Amneal Pharmaceuticals, Inc Class A Common Stock (AMRX) had the highest return between 2008 and 2010 by a mid-cap US stock, returning 704.4%.

ASSET	YEARS	% RETURN
Amneal Pharmaceuticals, Inc Class A Common Stock (AMRX)	2008-2010	704.4%
Silvercorp Metals (SVM)	2008-2010	325.65%
Northern Oil & Gas (NOG)	2008-2010	318.62%
Imax (IMAX)	2008-2010	312.79%
Boyd Group Services (BGSI)	2008-2010	274.54%
OceanaGold (OGC)	2008-2010	256.19%
Aura Minerals Inc Common Shares (AUGO)	2008-2010	248.97%
Hawkins (HWKN)	2008-2010	223.73%
Axogen (AXGN)	2008-2010	219.01%
Baytex Energy (BTE)	2008-2010	218.75%
Pegasystems (PEGA)	2008-2010	213.78%
Steven Madden (SHOO)	2008-2010	213.36%
Eldorado Gold (EGO)	2008-2010	211.97%
Cirrus Logic (CRUS)	2008-2010	203.8%
First Majestic Silver (AG)	2008-2010	201.87%
Credit Acceptance (CACC)	2008-2010	199.33%
Trex (TREX)	2008-2010	177.31%
ICL Israel Chemicals (ICL)	2008-2010	177.03%
Bausch Health Companies (BHC)	2008-2010	164.84%
ePlus (PLUS)	2008-2010	161.21%
Dorman Products (DORM)	2008-2010	158.86%
Veeco Instruments (VECO)	2008-2010	158.17%
Encore Capital (ECPG)	2008-2010	143.01%
EZCORP (EZPW)	2008-2010	140.94%
Aya Gold & Silver Inc Common Shares (AYA)	2008-2010	136.36%

Mid-cap stocks are treated as having a market cap between $2B and $10B.