Here’s the solution/hack I ended up using:
<?php
$category = $wp_query->get_queried_object();
$parent = ($category->category_parent) ? $category->category_parent : $cat;
$parents = get_category_parents($parent, TRUE, ' ', FALSE);
$end = ' ';
$pos_start = strpos($parents, $end) ;
$pos_end = strpos($parents, $end, ($pos_start+1));
if ($pos_end === false) {
echo $parents; }
else {
echo substr($parents, ($pos_start), ($pos_end));
} ?>