  Based on $(27.12\pm 0.14)\times 10^{8}$ $\psi(2S)$ events collected with the
BESIII detector, we search for the decay $\eta_c (2S) \rightarrow \pi^{+}
\pi^{-} \eta_c$ with $\eta_c\rightarrow K_S^0 K^{\pm}\pi^{\mp}$ and
$\eta_c\rightarrow K^{+}K^{-}\pi^{0}$. No significant signal is observed, and
the upper limit on the product branching fraction
$\mathcal{B}(\psi(2S)\rightarrow \gamma \eta_{c}(2S))\times\mathcal{B}$($\eta_c
(2S) \rightarrow \pi^{+} \pi^{-} \eta_c$) is determined to be
$2.21\times10^{-5}$ at the 90\% confidence level. In addition, the analysis of
the process $\psi(2S)\to\gamma \eta_{c}(2S), \eta_{c}(2S)\rightarrow
\pi^{+}\pi^{-}K^{0}_{S}K^{\pm}\pi^{\mp}$ gives a clear $\eta_c(2S)$ signal with
a statistical significance of $10\sigma$ for the first time, %The product
branching fraction $\mathcal{B}(\psi(2S)\rightarrow \gamma
\eta_{c}(2S))\times\mathcal{B}(\eta_{c}(2S)\rightarrow
\pi^{+}\pi^{-}K^{0}_{S}K\pi) $ is measured to be $(9.31 \pm 0.72 \pm
2.77)\times 10^{-6}$, and and the branching fraction
$\mathcal{B}(\eta_{c}(2S)\rightarrow \pi^{+}\pi^{-}K^{0}_{S}K^{\pm}\pi^{\mp})$
is determined to be ($1.33 \pm 0.11 \pm 0.4 \pm 0.95 $)$\times 10^{-2}$, where
the first uncertainty is statistical, the second is systematic, and the third
uncertainty is due to the quoted $\mathcal{B}(\psi(2S)\rightarrow \gamma
\eta_{c}(2S))$.
