What happened

Shares of American Tower (NYSE: AMT) rose 11.9% in March, according to data from S&P Global Market Intelligence. The operator of wireless networking sites, including 41,000 American and 130,000 international cell towers and small cell sites, sparked this surge with a mixed fourth-quarter report near the end of February.

So what

American Tower's fourth-quarter report showed revenues rising 25% year over year, stopping at $2.13 billion. Your average analyst would have settled for $2.03 billion. Earnings of $0.62 per share fell short of Wall Street's expectations for $0.77 per share, but the top-line surprise took priority over the bottom-line miss. Revenue surprises are not common for ultra-predictable businesses like American Tower, where the average client lease comes with a contract length of more than four years.

Analysts weighed in on American Towers' results over the next few days, often with bullish analyses. Another tailwind followed three weeks later, when the company refinanced $1.2 billion of long-term debt papers from a 5.05% annual interest rate to a gentler 3.375% APR.

A fully stacked cell tower in silhouette against a colorful sunrise.

Image source: Getty Images.

Now what

This company might look like it's stuck in a slow-moving, mature business. But those long-term contracts actually serve as a solid platform from which American Tower can launch ambitious growth strategies. At the moment, that includes rapid expansion overseas and plenty of tower-based equipment upgrades. In advanced markets like North America and Western Europe, we're looking at the upcoming 5G wireless standard; developing territories such as India and Latin America are rolling out 4G networks to replace their aging 2G and 3G hardware. Hence, American Tower reaps surprisingly quick growth results in a seemingly sedate industry.