Border: pushing/infiltrative. Lymphocytic reaction: prominent/sparse.
An expanding growth pattern/margin with a Crohn's-like inflammatory response is a better prognostic indicator than an infiltrating, irregular margin with no inflammation.
Degree of mesorectal/mesocolic spread from the outer border of the muscularis propria (>5mm) seems to influence prognosis but is not well established.
When the mesocolic or mesorectal circumferential radial margin is involved the degree of tumour spread is an indicator of either advanced disease or alternatively inadequate surgery.
pTis carcinoma in situ: intraepithelial (within basement membrane) or invasion of lamina propria (intramucosal) with no extension through muscularis mucosae into submucosa pT1 tumour invades submucosa pT2 tumour invades muscularis propria pT3 tumour invades beyond muscularis propria into subserosa or non-peritonealized pericolic/perirectal tissues pT4 tumour invades the serosal surface or adjacent organs and/or perforation of visceral peritoneum*.
Serosal involvement is tumour either at or ulcerating the serosal surface as this is prognostically worse than tumour in a subserosal inflammatory reaction—about 10% of patients develop peritoneal or ovarian (Krukenberg) deposits and there is a higher rate of distant metastases than in direct invasion of adjacent organs or structures alone. Serosal pT4 disease may include direct involvement of other segments of colon, e.g. sigmoid colon by a caecal carcinoma. If no tumour is present in adhesions to other structures, e.g. bladder, classify as pT3. Separate omental deposits are metastatic (pM1) disease.
In low rectal cancer involvement of sphincteric muscle is pT3 and levator ani muscle is pT4.
Intramural extension to adjacent bowel, e.g. caecal carcinoma to ileum, does not affect the pT stage.
A minimum of five blocks of tumour and bowel wall is necessary to assess the pT stage adequately and to find extramural vascular invasion. The specimen is cut into serial transverse slices 4-5 mm thick, laid out in order and relevant slices selected for blocking.
Multiple carcinomas should be assessed and staged individually.
*Optional descriptors: pT4a (other organs/structures), pT4b (visceral peritoneum).
The upper anterior rectum is invested in peritoneum
The anterior mesorectum is thinner (0.75 - 1 cm) than the posterior mesorectum (1.5 - 3 cm) Cut the resection specimen into multiple serial transverse slices about 5 mm thick Blocks for histology are: Above the reflection A tumour, rectal wall and serosa B tumour, rectal wall and serosa tumour, rectal wall and mesentery At the reflection C tumour, rectal wall and serosa tumour, rectal wall and mesorectum Below the reflection D tumour, rectal wall and mesorectum
D1 distance (mm) of the deepest point of continuous tumour extension to the nearest point of the painted CRM D2 distance (mm) of the deepest point of discontinous tumour extension (or in a lymphatic, node or vessel) to the nearest point of the painted CRM
Direct implantation spread can be seen at anastomoses, peritoneal and abdominal wall wounds. Anastomotic site recurrence is unusual if the longitudinal margin clearance in the primary specimen is >5cm.
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