Lemma without numbering

I want to use the lemma environment without numbering because I only have one lemma. If I use the package \newtheorem{lemma}{Lemma} I get "Lemma 1" in Italics. And if I do

\usepackage{amsthm}
\newtheorem*{lemma}{Lemma}    

I get "Lemma" but in bold and plain font. I want the Italics but without the number. What should I do?