That really depends. If you build your application on Node, you don't need Tomcat, but Node is certainly not a drop-in replacement for Tomcat. 

Node and Tomcat are two very different things. Tomcat is a server for Java applications with a lot of built-in features and extras that are available with no add-ons. 

Node is a server-side JavaScript environment that powers JavaScript applications. It is not a server, but you can build servers in Node with a few lines of code. 

Node features: 

  1. A fast JavaScript engine (built on V8). 
  2. Asynchronous by default philosophy (nothing should block). 
  3. Event-loop design (much like the browser environment). 
  4. Networking as a first class citizen (create production capable servers with few lines of code). 
  5. A highly usable streams API. 
  6. A large, rapidly growing developer community. 
  7. A simple, CommonJS-based module solution that guarantees module encapsulation (your var declarations are limited to module scope). 
  8. A developer friendly package management system with thousands of open-source packages to choose 
  9. from.