According to the DSM IV, there is no such thing as a disorder classified as histrionic. There is, however, Narcissistic Personality Disorder. Here's a link:
Unless you're a qualified psychologist, you cannot diagnose this person. I would refrain from assuming this person suffers from a specific disorder, as any psychologist will tell you that it's extremely rare that one suffers from a single disorder. It is much more likely that a person with a personality disorder has symptoms of many. Dealing with someone who has this disorder is extremely difficult. I say this from personal experience. I'm not trying to lecture you, just know that this is a serious claim and if the person truly has a personality disorder of this magnitude, you should feel very sorry for them (but I'm sure he makes that fairly impossible?).
I second what zotamorf62 suggested. Humans are still pack animals and respond to behavioral cues. If he realizes he's getting a rise out of you, and that satisfies him, he'll continue to seek that behavior. Only respond when he genuinely pleases you. Don't give him fake or manufactured compliments.
There is also the fact that this occurs in your workplace. I would encourage you to contact your HR department and find out what behaviors they classify as egregious, or at least ones that deserve a good talking-to. You should never feel threatened or harassed at your workplace. If you do, you have a legitimate claim for this person's supervisor to intervene.