XSLT beginner query

I have a few similar XML structures, which I want to be able to process properly in XSLT, so users can view online.

The first:

<TABLETYPE TYPEABBRV="MTHPRTSTS" TOTALINDICATOR="N">
      <CATEGORY TYPE="DISABSTATUS" VALUE="WDIS" />
      <STATUS>MET</STATUS> 
   </TABLETYPE>

The next:

<TABLETYPE TYPEABBRV="ELEMIDADNIND">
  <STATUS>METADDIND</STATUS>
</TABLETYPE>

What I'd like to do is make sure when "STATUS" is displayed I don't get the value from both by checking for the existence of "CATEGORY". If "CATEGORY" exists, output one block of code. If not, a different block. I know I should use "xsl:choose" and "xsl:when" but can't figure out how to test if "CATEGORY" exists. Thank you in advance for viewing and answering.