Expression of Fascin and SALL4 in odontogenic cysts and tumors: an immunohistochemical appraisal. [version 2; peer review: 2 approved with reservations, 1 not approved]

Background: Various stemness markers (SOX2, OCT4, and NANOG) have been studied in odontogenic cysts and tumors. However, studies on SALL4 having similar properties of stemness has not been documented. Additionally, insight into fascin as a migratory molecule is less explored. Following a thorough literature search we hypothesize that fascin might contribute for the local migratory behaviour of the odontogenic epithelial cells in tumors and cysts while SALL4 may contribute to stemness property. Thus, the aim of the present study was to evaluate the expression of fascin and SALL4 in histopathological variants of Ameloblastoma, Adenomatoid Odontogenic Tumor (AOT) and various odontogenic cysts namely Odontogenic keratocyst (OKC), Dentigerous cyst (DC), Radicular cyst (RC), and Calcifying odontogenic cyst (COC). Methods: Semi-quantitative analysis of fascin and SALL4 immuno-positive cells was evaluated in a total of 40 cases of ameloblastoma (11 plexiform, 12 follicular, 12 unicystic, and 5 desmoplastic) variants, 6 cases of AOT, 15 cases each of OKC, DC, RC and 5 of COC. Chi-square test was applied to evaluate the association between SALL4 and fascin expression in odontogenic cysts and tumors. Results: Fascin immunopositivity was observed in peripheral ameloblast-like cells, and the expression was weak or absent in stellate reticulum-like cells. A moderate to weak immune-reactivity to SALL4 was observed in the cytoplasm of ameloblastoma, epithelial cells of DC and RC having a marked inflammatory infiltrate, which was an interesting observation. COC and AOT had negative to weak expressions. Conclusion: Expression of fascin in ameloblastomas elucidate their role in motility and localized invasion. Its expression in less aggressive lesions like DC, COC, AOT will incite to explore the other functional properties of fascin. SALL4 expression in the cytoplasm of odontogenic cysts and tumors may represent inactive or mutant forms which requires further validation.