Myb Immunohistochemical Staining and Fluorescence in situ Hybridization in Salivary Rare Basaloid Lesions.

Objective: Salivary rare basaloid lesions, including cribriform type basal cell adenoma (cBCA), BCA with incomplete capsule (iBCA), sialoblastoma (SB), and intercalated duct hyperplasia (IDH), could easily be misdiagnosed as adenoid cystic carcinoma (AdCC). We aim to identify an approach for differential diagnosis and to establish an optimal workflow concerning the diagnosis of these lesions. Material and methods: A panel of antibodies (MYB, β-catenin, CD117, SOX10, ki67, P63, calponin) and fluorescence in situ hybridization (FISH)-MYB were utilized to distinguish above salivary basaloid diseases from AdCC. Results: Histologically, the striking diagnostic features of cBCA, iBCA, SB, and IDH are composed of basaloid tumor cells, well-defined encapsulation, or lack of destructive invasion. Immunohistochemically, Myb immune-labeling could effectively make a distinction among cBCA, iBCA, SB, and IDH from AdCC, except in SB. cBCA and iBCA typically expressed β-catenin in the nuclei of tumor cells. There was no statistical significance in the ki67 index between SB and AdCC, but their indices were significantly higher than those of iBCA and IDH (p < 0.05, p < 0.05, respectively). P63 and calponin immune-expression were observed in the basaloid or myoepithelial cells. CD117 were observed positively in cBCA, iBCA, SB, and AdCC, except in IDH. SOX10 were observed positively in all cases. No cases had fusion of MYB and NFIB detectable by FISH, except in AdCC. Conclusion: Considering their sensitivity and specificity, FISH-Myb and an immunohistochemical panel of MYB/β-catenin/ki67 would be an optimal choice for the differential diagnosis of these basaloid lesions. Clinical relevance: Some salivary basaloid tumor or tumor-like lesions have overlapping features with AdCC. Through this present research, we suggested that the panel IHC of MYB, βcatenin, and ki67 combined with FISH-Myb should be an optimal choice for differential diagnosis among those lesions.