High histamine expression by early-stage squamous cell carcinoma of the tongue is associated with a poor prognosis.

Background: Although not widely known, several types of cancers express histamine. Squamous cell carcinoma (SCC) of the tongue is one such cancer, and histamine expression is associated with the tumor microenvironment. Our aim was to examine whether histamine expression is a useful prognostic factor for tongue SCC.

Methods: Histamine cannot be accurately measured directly because it is rapidly degraded after secretion. Therefore, L-histidine decarboxylase (HDC), an enzyme that synthesizes histamine in a single step, was used to estimate histamine secretion. In a retrospective study, tongue SCC samples from patients were immunohistochemically stained for HDC; the staining intensity was semi-quantified and evaluated relative to indices used in histopathological diagnosis.

Results: High expression of HDC was associated with the worst tumor invasion and tumor budding. Overall survival curves revealed that patients with tongue SCC showing high HDC expression had a poor prognosis.

Conclusions: The expression of histamine may be a prognostic indicator for tongue SCC.