Tokyo stocks opened slightly lower Monday, as investors refrained from active buying ahead of upcoming earnings reports from major Japanese companies this week. In the first 15 minutes of trading, the 225-issue Nikkei Stock Average fell 72.92 points, or 0.19 percent, from Friday to 38,156.19. The broader Topix index was down 8.67 points, or 0.32 percent, at 2,719.54. On the top-tier Prime Market, decliners were led by real estate, nonferrous metal, and food shares. At 9 a.m., the U.S. dollar fetched 155.83-84 yen compared with 155.74-84 yen in New York and 155.68-70 yen in Tokyo at 5 p.m. Frid…