500
While controversial, trials (subgroup analysis of CALGB 9633 and JBR.10) indicate that Stage IB patients with this feature may benefit from adjuvant chemotherapy.
What is tumor size >4cm? Remember, Stage IB is pT2aN0 (size 3-5 cm). Other high risk features: poorly differentiated tumors, vascular invasion, visceral pleural involvement, wedge resection