Lantheus (LNTH) had the highest return in August 2016 by a mid-cap US stock, returning 131.1%.

ASSET	MONTH	% RETURN
Lantheus (LNTH)	August 2016	131.07%
Comstock Resources (CRK)	August 2016	77.06%
Genworth Financial (GNW)	August 2016	61.99%
Madrigal Pharmaceuticals (MDGL)	August 2016	57.01%
Weibo (WB)	August 2016	46.58%
Ocular Therapeutix (OCUL)	August 2016	45.56%
Amkor Technology (AMKR)	August 2016	44.91%
Chemours (CC)	August 2016	42.2%
SM Energy (SM)	August 2016	40.51%
Catalyst Pharmaceuticals (CPRX)	August 2016	39.43%
Grupo Simec SAB de CV ADR (SIM)	August 2016	37.44%
Applied Digital (APLD)	August 2016	37.25%
PTC Therapeutics (PTCT)	August 2016	36.15%
Nomad Foods (NOMD)	August 2016	32.69%
Globalstar, Inc Common Stock (GSAT)	August 2016	32.2%
Bausch Health Companies (BHC)	August 2016	31.83%
PennyMac Finl Svcs (PFSI)	August 2016	31.14%
Workiva (WK)	August 2016	28.3%
Archrock (AROC)	August 2016	27.66%
Etsy (ETSY)	August 2016	27.58%
Civitas Resources (CIVI)	August 2016	27.5%
Addus HomeCare (ADUS)	August 2016	27.49%
Trex (TREX)	August 2016	27.42%
Skyline (SKY)	August 2016	26.99%
Axos Financial (AX)	August 2016	26.84%

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