As long as no confusion arises, foreign words can be cited as if they were Chinese words.
E.g. 胡安发现preoccupation这个词在中文里没有很好的翻译。
(或)胡安发现preoccupation在中文里没有很好的翻译。
(Juan found that (the word) "preoccupation" doesn't have a good translation in Chinese.)
E.g. 在西班牙语中,gustar的用法与tomar, correr等动词相比显得比较特别。
(In Spanish, the usage of "gustar" seems quite peculiar in comparison to that of the verbs "tomar", "correr", etc.)
Caveat: Be careful of the use of punctuation marks when citing foreign words in a Chinese context. E.g. 中文里没有单词能翻译英文单词fundamentalist. (The period after "fundamentalist" is in the English style, not in the Chinese style.)
P.S.: It is deprecated to directly cite foreign words in Chinese unless it is for linguistic pedagogic purposes.