Background: Unlike other solid tumors, tumor size (TS) is not a part of the TNM staging system for colon cancer. Our goal is to correlate TS with TNM staging, nodal positivity (NP), and 5-year overall survival (OS) for patients (pts) with invasive colon cancer undergoing sentinel lymph node mapping (SLNM) vs. conventional surgery (CS). Methods: A retrospective review of 681 pts with invasive adenocarcinoma of the colon were reviewed and divided into two groups of pts (SLNM and CS). These groups were subdivided according to the size of the tumor in four groups (0-2, 2-4, 4-6 and more than 6 cm). 461 pts underwent SLNM between 1996-2010 compared to 220 pts who underwent CS between 1996-2006. The pathology reports reviewed for TS (the maximum diameter of the primary tumor), T staging, and NP. The OS was calculated from the social security database. Then all data was compared between both groups. Results: Pts with tumors <2cm were mainly T1+T2 (72%, 70%), whereas tumors >6 cm, majority of pts wereT3+T4 (94%, 85%). T1+T2 percentage consistently decreased as TS increased, and T3+T4 percentage was increasing consistently with increased TS (Table 1A). NP according to TS for SLNM pts were (16%, 53%, 56%, 48%) NP and for CS pts were (15%, 32%, 34%, 39%). In both groups, NP increased as TS increased compared to 0-2 cm group. The overall NP in both groups was 47% and 31% (Table 1B). OS for SLNM and CS pts were calculated in each group according to TS. Overall SLNM pts had better OS when compared to CS pts (65 %, 54%). Conclusions: Increasing TS was consistent with increasing T staging for both SLNM and CS pts. NP and OS were worse with increased TS for SLNM and CS pts. SLNM pts had higher NP and better outcome in OS when compared to CS pts, hence TS should be considered as a prognostic factor in pts with adenocarcinoma of the colon.

1A	SLNM		Conventional surgery
Size CM	T1+T2	T3+T4	T1+T2	T3+T4
0-2	60 (72%)	23 (38%)	24 (70%)	10 (30%)
2-4	54 (30%)	121 (70%)	28 (38%)	46 (62%)
4-6	20 (16%)	104 (86%)	11 (16%)	57 (84%)
>6	5 (6%)	74 (94%)	7 (16%)	37 (84%)

1B	SLNM		Conventional surgery
Size CM	Nodal Positivity	5 year overall survival	Nodal Positivity	5 year overall survival
0-2	16%	81%	15%	71%
2-4	54%	66%	32%	55%
4-6	56%	56%	34%	49%
>6	48%	52%	39%	49%
Total	47%	62%	31%	54%