The mesorectum is the fatty tissue surrounding the rectum, enclosed within the visceral mesorectal fascia. It contains:
- Blood vessels
- Lymphatics
- Lymph nodes
- Connective tissue
It is the primary route of local spread for rectal cancer. Hence, complete removal of the mesorectum during Total Mesorectal Excision (TME) is critical to reduce recurrence and improve survival.
Clinical Significance
- Gold standard surgery for rectal cancer
- Sharp dissection outside the mesorectal fascia (Waldeyer’s fascia)
- Removes rectum + mesorectum + regional lymph nodes
- Improves survival: 5-year survival ↑ from 48% to 68%
- Reduces recurrence:
- From 20–30% → 8–10%
- With adjuvant therapy → as low as 2.6%
Macroscopic Grading of Mesorectum
| Grading | Description |
|---|---|
| Complete (Grade 3)- Good surgery | Bulky, smooth mesorectum, no coning, no defects >5 mm, smooth CRM |
| Nearly complete (Grade 2)- Moderate | Moderate bulk, defects >5 mm but not reaching muscularis propria, no exposed muscle |
| Incomplete (Grade 3)- Poor surgery | Little bulk, defects exposing muscularis propria, irregular CRM |
Images to Capture
- Fresh specimen (anterior + posterior views)
- All slices laid sequentially (proximal → distal)
- Close-ups of:
- Tumor near radial margin
- CRM defects
- Lymph node involvement
Grossing Template – TME Specimen
Specimen Handling
- Specimen received fresh & unopened
- Photograph specimen (anterior/posterior)
- Open anteriorly, just above and below tumor
- Insert formalin-soaked gauze in ends
- Fix 72–96 hrs in formalin
Measurements & Description
| Parameter | Description |
|---|---|
| Length of rectum | ______ cm |
| Mesorectal envelope | Describe bulk, defects, smoothness |
| Coning* | Present / Absent |
| Tumor size | ______ cm (L × W × Depth) |
| Distance to margins | Proximal: ___ cm, Distal: ___ cm |
| Tumor location | Above/below/anterior/posterior reflection |
| Radial margin (CRM) | Closest point, smooth/moderate/very irregular |
*Coning refers to the tapering of the mesorectum toward the distal end of the specimen. It indicates loss of mesorectal bulk and may reflect poor surgical technique, increasing the risk of positive margins and recurrence.
Sectioning Protocol
- Transverse slices every 3–5 mm
- Maintain anatomic orientation
- Describe:
- Tumor extent
- Depth of invasion
- Relationship to serosa, radial margin
- Presence of nodes, distance to margin
- Additional findings (polyps, diverticula)
Tissue Submission
| Tissue/Region | Sectioning Guideline |
|---|---|
| Tumor | Entire (≤5 blocks) or 1/cm |
| Deepest invasion | ≥2 blocks |
| Radial margin (CRM) | ≥2 blocks |
| Peritoneal relation | ≥2 blocks |
| Treated tumor site | ≥5 blocks including scar (post-neoadjuvant) |
| Proximal/Distal margins | En face |
| All lymph nodes | In entirety; note bisected/trisected |
| Apical node | Submit separately if identified |
| Positive nodes near CRM | Note distance and clock position |
Pathologic Prognosticators
| Feature | Importance |
|---|---|
| CRM positivity <1 mm | ↑ Local recurrence, ↓ survival |
| EMVI / PNI | Associated with metastasis |
| Tumor Budding | Indicates aggressive behavior |
| Lymph node yield ≥12 | TNM staging quality benchmark |
| Regression score (TRG) | TRG 0 = Best prognosis |
| MLNR (Metastatic Lymph Node Ratio) | Emerging alternative staging metric |
| Acellular mucin | Not considered viable tumor |
References
Watch a complete video explanation:
Leave a Reply