"narrow topic" is a correct phrase that can be used in written English.
For example, "I chose to focus on a narrow topic for my research paper, the history of the potato."
This book, the exhibition's catalog, gives its narrow topic a surprisingly interesting, well, spin.
Most are dedicated to a special interest, which may be an extremely narrow topic.
Lead author Johan J Mattelaer brings a broad perspective to this narrow topic.
In the College Scholar program, students have the flexibility to integrate related disciplines from a broader perspective or to focus on a narrow topic in an interdisciplinary field.
Luckily, the filmmaker Gary Hustwit — who was an executive producer of the mesmerizing "Moog," about the analog synthesizer — has a knack for finding a universe within a narrow topic.
Second, I believe the editorial move in the direction of subject matter like this — college admissions is a very narrow topic area — may indicate that news judgment is changing.
In some cases, donors have requested scholarly attention to relatively narrow topics.
Compiler research for a long time was moribund, stuck on narrow topics such as register allocation and instruction scheduling.
I think the new mayor will not limit his conversation to narrow topics and that kind of attitude will hold him in good stead around here".
"I try to narrow topics down to a simple drawing so they can understand and visualize what scientists are doing inside the lab," she says.
However, it was also a reflection of the fact that such an adventurous approach ran counter to an academic tradition that placed greater value on the massive accumulation of empirical data about relatively narrow topics than on interpretative boldness or methodological novelty.
