Activating Transcription Factor 1 (ATF1) Immunohistochemical Marker Distinguishes HCCC from MEC

Abstract

The study aimed to compare 15 cases of mucoepidermoid carcinoma (MEC) and 15 cases of hyalinizing clear cell carcinoma (HCCC) using immunohistochemical staining and molecular analysis. Thirty samples were examined, and markers, including p63, CK5/6, SOX10, CK7, ATF1, and FISH probes specific to EWSR1 and MAML2, were used. Clear cell differentiation was observed in all MEC cases to some extent, with clear cell MEC showing the most prominent findings. Clear cell features were also present in conventional MEC, oncocytic MEC, and Warthin-like MEC, although to a lesser extent. The majority of cases were classified as low-grade MECs. MAML2 rearrangement was detected in all cases (except cases 11 and 14), while EWSR1 rearrangement was observed in a single case of clear cell MEC. These findings helped identify distinct subtypes within the mucoepidermoid carcinoma spectrum. The study emphasized the importance of utilizing immunohistochemical profiles, histopathological features, and molecular analysis for accurate diagnosis and classification of salivary gland neoplasms. HCCC was also discussed, and ATF1 was proposed as a marker to distinguish HCCC from morphologically similar neoplasms. The study concluded that a comprehensive approach combining immunohistochemistry, histopathology, and clinical correlation is essential for accurate diagnosis and classification, considering the variable expression of markers and potential overlap with other tumor types.