High rectal cancer with possible extension to the peritoneal reflection.
Findings:
There is a 4 cm long circumferential high rectal neoplasm with distal edge > 10 cm proximal to the anorectal junction. The lesion is centered opposite the S1/2 disc space well distant from the anal sphincter complex.
There is low signal tumor extension into the surrounding mesorectal fat over a distance of 12 mm.
No tumor within 1mm of the mesorectal fascia.
Low signal soft tissue in the mesorectal fat contacts the anterior peritoneal reflection along the proximal aspect of the tumor.
There are > 4 multiple abnormal lymph nodes within the mesorectal fat.
There is no evidence of direct venous invasion.
No iliac chain adenopathy to the level of aortic bifurcation. No pelvic sidewall adenopathy.
Normal marrow signal.
Small left hip effusion.
Impression:
T3c MRF- vs T4a N2 M1 high rectal cancer as above. Low signal soft tissue in the mesorectal fat contacts the anterior peritoneal reflection along the proximal aspect of the tumor.
Step 1: Size and location.
The tumor (1 remove annotation) is nicely seen on the sagittal image. The straight line distance from the anorectal junction is 9cm (2 remove annotation). The measurement should really be made along the wall of the rectum (which is how positive or negative margins are decided) not via the shortest distance through the lumen. If measuring along the posterior wall the distance would be > 10 cm. High rectal cancer.
Step 2: Depth of invasion
Low signal soft tissue extends from the rectum posteriorly into the mesorectal fat (3 remove annotation). Confirm this diffusion restricts and enhances. This could be desmoplastic reaction but I tend to err on the side of calling it tumor on the initial staging exam. So T3c.
Step 3: Mesorectal fascia
The yellow arrow in 4 (remove annotation) points to the anterior mesorectal fascia. The red arrows point to the anterior peritoneal reflection. The tumor straddles the peritoneal reflection.
I think this thin line anteriorly (5 remove annotation) is the anterior peritoneal reflection on the axial images. It cross references to the same location as the line indicated as the red arrow in 4 (remove annotation).
More proximally there is low signal soft tissue in the anterior mesorectal fat (7 remove annotation) which contacts the anterior peritoneal reflection. This soft tissue diffusion restricts (8 remove annotation) and enhances. Contacting the peritoneal reflection would be T4a disease.
Step 4: Adenopathy
There are at least 4 nodes in the mesorectal fat larger than 5mm that are round and heterogeneous.
Step 5: Macroscopic vascular invasion
No definite evidence of EMVI.
Step 6: Incidental findings
None.
The decision to suggest T4a disease in this case had little consequence. First, I know our surgeon would resect that because there was no extension through the reflection. Secondly, this patient had liver metastases so would be receiving neo-adjuvant chemotherapy.
The plan was to provide neoadjuvant treatment, resect the liver metastases, then resect the rectal tumor. During therapy the liver disease worsened so the patient was placed on palliative chemotherapy.