Tissue eosinophilia in oral intraepithelial neoplasia as a probable indicator of invasion

Objective: To investigate the presence of eosinophils in oral intraepithelial neoplasia (OIN) and oral squamous cell carcinoma (OSCC) lesions and its relation to invasion. Subjects and methods: Ninety-nine oral biopsies were selected and subdivided into the following: OIN-1(16 cases), OIN-2 (18 cases), OIN-3 (17 cases), microinvasive OSCC (10 cases), non-metastatic OSCC (22 cases) and metastatic OSCC (16 cases). The tissue eosinophilia was evaluated histologically in slices stained with haematoxylin and eosin. Results: Eosinophil distribution was associated with diagnosis severity (p <.01). A significant difference was found between OIN-3 or microinvasive OSCC and non-metastatic or metastatic OSCC. Stromal invasion threshold was 7 eos/10 high power field (hpf) (96.1% specificity and 62.5% sensitivity). Eosinophils were absent in OIN-1; in OIN-2, two cases were positive. In OIN-3, five cases showed tissue eosinophilia, four of which had ≥3 eos/hpf or ≥7 eos/10 hpf. Three cases were suspected of invasion; two had a previous history of OSCC with elevated eosinophil infiltrate. In microinvasive OSCC, the four positive cases presented ≥3 eos/hpf and ≥7 eos/10 hpf. Although not significantly different, non-metastatic invasive OSCC had a higher number of cases (68.2%) with ≥22 eos/10 hpf contrasting with 50% in metastatic OSCC. Conclusion: Our results suggest that eosinophils can be considered an indicator of invasion in OIN, helping in cases of difficult diagnosis.