**4. "The low risk polyp"**

Several authors, starting with Morson in 1984[24], have developed the concept of the low risk polyp. That is, a polyp which can be safely treated with polypectomy alone, as there is minimal risk of nodal disease. The concept has been incorporated into the American College of Gastroenterology guide lines[25]. They recommend no further treatment if:

The polyp is considered to be completely excised by the endoscopist and is submitted *in toto* for pathological examination.

In the pathology laboratory, the polyp is fixed and sectioned so that it is possible to accurate‐ ly determine the depth of invasion, grade of differentiation, and completeness of excision of the carcinoma.

The cancer is not poorly differentiated.

pan found lymphatic involvement to be highly significant for nodal metastases (odds ratio 4.69 P<0.0001) in a multivariate analysis of risk factors.[17] They also found that in a small number of cases adverse outcomes were seen from cases of lymphatic invasion, despite in‐

Vascular invasion is also considered difficult to identify, but where present, it is strongly as‐ sociated with nodal disease. Yasuda[18] studied T1 rectal tumours, including specimens from primary resections and resections after polypectomy. The odds ratio for the nodal metastasis with reference to the presence or absence of vascular invasion was 12.023 (3.751– 116.751 p=0.001). Another study of sessile T1 colorectal carcinomas found that vascular inva‐ sion was a significant factor in both univariate and multivariate analysis. However they ad‐ mit that the small number of cases of vascular invasion were found in lesions with deeper

An odds ratio of 7 (2.6–19.2) for lymph node metastasis was reported in the only meta-anal‐ ysis looking specifically at malignant polyps and the presence of vascular invasion.[1] How‐ ever, the same analysis demonstrated no such increased risk in polyps that would otherwise be considered low risk. It may well be that vascular invasion carries no special significance

Tumour budding is the presence of microscopic islands of tumour cells out ahead of the main front of tumour invasion. At present there is no defined agree standard to reporting the phenomenon but several authors have found it to be highly significant. Yasuda reported an odds ratio of 11.11 (3.64–146.03)[18] for predicting nodal disease but until further study

T1 rectal tumours seem to be particularly likely to cause nodal disease, especially when lo‐ cated in the lower third.[15,23] However at this stage there have been no studies looking at

Several authors, starting with Morson in 1984[24], have developed the concept of the low risk polyp. That is, a polyp which can be safely treated with polypectomy alone, as there is minimal risk of nodal disease. The concept has been incorporated into the American College

The polyp is considered to be completely excised by the endoscopist and is submitted *in toto*

of Gastroenterology guide lines[25]. They recommend no further treatment if:

vasion being confined to the head of the polyp (Haggit 1).

146 Colonoscopy and Colorectal Cancer Screening - Future Directions

in itself and should not be emphasised in decision making.

occurs it is difficult to make firm recommendations.

this relationship specifically in malignant polyps.

**4. "The low risk polyp"**

for pathological examination.

Sm3 invasion.[23]

**3.6. Tumour budding**

**3.7. Location**

There is no vascular or lymphatic involvement.

The margin of excision is not involved. Invasion of the stalk of a pedunculated polyp, by itself, is not an unfavourable prognostic finding, as long as the cancer does not extend to the margin of stalk resection.

The European recommendations, while noting the potential of tumour budding and lym‐ phatic and vascular invasion as prognostic factors, decline to provide a guideline as they have not been statistically significant in all cases.[22]

Another perspective is given by Nicholls,[7] who instead offered an algorithmic approach. He differentiates between colonic and rectal polyps. For rectal lesions judged to be adenoma prior to resection he recommends that all poorly differentiated lesions be removed. For co‐ lonic polyps he suggested further resection solely for Haggit 4 polyps (including by defini‐ tion all sessile polyps) with a depth of invasion >1000 µm.

Systematic review of studies which selected low risk polyps using methodology broadly similar to the American criteria has demonstrated very low rates of nodal recurrence. (See Table 4). Mortality from oncological resection varies greatly by age and co-morbidity but is usually quoted around 3-5%.[26-28] Therefore, for these lesions, the safest course of action is surveillance rather than further resection.[8,29]

It should be noted that these criteria take no account of the depth of invasion and that these guidelines would encourage the removal of some lesions that have been safely treated by endoscopy. It may be that they are documenting many of the same characteristics but in a different way. It is not hard to imagine that Sm3 lesions are less likely to be excised with clear margins and are more likely to show poor differentiation. Indeed a large study of sur‐ gically resected sessile T1 colorectal tumours found Sm3 invasion in 68% of G3+4 tumours and on 33% in G1+2 (P=0.001). This study also found tumour grade not to be significant on multivariate analysis.[23]

Given Japanese experience it maybe be better to refine the criteria for a low risk polyp as any polyp lacking all of these features:

High grade (G3-4) lesions.

Incomplete resection or other factors preventing adequate histological assessment of the le‐ sion.

Piecemeal resection

Depth of invasion greater than 2mm from *muscularis mucosa*

Width of invasion greater than 4mm.

The utility of including lymphatic invasion, vascular invasion or tumour budding is unclear at this time. Further work should be done to examine the risk from polyps of the lower third of the rectum, especially as these can often require a permanent stoma if oncological resec‐ tion is performed.

**5. "The high risk polyp"**

**5.1. "First do no harm..."**

vival advantage lies.

Further Resection

with reference to a 2x2 table of results

**5.2. Nodal disease and oncological resection**

for T1-2N2 disease. [30]

Polyps that do not meet the low risk criteria should be considered for surgical removal even if there has been total excision of the primary lesion. Indeed, it is unusual to find residual tumour in the surgical specimen, especially if the lesion had clear histological margins.[6] The justification for surgery is the desire for regional control as the risk of nodal disease is much higher in these patients and oncological resection is required to obtain regional con‐ trol in a similar manner to other colorectal malignancies. The dilemma is that only a minori‐ ty of these patients have nodal disease requiring control and these patients are only reliably identified after resection. Especially in elderly, the decision to resect has the possibility to

It is an old surgical adage that surgery is only indicated if the natural history of the cure is better than the natural history of the disease. In situations of uncertainly like this it is useful to examine the possible outcomes of proposed courses of action in order to see were the sur‐

The outcomes of the decision to operate will be a function of the risk of nodal disease and the risk of operative mortality and morbidity. We feel it is useful to consider these decisions

**Nodal disease**

**Table 5.** 2x2 Table of outcomes from the decision regarding further resection of high risk malignant polyps.

We see no reason to regard these patients as any different from patients who had proceded straight to oncological resection and post operatively were staged either IIIa to IIIc (TNM v5). In the SEER data from 1998 to 2000 there is a huge difference between those with regard to five year survival (73% vs. 28% respectively). Clearly this stage differentiation has huge implications for the advisability of surgery. It has been suggested that T1-2N2 tumours have a better survival that T3-4N2 tumours and the TNMv6 classification has been changed to re‐ flect this. Newer SEER data shows five year survival of 87.7% for T1-2N1 disease and 75%

*Yes No*

disease (roughly 75%) Operative mortality (Variable)

Curative procedure, without operative mortality (Roughly 100%)

The Malignant Polyp: Polypectomy or Surgical Resection?

http://dx.doi.org/10.5772/52865

149

cause considerable harm without producing a benefit to the patient.

*Yes* Survival similar to resested Stage IIIa

*No* Survival as for stage IV disease (Roughly 5%)


**Table 4.** Incidence of Adverse Outcome in Low Risk Polyps. Low risk = Low risk = excision complete with resection margins of at least 2 mm, no Grade 3 carcinoma, and no vascular invasion. (From Sitz et al. 2004)
