  In this paper, we characterize finite group $G$ with unique proper
non-abelian element centralizer. This improves \cite[Theorem 1.1]{nab}. Among
other results, we have proved that if $C(a)$ is the proper non-abelian element
centralizer of $G$ for some $a \in G$, then $\frac{C(a)}{Z(G)}$ is the Fitting
subgroup of $\frac{G}{Z(G)}$, $C(a)$ is the Fitting subgroup of $G$ and $G' \in
C(a)$, where $G'$ is the commutator subgroup of $G$.
