How to obtain a numerical expressión in Traditional Form without making calculus?

How to obtain a expression without making the final calculation?

TraditionalForm(2*3^3 + 5^2)

I´d like to obtain 2*3^3 + 5^2 shoed in Traditional Form
I don´t like to obtain 79

Addon after bobthechemist’s answer

How to obtain that from a String (The expression is stored in a String )

a = "2*3^3+5^2"