I was created a product.info.extrahint page.
Here is my frontend layout :
<catalog_product_view>
<reference name="product.info.extrahint">
<block type="***_***/product" name="***_product" template="***/***/product.phtml" />
</reference>
</catalog_product_view>
My product.php extended from Mage_Catalog_Block_Product_Abstract
How to get category name in product.php?
Load product model, then get categories list and echo out the ones you want?