Mesh manipulation : My object is in the field of view but Unity thinks it's not

Hello,

I am meeting a very interesting issue about mesh manipulation and rendering.

I have a basic square-shaped plane. I need to make it match with my area size, so I move vertices to make the plane at the correct size. The problem comes when Unity computes which object should be rendered beacause it is in the camera's field of view. Unity considers the size and position of my origin basic square, and not the size of my actual mesh, with modified vertices.

This picture will be more clear :

If the size of the basic square is out of the field of view, so the object is not rendered, even if a part of it is actually in the field of view.

I have no idea how to tell Unity to reconsider the mesh size, and I meet some difficulty when I try to formulate Google requests about this.

Does someone know what I should do ? Thank you for your help.