Classe M, Burgess A, El Zein S, et al. - A retrospective study was done on a bicentric series of 45 cases in order to investigate the prognostic potential of the Ki67 proliferation index (PI) and tumor-infiltrating lymphocytes (TILs) in olfactory neuroblastomas (ONBs, rare malignant tumors that arise in the nasal vault). Hyams grades I, II, III, and IV estimated for 13.4%, 44.4%, 20% and 22.2% of all cases, respectively in this series. The Ki67 PI varied from 1 to 93 and in Hyams grade III-IV ONBs vs Hyams grade I–II ONBs, the Ki67 PI was considerably higher. A Ki67 PI of ≥ 25 was related to poorer survival. In both stromal and intratumoral compartments, TILs were present, although, they were located mostly in the stromal part of the tumor. In high-grade ONBs vs low-grade ONBs, the numbers of intratumoral CD8+ cells/mm² and CD4+ cells/mm² were greater. The numbers of T cells/mm² and B cells/mm² were not correlated with survival, however, a CD4/CD8 ratio of > 2 was significantly related to shorter survival. Hence, it was found through the findings that the Ki67 PI and TILs could be employed as prognostic markers and as a possible option to the Hyams grade.