ACADIA Pharmaceuticals (ACAD) had the highest return between 2012 and 2016 by a mid-cap US stock, returning 2,521.8%.

ASSET	YEARS	% RETURN
ACADIA Pharmaceuticals (ACAD)	2012-2016	2,521.82%
Par Pacific (PARR)	2012-2016	2,323.33%
Patrick Industries (PATK)	2012-2016	1,747.45%
Vipshop (VIPS)	2012-2016	1,734.99%
CleanSpark (CLSK)	2012-2016	1,246.17%
Cidara Therapeutics (CDTX)	2012-2016	1,200%
IES (IESC)	2012-2016	949.32%
DXC Technology (DXC)	2012-2016	928.17%
Travere Therapeutics (TVTX)	2012-2016	896.32%
Addus HomeCare (ADUS)	2012-2016	879.05%
American Airlines (AAL)	2012-2016	820.36%
Caesars Entertainment (CZR)	2012-2016	801.6%
Repligen (RGEN)	2012-2016	790.75%
Nexstar Broadcasting (NXST)	2012-2016	749.57%
Ligand Pharmaceuticals (LGND)	2012-2016	746.75%
Ambarella (AMBA)	2012-2016	706.71%
Western Alliance Bancorporation (WAL)	2012-2016	668.3%
Radian (RDN)	2012-2016	663.28%
TAL Education (TAL)	2012-2016	641.97%
Axos Financial (AX)	2012-2016	601.47%
Sarepta Therapeutics (SRPT)	2012-2016	505.52%
HCI (HCI)	2012-2016	493.83%
JBTMarel (JBTM)	2012-2016	477.5%
Mueller Water Products (MWA)	2012-2016	470%
Trex (TREX)	2012-2016	450.43%

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