What are some of the themes in "The Cask of Amontillado" by Edgar Allan Poe?

I will give you two themes I think are important to the story. They are in no particular order.

One theme of Poe's "The Cask of Amontillado" is revenge. This should be a fairly obvious theme. Fortunato hurt and wronged Montresor in some way. The reader is not given specific details about it. Montresor vows revenge, and the rest of the story is about the execution of his plan for revenge.

The thousand injuries of Fortunato I had borne as I best could; but when he ventured upon insult, I vowed revenge.

Unfortunately for Fortunato, Montresor's revenge plot ends with Fortunato's death.  

Another theme is betrayal. Based on the opening line of the piece, readers can assume Montresor and Fortunato had some level of mutual respect for each other. In order for Montresor to be hurt badly enough to vow murderous revenge, at some point he and Fortunato must have had some level of trust in each other. Fortunato betrayed that trust, but the betrayal doesn't end with Fortunato. Montresor also betrays Fortunato's trust when he lures Fortunato to his horrible death.