Role of Ki-67 in the Grading of Mucoepidermoid Carcinomas

Abstract

Background: To determine the expression of Ki-67 in mucoepidermoid carcinoma (MEC) and to correlate with histological grades.
Methods: In this descriptive study, histopathological grading of mucoepidermoid carcinomas was done on the basis of grading system of Auclair et al. Points were assigned on the basis of five histopathological features( intracystic component, neural invasion, necrosis, mitosis and anaplasia).
After grading of the tumor , immunohistochemical marker Ki-67 was applied. For Ki-67 expression, the scoring system of Lyzogubov et al was followed . The chi-square test was used to compare histological grade with expression of immune marker Ki-67. P value < 0.001 was considered statistically significant.
Results: Out of 30 cases, majority( 70%) were males, with male to female ratio of 1:0.43.The range in age of the patient was 17 to 88 years and mean age was 44.27 years. Parotid gland was the most common site. Thirteen (43%) were low grade cases, 10 (33%) were high grade cases and 7 (23%) were intermediate grade cases of MEC. The Ki-67 % expression in low grade MEC varied between 0-10% with mean expression of 2.85%. While the expression in intermediate grade was 5-40% with a mean of 25% and the Ki-67 % expression in high grade was 30-75% with a mean of 61.5%.This highlighted increasing Ki-67 expression with worsening grade of the tumour.
Conclusions: Expression of Ki-67 is high in high grade cases of MEC while it is negative or less positive in low grade cases of MEC. Correlation between grades of MEC and expression of Ki-67 is statistically significant. It can be used as a prognostic marker for MEC along with other prognostic and clinicopathological parameters.