Yes the skin texture.

Next I'll go through how to make a hole through the chest, This is obviously not the section you want masked but it will clearly illustrate the method. You can then easily refine it to mask off the section you require.

Start by creating two new layers.

On the top new layer use any of the painting tools to draw a large black circle over the chest area.

On the lower new layer flood fill with white.

You should now have a large black dot on a white background.

Go to the Photoshop menu and select "Save for web" Follow the dialogs and save the image as "your_figure_transparency_mask.jpg"

Into Poser click the Material tab

Mouse over the figure, the cursor changes to an eyedropper, select the chest area.

In the material pallet window right click an empty area, then from the pop up menu that appears select New Node > 2D texture > image_map. Browse for your_figure_transparency_mask.jpg

In the new node window that appears click on the small plug icon top left and drag it to the small socket icon displayed to the right of "Transparency" in the main Poser Surface material node.

Set that transparency value to 1.000

Does a hole appear in your figure?

Compare what you have with my screen shot above.