Previous studies have suggested that cyclin D2 expression is related to poor prognosis in CRC patients [27], and an increase in cyclin D2 levels resulting in overproliferation was reported in various premalignant [40,41,42] and cancer tissues [24], including germ cell tumors [43], hematopoietic cells [21,25,44,45], granulosa cells [22,46], gastric tumors [47,48], and CRC [49]. Here, CCND2 is linked to testicular germ cell tumor.