Immunohistochemical analysis of phospho-ERK1/2 in odontogenic cysts

To evaluate the expression levels, cellular localization, and clinicopathological associations of p-ERK1/2 in dentigerous cysts (DCs), odontogenic keratocysts (OKCs), and calcifying odontogenic cysts (COCs).

Immunohistochemistry was performed on 80 formalin-fixed paraffin-embedded tissue samples (16 DCs, 40 OKCs, and 24 COCs). The immunolocalization and expression levels of p-ERK1/2, a key downstream effector of the MAPK/ERK pathway, were semi-quantitatively evaluated and compared across cyst types. Associations between p-ERK1/2 expression and the clinicopathological characteristics of each lesion were also statistically analyzed.

p-ERK1/2 was predominantly localized in the cytoplasm and/or nucleus of epithelial lining cells of OKCs. Most DCs (68.8%, p=0.006) and COCs (79.2%, p<0.001) showed significantly negative p-ERK1/2 immunostaining. In contrast, the majority of OKCs (75%) exhibited p-ERK1/2 expression. The median immunoreactive score of OKCs (5.49 (1.84-7.84)) was significantly higher than the scores for DCs (p=0.004) and COCs (p<0.001). No significant association was observed between p-ERK1/2 expression and any clinicopathological parameters in the DC and OKC groups. However, p-ERK1/2 expression in COCs was significantly associated with sex (p=0.047).

Elevated p-ERK1/2 expression in OKCs indicates that MAPK/ERK pathway activation may be specifically involved in OKC pathogenesis compared with DCs and COCs. However, the clinicopathological significance of p-ERK1/2 appears to be restricted to selected clinicopathological features in COCs.