Impairment of vascularization of the surface covering epithelium induces ischemia and promotes malignization: a new hypothesis of a possible mechanism of cancer pathogenesis

Salivary Neutrophil-to-Lymphocyte Ratio as a Prognostic Predictor of Oral Premalignant and Malignant Disorders: A Prospective Study

INTRODUCTION

Inflammation is a definitive characteristic of carcinogenesis. The neutrophil-to-lymphocyte ratio (NLR) is an easy and efficient indicator of inflammation and a valuable marker in individuals with malignancies. The present study was performed to ascertain NLR values in salivary samples collected from individuals with oral premalignant disorders (OPMDs) and to assess the prognostic significance of NLR in distinguishing OPMDs from oral malignancies.

MATERIALS AND METHODS

This study was conducted on 50 patients histopathologically diagnosed with OPMDs with mild dysplasia. The patients were provided with standard medicinal treatment, encouraged to quit their habits, and followed up for one year at three-month regular intervals. During the follow-up, 29 (67.4%) patients completely recovered, whereas 14 (32.6%) developed oral malignancies. Salivary samples were collected at baseline (T0) and one-year follow-up (T1). The total salivary neutrophils and lymphocytes were counted using an improved cell counting method with a Neubauer chamber. The NLR values were calculated at T0 and T1. The paired t-test was used to compare the NLR values at T0 and T1. The cutoff value of the NLR was determined using the receiver operating characteristic (ROC) curve. The Youden index was used to determine the optimal cutoff NLR values in the groups. Statistical significance was set at p ≤0.05.

RESULTS

OPMDs were predominantly observed in males, with leukoplakia being the most prevailing one. Erythroplakia exhibited the highest propensity for malignant transformation, and habitual consumption of alcohol and tobacco was identified as a risk factor for this transformation. NLR increased in both premalignant and malignant conditions. NLR value equal to or exceeding 4 was determined to be a reliable indicator for the occurrence of oral cancer in patients with OPMDs. The ROC curve analysis yielded a sensitivity and specificity of 92%, with an area under the curve (AUC) of 0.928.

CONCLUSION

The poor prognosis of oral cancers was associated with higher NLR values. NLR values in salivary samples can serve as an independent reliable predictor in oral cancer and OPMDs.

Intraepithelial ischemia is a principal factor promoting cancerization of the covering epithelial tissues

Prominent angiogenesis, which is a hallmark of invasive cancer is preceded at the precancerous stage by marked ischemia. Our hypothesis proposes a structural mechanism responsible for altering blood flow in the covering epithelium and leading to marked reduction of vascularization in the foci of dysplasia. This mechanism varies from one type of epithelium to another. In squamous epithelium only basal cells are in direct contact with stromal vessels. To supply nutrients to the rest of the cells located at different levels, the subjacent stroma forms excrescences which penetrate upward together with blood capillaries. As soon as precancerous dysplastic alterations start and progress the number of intraepithelial blood vessels simultaneously decreases, thus leading to ischemia which precedes or promotes malignization of the covering squamous epithelium. To compensate for the deficit in blood supply, the dysplastic cells penetrate deeper into the underlying stroma, commencing invasion. Thus, the cells destroy the subjacent stroma not because they are initially "malignant", but due to ischemia which provokes the search for nutrients. Comparing squamous epithelium with glandular respiratory epithelium shows that the latter contains no blood capillaries at all. However, unlike squamous epithelial coverings, in respiratory epithelial covering, each cell is attached directly to the basal membrane and has ample access to the blood supply. Covering respiratory epithelium itself seldom gives rise directly to malignant growth. Cancerization of this type of epithelium occurs in the foci of squamous metaplasia. The latter are not supplied by a sufficient amount of blood vessels and in the majority of cases remain fragile and vulnerable structures, easily prone to malignization. Further study of these phenomenon should include the clarification of the influence of carcinogenic agents on the mechanism of adequate vascularization at the precancerous stage.