Frequency of Carcinoma in Adenomas < 1 cm14791.3% 1-2 cm5809.5% > 2 cm43046.0% Muto et al 1975
Frequency of Carcinoma in Adenomas tubular18754.7% tubulovillous38022.4% villous23441.9% Muto et al 1975
Frequency of Carcinoma in Adenomas mild dysplasia17345.7% moderate dysplasia54918.0% severe dysplasia22334.5% Muto et al 1975
High Risk (‘Advanced’) Adenomas > 1 cm villous component severe dysplasia
As long as there is no invasive malignancy and excision is complete - No worries!
Rectosigmoid Adenoma Follow-Up 1618 patients followed for a mean of 14 years after removal of rectosigmoid adenomas: 49 (3%) developed colorectal cancer: 14 rectalSIR 1.2 (CI 0.7-2.1) (11/14 had incompletely excised adenomas) 35 colonic SIR 2.1 (CI 1.5-3.0) Atkin et al 1992
Risk of Subsequent Colon Cancer tubular1mild1.3 tubulovillous3.8moderate3.4 villous5.0severe3.3 <1 cm1.5 1 tumour1.7 1-2 cm2.2>2 tumours 4.8 >2 cm5.9
Risk of Subsequent Colon Cancer PatientsCancersSIR Low Risk Adenomas Single71240.6 Multiple6400 Total77640.5 High Risk Adenomas Single683202.9 Multiple159116.6 Total842313.6
Advanced Adenoma Patients > 1 cm villous component severe dysplasia multiple polyps
Even if there is no invasive malignancy and excision is complete - Grading of dysplasia and assessment of villousness in adenomas that are <10mm will govern surveillance So we’ve got to try hard to get it right!
Grading Dysplasia in 2189 Adenomas at 13 Centres minmaxmedian mild 29%88%42% moderate 10%67%43% severe 1%24%4%
High Grade Dysplasia Expected in <5% of all adenomas Equates to ‘intramucosal adenocarcinoma’ Involves more than 1-2 glands
High Grade Dysplasia Recognition based primarily on ARCHITECTURE: COMPLEX glandular crowding and irregularity PROMINENT budding CRIBRIFORM ‘back-to-back’ glands INTRALUMINAL papillary tufting Low power diagnosis - epithelium is thick, blue, disorganised and ‘dirty’
High Grade Dysplasia CYTOLOGY: Loss of polarity and nuclear stratification Markedly enlarged nuclei Atypical mitoses Prominent apoptosis Usually more than one of these
Flat Adenomas –thickness does not exceed twice that of adjacent mucosa –more often right sided –usually small (<1cm) with tubular growth pattern –more often high grade dysplasia –40% contain carcinoma –uncommon because no chromoendoscopy Muto et al 1985
National Polyp Study 1418 patients Complete colonoscopy with removal of adenomas No special attempt to identify flat adenomas Follow up colonoscopy, mean 5.9 years 97% clinical follow up, 80% colonoscopies 8401 patient years
National Polyp Study 90% reduction in colorectal cancer incidence all five colorectal cancers found on follow-up were polypoid
Macroscopic Examination & Trimming of Polyps Size - to nearest millimetre in formalin fixed specimen (whole polyps) Polypoid lesions Fixed intact Bisect through stalk if <10mm If larger, trim to leave central intact stalk At least three levels of stalk Sessile lesions pinned out and all-embedded after inking margins
Hyperplastic Polyp Increase in frequency with age 17 times commoner in colons with carcinoma Similar dietary and lifestyle risk factors to CRC K-ras mutation common Clonal Monocryptal?
Serrated Adenoma Dysplasia by definition Eosinophilic cytoplasm Pseudostratified, ‘pencillate’ nuclei May be tubular, tubulovillous or villous Invade to give serrated carcinoma Longacre & Fenoglio-Preiser 1990
Sessile Serrated Polyp (Adenoma) Serrated polyps with unusual architectural features No conventional dysplasia but may have ‘nuclear atypia’ or ‘hypermucinous’ change Right colon Females > males Large sessile, poorly defined Torlakovic & Snover 1996