Freedom (FRHC) had the highest return between 2016 and 2017 by a mid-cap US stock, returning 4,140%.

ASSET	YEARS	% RETURN
Freedom (FRHC)	2016-2017	4,140%
Riot Blockchain (RIOT)	2016-2017	1,226.92%
Chemours (CC)	2016-2017	877.05%
Madrigal Pharmaceuticals (MDGL)	2016-2017	694.72%
Lantheus (LNTH)	2016-2017	519.7%
EXACT Sciences (EXAS)	2016-2017	485.08%
Light & Wonder (LNW)	2016-2017	484.95%
Weibo (WB)	2016-2017	452.08%
NexGen Energy (NXE)	2016-2017	402.95%
Huazhu (HTHT)	2016-2017	376.51%
Burford Capital (BUR)	2016-2017	370.93%
Cleveland-Cliffs (CLF)	2016-2017	359.23%
United States Steel (X)	2016-2017	357.88%
Leonardo DRS, Inc Common Stock (DRS)	2016-2017	305.26%
Alpha Metallurgical Resources (AMR)	2016-2017	300.58%
IAMGold (IAG)	2016-2017	299.32%
Casella Waste Systems (CWST)	2016-2017	290.17%
TAL Education (TAL)	2016-2017	289.69%
Skyline (SKY)	2016-2017	275.72%
Cognex (CGNX)	2016-2017	273.82%
Novanta (NOVT)	2016-2017	273.41%
Corcept Therapeutics (CORT)	2016-2017	272.37%
Transportadora de Gas del Sur SA ADR (TGS)	2016-2017	268.55%
SPX (SPXC)	2016-2017	240.46%
Pampa Energia SA ADR (PAM)	2016-2017	232.25%

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