The top after-market NYSE gainers Monday were Greenway Medical Technologies, Harmony Gold Mining, Sturm, Ruger & Co, Health Net and ADT Corp. The top after-market NYSE losers were MBIA, Northern Tier Energy, Masco Corp and Newmont Mining Corp.

Gainers

Greenway Medical Technologies Inc. (NYSE:GWAY) shares climbed 5.08 percent to $13.01 in post-market trading. The stock tumbled more than 22 percent in regular trading after the company lowered its fiscal 2013 earnings outlook.

Harmony Gold Mining Co Ltd. (NYSE:HMY) shares gained 1.63 percent to $4.98 in post-market trading. The stock has a 52-week low of $4.57, a 52-week high of $10.73 and $2.13 billion in market capitalization.

Sturm, Ruger & Co. (NYSE:RGR) shares advanced 1.63 percent to $51.80 in post-market trading. Its first quarter net profit surged to $23.7 million or $1.20 per share from $15.5 million or $0.79 per share in the same period last year.

Health Net Inc. (NYSE:HNT) shares rose 1.55 percent to $29.91 in post-market trading. The company swung to first quarter net profit of $50.05 million or $0.62 per share compared to a net loss of $26.6 million or $0.32 per share in the same period last year.

ADT Corp. (NYSE:ADT) shares gained 1.44 percent to $44.27 in post-market trading. The stock has a 52-week low of $34.68, a 52-week high of $50.37 and $10.13 billion in market capitalization.

Losers

MBIA Inc. (NYSE:MBI) shares tumbled 5.48 percent to $9.31 in post-market trading. The stock has a 52-week low of $6.78, a 52-week high of $13.70 and $1.90 billion in market capitalization.

Northern Tier Energy L.P. (NYSE:NTI) shares plunged 2.38 percent to $25.42 in post-market trading. The stock has a 52-week low of $13.00, a 52-week high of $33.24 and $2.87 billion in market capitalization.

Masco Corp. (NYSE:MAS) shares declined 2.01 percent to $20.01 in post-market trading. The company reported adjusted net profit of $0.13 per share, up from $0.05 per share in the same period last year but fell short of analysts’ estimate of $0.14 per share.

Newmont Mining Corp. (NYSE:NEM) shares declined 1.97 percent to $33.30 in post-market trading. The company reported first quarter adjusted net profit of $354 million or $0.71 per share, down from $578 million or $1.15 per share in the same period last year and fell short of Reuters' estimate of $0.77 per share.

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