Par Pacific (PARR) had the highest return between 2010 and 2013 by a mid-cap US stock, returning 3,616.7%.

ASSET	YEARS	% RETURN
Par Pacific (PARR)	2010-2013	3,616.67%
Aurinia Pharmaceuticals (AUPH)	2010-2013	1,937.36%
ACADIA Pharmaceuticals (ACAD)	2010-2013	1,793.18%
Nexstar Broadcasting (NXST)	2010-2013	1,301.9%
Vipshop (VIPS)	2010-2013	1,294.7%
Patrick Industries (PATK)	2010-2013	1,075.97%
Melco Resorts & Entertainment (MLCO)	2010-2013	1,030.27%
Acadia Healthcare (ACHC)	2010-2013	956.47%
Astronics (ATRO)	2010-2013	925.68%
Almonty Industries Inc Common Shares (ALM)	2010-2013	849.8%
Lithia Motors (LAD)	2010-2013	785.39%
Bausch Health Companies (BHC)	2010-2013	785.27%
DXP Enterprises (DXPE)	2010-2013	768.78%
Axos Financial (AX)	2010-2013	684.3%
CVR Energy (CVI)	2010-2013	682.12%
Travere Therapeutics (TVTX)	2010-2013	677.78%
Dorman Products (DORM)	2010-2013	637.24%
Polaris Industries (PII)	2010-2013	617.59%
Himax Technologies (HIMX)	2010-2013	582.15%
PDF Solutions (PDFS)	2010-2013	543.72%
Under Armour Inc A (UAA)	2010-2013	535.6%
Boyd Group Services (BGSI)	2010-2013	515.64%
Western Alliance Bancorporation (WAL)	2010-2013	513.37%
PriceSmart (PSMT)	2010-2013	491.37%
Sirius XM (SIRI)	2010-2013	482.64%

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