However, this trend is sometimes reversed in thymoma: ALDH1A1, ALDH1B1, ALDH3A2, ALDH5A1, ALDH6A1, ALDH7A1, ALDH9A1, and ALDH18A1 expression is higher in thymoma than in corresponding paracancerous tissues. Here, ALDH18A1 is linked to thymoma.