sure...
I do it like this for my categories:
<div id="breadcrumbs">
<a href="<?php echo get_bloginfo('url'); ?>" title="">Home</a>
<?php
$breadcrumbs = explode('|',get_category_parents($cat,true,'|'));
array_pop($breadcrumbs);
array_pop($breadcrumbs);
if ($breadcrumbs) foreach ($breadcrumbs as $crumb) echo ' / '.$crumb;
?>
</div>
<h1><?php single_cat_title(); ?></h1>
That takes the current category off the end, and returns true on the last line only if your category has parents (and/or grandparents, etc.)
if you don't want to remove the category you're in now, just remove one of those array_pop lines. I remove the current category so I can put it into that h1 tag underneath. You can see it working on my blog.
if you just wanted to check for the top-level parent, you would just need to look at the first element in the $breadcrumbs array.
if ($breadcrumbs) echo $breadcrumbs[0];
hope that helps.