Significance of neo-angiogenesis and immuno-surveillance cells in squamous cell carcinoma of the tongue

BACKGROUND: Neo-angiogenesis is an essential process in physiological and pathological conditions. However, it is a complex process. Several studies demonstrated that intra-tumoural microvessel number is a significant predictor of metastasis and clinical outcome in many tumours, including oral malignancies. The immuno-surveillance cells, mast cells and eosinophils are implicated in the biological behaviour of tumours. Nevertheless, their function in tissues is uncertain. Mast cells are involved in homeostatic regulation of blood vessels as well as host defence. In some malignancies, high mast cell density has been found to correlate with favourable prognosis. However, others reported unfavourable associations. Tumour associated tissue eosinophilia is a well-known phenomena. It has been associated with good and poor prognosis. However, the role of eosinophils in tumours remains controversial. Therefore, this study was designed to investigate the prognostic value of microvessel, mast cell and eosinophil densities in the context of clinico-pathological parameters and survival in squamous cell carcinoma of the tongue. MATERIALS AND METHODS: Anti-CD105 and anti-tryptase monoclonal antibodies were utilized to highlight and count microvessels and mast cells respectively in 81 cases of tongue squamous cell carcinoma. Eosinophils were demonstrated using carbol chromotrope histochemical stain. The densities were counted per mm2 and correlated with patients’ outcome and other clinico-pathological parameters using non-parametric tests and student's t-test. Clinically, the cases were divided into 4 main groups depending on survival time, lymph-node or distant metastasis. RESULTS: The 5 year survival was significantly lower in patients with a low mast cell density than those with a high density (p=0.006, Kruskal-Wallis test). The survival group-A demonstrated significantly higher mast cell and microvessel numbers than group-D (p=0.007, student's t-test) respectively. Patients with well- differentiated squamous cell carcinoma had significantly higher numbers of mast cells when compared to patients with poorly differentiated squamous cell carcinoma (p<0.05, student's t-test). The lymph node involvement correlation between the survival group-A and survival group-D was also significant (p=0.001, Mann-Whitney U test). CONCLUSION: Data from this study indicates that accumulating mast cells in tumours play a part in inhibiting tumour progression and is potentially angiogenic in tumours.