(“In … terms” structure) What should be in the blank space?
Answer: an adjective, modifying "terms".
In English, you can use nouns as adjectives, so a noun is also possible. However, as mentioned in the comments, "In {noun} terms is a fairly casual, conversational pattern". The proper choice would be an adjective.
The question was also answered on this stackexchange post in the same way, as follows.
The general forms are either:
- In terms of [Noun]
- In [Adjective] terms.
Next, you asked about specific sentences:
A: In histology terms
B: In business terms
For these sentences, using a noun in that position appears to be a fairly casual, conversational pattern, and not formally correct.
What kind of noun would you prefer?
Nouns are not preferred. However, to proceed and answer the question anyway, the word should be the appropriate one for the situation, and that applies to language in general, not only to the phrase "in [__] terms". For example,
What kind of noun would you prefer in the phrase "The fast ___"?
"The fast car" would make sense. "The fast pillow" would usually not make sense. So, "what kind of noun would you prefer?" - one that makes sense in the sentence.