What is a syntactic approach?
Heres the definition of syntax: syntax: Definition from Answers.com
For me, the word is used most often to refer to computer programming languages, where correct syntax is essential to working programs, but definition number 3 gives a more general use of it. "A systematic, orderly arrangement."
In your context, I would guess it simply means classifying different cells by their shape, and using this 'syntax' as an identification method (As opposed to any other identification methods there may be, using some chemical/physical process).
There are several books on the subject, but interest in this field seems to have faded considerably over time (which I believe is due to the difficulty of applying this technique).
Data Mining in MATLAB