Sandstorm Gold Ltd N (SAND) had the highest return in the 2010s by a mid-cap US stock, returning 796,044.4%.

ASSET	DECADE	% RETURN
Sandstorm Gold Ltd N (SAND)	2010s	796,044.44%
Freedom (FRHC)	2010s	765,163.16%
Inventrust Properties (IVT)	2010s	626,410%
Weatherford International (WFRD)	2010s	219,277.6%
Caesars Entertainment (CZR)	2010s	4,487.69%
Novanta (NOVT)	2010s	3,368.24%
Nexstar Broadcasting (NXST)	2010s	3,182.2%
ACADIA Pharmaceuticals (ACAD)	2010s	3,140.91%
MarketAxess (MKTX)	2010s	3,013.13%
Vipshop (VIPS)	2010s	2,261.64%
Repligen (RGEN)	2010s	2,118.23%
TAL Education (TAL)	2010s	2,095.9%
Patrick Industries (PATK)	2010s	2,041.52%
Lithia Motors (LAD)	2010s	1,890.36%
Jazz Pharmaceuticals (JAZZ)	2010s	1,752.11%
Trex (TREX)	2010s	1,716.64%
Silicon Motion Technology (SIMO)	2010s	1,695.92%
Sapiens International (SPNS)	2010s	1,638.67%
Universal Display (OLED)	2010s	1,548.41%
Travere Therapeutics (TVTX)	2010s	1,477.78%
Align Technology (ALGN)	2010s	1,445.93%
EPAM Systems (EPAM)	2010s	1,442.98%
Western Alliance Bancorporation (WAL)	2010s	1,381.17%
Match (MTCH)	2010s	1,364.5%
Sarepta Therapeutics (SRPT)	2010s	1,353.15%

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