Tokyo stocks were mostly flat Monday morning, as gains from semiconductor-related shares offset selling amid caution before a slew of major Japanese companies release their earnings results. The 225-issue Nikkei Stock Average rose 14.48 points, or 0.04 percent, from Friday to 38,243.59. The broader Topix index was down 0.18 point, or 0.01 percent, at 2,728.03. The U.S. dollar remained firm in the upper 155 yen range in Tokyo, as traders bought the currency on prospects of a wider interest rate differential between Japan and the United States after long-term Treasury yields rose last week. At n…