CD44v6 expression in gastroenteropancreatic neuroendocrine neoplasms: Clinicopathological correlation and prognosis

Background: Clinical course of gastroenteropancreatic neuroendocrine neoplasm (GEP-NEN) patients are determined by complicated and multifaceted factors. Ki-67 has been used to predict the behavior of NEN with statistically significant high probability. Immunohistochemical prognostic markers other than Ki-67 have been reported, but due to insufficient validation, they have not been used routinely. CD44 and its isoform variants showed significant inverse correlation with lymph node status, distant metastasis, and mortality in pancreatic neuroendocrine neoplasm (Pan-NEN). The aim of this study is to determine the prognostic value of CD44v6 expression among GEP-NENs.

Materials and methods: Immunohistochemical staining (IHC) of CD44v6 was studied in 26 formalin-fixed-paraffin-embedded (FFPE) specimens from GEP-NENs patients in the Srinagarind Hospital, Khon Kaen University, Thailand, between 2013 and 2018. Demographic data were collected. IHC staining result was interpreted based on H-score and correlated with neuroendocrine IHC markers, proliferation index, lymph nodes status, metastasis, and patients' survival.

Results: All cases showed variable staining for CD44v6 without statistically significant correlation with age, gender, histological grading, lymph node metastasis, distant metastasis, Ki-67 proliferative index, or neuroendocrine marker expression. Survival analysis showed association of higher CD44v6 expression with better prognosis (p = 0.033). Hazard ratio of CD44v6 low expression patients with age ≥ 49 was 12.736 (p = 0.028, 1.318-123.073), presence of lymph node metastasis was 8.267 (p = 0.036, 1.142-59.841), presence of distant metastasis 12.736 (p = 0.028, 1.318-123.073).

Conclusion: Higher expression of CD44v6 IHC is significantly associated with better overall survival, histological grading, and Ki-67 index of GEP-NENs patients. CD44v6 IHC can be used as an additional prognostic immunohistochemical marker related to the metastatic status.