Ki-67 is a powerful tool for grading neuroendocrine tumors among Egyptian patients: a 10-year experience.

Background: Neuroendocrine tumors (NETs) arise in most organs of the body and share many common pathologic features. However, a variety of organ-specific systems have been developed for nomenclature, grading and staging of NETs, causing much confusion. In collaboration with WHO, the European Neuroendocrine Tumor Society (ENETS) recommended the use of either mitotic rate or Ki-67 labeling index (LI) for grading and classification. We aim to explore the profile of NETs in Egyptian patients and apply the ENETS system.

Materials And Methods: This retrospective study was carried out on all cases of NETs diagnosed at the Pathology Department, National Cancer Institute, Cairo University, during the period from January 2000 to December 2009. Data about age, sex, anatomic site of tumor, tumor size, tumor stage and presence of nodal metastasis were retrieved. Ki-67 immunostaining and grading according to ENETS were done.

Results: There was a trend toward increased mean age and tumor size and grade according to Ki-67, with significant statistical difference (p < 0.001 and 0.036, respectively). Estimation of mitotic count and Ki-67 LI was strongly associated with NET histopathologic types, but this association was stronger regarding Ki-67 LI than mitotic count (p = 0.002 and 0.035, respectively). On the other hand, there was discordance between grading according to mitotic count and grading according to Ki-67 LI in relation to NET histopathologic subtypes. Concordance between mitotic rate and Ki-67 LI was reported in 18.89% of cases, while discordance occurred in 81.11% of cases and was more prevalent in G3.

Conclusion: Ki-67 is a reliable and reproducible marker for grading of NETs and more superior than mitotic rate.