Low rectal cancer with involvement of the sphincter complex.
There is a 5cm low rectal cancer with distal margin 3 cm below the ano-rectal junction, 3 cm from the anal verge.
The tumor invades through the internal spincter and into the inter-sphenteric plane on bilaterally. There is no invasion trough the external sphincter.
Just above the ano-rectal junction there is 5mm of direct extent of tumor into the mesorectal fat on the left.
No adenopathy on the provided images which do not include the entire mesorectum.
No evidence of macroscopic vascular invasion.
Impression
T3c MRF- low rectal cancer extends for a distance of 3cm below the ano-rectal junction and extends through the internal anal sphincter into the intershpincteric plane bilaterally.
Insufficient images for nodal assessment.
Step 1: Size and location.
The proximal end of the tumor on the axial T2 and post contrast images is here (1 remove annotations, 2 remove annotations). On the coronal images the proximal end is here (3 remove annotations).
The distal end is beneath the level of the ano-rectal junction on the sagittal images (4 remove annotations).
Because the tumor is near the ano-rectal junction on the sagittal images we need to use the images parallel to the anus to accurately define the tumor in relation to the anal sphincter complex.
The inferior aspect of the tumor (red arrow in 5 remove annotations) is approximately 3 cm distal to the location where the levator ani joins the internal sphincter (imaginary line between the blue arrows in 5 remove annotations). Note this person has a long anus, I measure it at 6 cm (6 remove annotations, see ano-rectal junction as blue arrows).
This tumor has invaded through the anal mucosa and into the sphincter. It extends through the internal sphincter at multiple locations. At the level of the levator plate the internal sphincter (solid yellow line in 7 remove annotations) is discontinuous (dashed yellow line in 7 remove annotations) anteriorly and laterally on both the left and right.
On the post contrast images a bit higher you can really see the tumor extend through the internal sphincter on the left (8 remove annotations).
More inferiorly you can see the tumor invade through the fat (yellow line in 9 remove annotations) in the intersphincteric plane on the right and into the external sphincter.
This can also be seen nicely in the coronal plane (10 remove annotations and 11 remove annotations).
Step 2: Depth of invasion
Just above the ano-rectal junction there is approximately 5mm of direct extent of tumor into the mesorectal fat on the left (red arrow in 12 remove annotations).
The left lateral wall of the distal rectum (yellow line in 13 remove annotations) is also discontinuous at this site. This is T3c disease.
Step 3: Mesorectal fascia
None of this disease comes within 1mm of the levator, so this is MRF- disease.
Step 4: Adenopathy
I've not included T2 images through the entire mesocolon so we will not discuss nodes in this case.
Step 5: Macroscopic vascular invasion
None.
Step 6: Incidental findings
None.
This case was included as a great example of using the images parallel to the anus to evaluate tumor extension into the anus and its relation to the sphincters.
This patient will require neoadjuvant chemotherapy, long course radiation therapy, and an abdomino-perineal resection.