Glands may permeate muscle but no desmoplastic response
Desmoplastic response usually present
Lamina propria may be retained around entrapped glands
No retained lamina propria around infiltrating glands
Glands frequently have a mixed population of cell types - mucus, goblet, paneth cells
Monomorphic population
Expression of MUC1 or MUC5AC has been suggested as favoring carcinoma over normal small intestinal mucosa (Zhang 2007)
One report, however, describes basal staining of normal mucosa with MUC1 (Matsubayashi)
MUC5AC stains normal goblet cells and gastric metaplasia
Ultimately, the diagnosis of carcinoma must be made on morphologic grounds
Positivity may suggest rebiopsy in a marginal specimen
See Special Studies for complete staining results
Grading / Staging
Grading
WHO accepts grading simply as Low vs. High grade
CAP protocol requires well, moderately, poorly differentiated and undifferentiated designations
Low grade ≥50% gland forming
Well differentiated
>95% gland forming
Moderately differentiated
50-95% gland forming
High grade <50% gland forming
Poorly differentiated
5-49% gland forming
Signet ring (>50% of cells signet ring)
Undifferentiated
<5% gland forming
Staging
Use TNM staging:
Ampulla and peri-ampullary
is different from rest of small intestine including duodenum
Tis
Carcinoma in situ (no lamina propria invasion)
T1
Confined to ampulla and sphincter of Oddi
T2
Invasion of duodenal wall
T3
Invasion of pancreas
T4
Peripancreatic soft tissue or other organs/structures
Size of tumor is not included in TNM but is predictive
<2.5 cm has 85% 5 year survival
≥2.5 cm has 20% 5 year survival
Small intestine other than ampulla:
Tis
Carcinoma in situ (no lamina propria invasion)
T1
Lamina propria or submucosal invasion
T2
Invasion of muscularis propria
T3
Through muscularis propria ≤2 cm into subserosa, mesentery or retroperitoneum
T4
Invasion >2 cm, serosal perforation, or into other organs/tissues including pancreas
For ampulla, regional nodes include:
Superior and inferior to head and body of pancreas
Anterior and posterior pancreaticoduodenal
Proximal and superior mesenteric
Pyloric, pancreaticoduodenal, common bile duct or pericholedochal
Hepatic artery nodes, infrapyloric, subpyloric
Celiac, retroperitoneal, and lateral aortic
Miscellaneous TNM issues
Multiple simultaneous carcinomas
Includes those diagnosed within 2 months
Includes Tis lesions
TNM should be reported for the lesion with the highest T score
Add (m) or (2) etc. to indicate number of primary lesions e.g. pT3(m)
Post-neoadjuvant therapy excision specimens
TNM as usual but add prefix, e.g. ypT1
Pools of mucin without epithelial cells are counted as negative at both the primary site and in lymph nodes
Residual tumor in patient at end of surgical excision
Either distant or at positive surgical margin
Positive margin generally is interpreted as indication of residual neoplasm but should be discussed with surgeon
Designate as R1 if microscopic
Designate as R2 if macroscopic
Recurrences
Coded as rpT1 etc.
Use usual TNM guidelines as for primary
Label recurrence as located in proximal segment of anastomosis, except when that is ileum following a right colon resection
Bibliography
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