A method of forming and enlarging a percutaneous penetration is provided. The method includes the step of providing a radially expandable dilation assembly having a needle assembly removably inserted in a axial lumen thereof. The radially expandable dilation assembly includes a radially expandable sleeve body defining a lumen and an introducer seal disposed across the lumen and defining an opening formed therein. The method further includes the steps of penetrating the radially expandable dilation assembly and needle assembly through tissue to a target surgical site, withdrawing the needle assembly from the radially expandable dilation assembly, and inserting an expansion assembly through the opening formed in the introducer seal and into the axial lumen of the radially expandable dilation assembly.
