TG Therapeutics (TGTX) had the highest return in March 2017 by a mid-cap US stock, returning 104.4%.

ASSET	MONTH	% RETURN
TG Therapeutics (TGTX)	March 2017	104.39%
Power Solutions International, Inc Common Stock (PSIX)	March 2017	83.45%
Catalyst Pharmaceuticals (CPRX)	March 2017	75.68%
HUTCHMED DRC (HCM)	March 2017	53.46%
RH (RH)	March 2017	50.1%
National Beverage (FIZZ)	March 2017	43.76%
CleanSpark (CLSK)	March 2017	40.85%
Mesoblast (MESO)	March 2017	34.84%
Penn National Gaming (PENN)	March 2017	31.59%
Riot Blockchain (RIOT)	March 2017	29.87%
Plug Power (PLUG)	March 2017	26.61%
Star Bulk Carriers (SBLK)	March 2017	24.79%
New Oriental Education & Technology (EDU)	March 2017	23.35%
TAL Education (TAL)	March 2017	23.19%
SiteOne Landscape Supply (SITE)	March 2017	22%
Galapagos NV ADR (GLPG)	March 2017	21.46%
BRP (DOOO)	March 2017	21.06%
Corcept Therapeutics (CORT)	March 2017	20.84%
Cytokinetics (CYTK)	March 2017	20.09%
Supernus Pharmaceuticals (SUPN)	March 2017	19.92%
FMC (FMC)	March 2017	19.5%
Axcelis Technologies (ACLS)	March 2017	19.37%
Coca-Cola Consolidated (COKE)	March 2017	19.36%
Casella Waste Systems (CWST)	March 2017	19.17%
Transportadora de Gas del Sur SA ADR (TGS)	March 2017	18.7%

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