Histochemical analysis of mucin expression using mucicarmine and periodic acid-Schiff stains in pleomorphic adenoma and mucoepidermoid carcinoma: An unexplored niche in salivary gland tumour pathology.

Background: Salivary glands, as exocrine glands, play a crucial role in saliva production, vital for maintaining oral cavity health and moisture. Histochemical analysis of saliva identifies mucins as its primary component. Variations in mucin characteristics could potentially indicate early neoplastic changes. Utilizing special stains such as PAS and mucicarmine is essential for accurately diagnosing salivary gland neoplasms (SGNs). This study focuses on the histochemical analysis of pleomorphic adenoma (PA) and mucoepidermoid carcinoma (MEC) to evaluate mucin expression using periodic acid-Schiff (PAS) and mucicarmine stains. Aim: To access, analyse and compare the mucin expression in cases of PA and MEC. Materials and Methods: The study group comprised 41 SGNs, which included 21 cases of MEC and 20 cases of PA, and 15 cases of normal oral mucosa containing minor salivary gland tissues were included in the control group. Histopathologically diagnosed cases, both PA and MEC, were selected, and tissue sections were stained with PAS and Mucicarmine to assess and analyse the mucin expression. Pearson's Chi-squared test was applied for the statistical analysis. Results and Conclusion: MEC stained with mucicarmine and PAS showed strong mucin expression in low-grade cases, moderate expression in intermediate-grade cases and weak mucin expression in high-grade cases, showing a statistically significant difference (P < 0.05). PA cases were similarly stained with mucicarmine and PAS, and it was found to have strong mucin expression in the cellular variant, moderate expression in the mixed variant and weak mucin expression was observed in the myxoid variant, giving us a statistically significant result (P < 0.05). Therefore, it was concluded that mucin expression decreased with increasing grades of MEC, but mucin expression increased proportionally with the cellularity of PA.