margin on the distal end of their bowel resection. Since this tumor is only 3 cm from the ano-rectal junction this would not be possible even with an ultralow lower anterior resection. She is also high risk because she had two bowel cancers. The surgeon did not want to do a segmental colon resection and potentially risk the blood supply to more distal anastomosis. He also preferred just one surgery on this elderly patient. Therefore she had a total colectomy plus an abdomino-perineal resection with formation of an end ileostomy. She did not undergo neoadjuvant treatment.
Surgical margins were tumor free though she did develop a post operative small bowel obstruction due to adhesions in the pre sacral region.