The development of a Raman spectroscopy-based workflow for the identification of salivary gland tumor tissue and the discussion of the barriers of translation of spectroscopic methods

The pre-, intra- and postoperative determination of the entity and dignity of salivary gland tumors (ST) based solely on histomorphological criteria is not reliably in all cases. The spectra of Raman spectroscopy (RS) contain information about the molecular composition of the examined tissue. The aim of the work was to establish an RS-based measurement setup and a workflow for the differentiation of salivary gland tumor tissue and salivary gland tissue. In addition, the barriers of translating RS in salivary gland diagnostics are discussed. 10 µm thick, native cryo-tissue sections of Warthin tumors (n=5) and pleomorphic adenomas (n=4) were examined using RS in both tumor tissue and healthy salivary gland tissue and the data were evaluated in a multivariate data analysis. All measurements were histomorphologically localized in a corresponding HE section. A "principal component" analysis (PCA) of the RS data and coupled discriminant analysis enabled both a distinction between tumor and non-tumor tissue as well as the differentiation of the various tumor entities (based on the histopathological assessment) with a high level of accuracy (93% ). In summary, it could be shown that the RS measurements could be used to reliably distinguish between ST and healthy salivary gland tissue. Another important result is that tissue processing is possible reliably using standard pathological methods. The high number of different ST entities represents a biostatistical challenge. Approaches to the solution include multi-level statistical models and simultaneous correlation with histomorphological criteria.