CCND1 and squamous cell carcinoma: However, according to previous studies, the role of Cyclin D1 as a prognostic marker remains controversial [32], [33], [34], [35], [36], [37] and there is no consensus on the use of Bcl-2 as a prognostic marker [38], [39], [40], [41] for squamous cell carcinomas among head and neck cancer patients either.