Raman spectroscopy discriminates malignant follicular lymphoma from benign follicular hyperplasia, from tumor metastasis, and is able to classify follicular lymphomas according to tumor grade and BCL2 protein expression

Raman spectroscopy is a non-destructive label-free technique providing biochemical tissue fingerprint. Theobjective of the present work was to test if Raman spectroscopy is a suitable tool to differentiate lymph nodesaffected by different conditions, such as reactive follicular hyperplasia (benign), follicular lymphoma (low gradeprimary tumour), diffuse large B cell lymphoma (high grade primary tumour) and tumour metastasis (secondarytumours). Moreover, we tested its ability to discriminate follicular lymphomas by the tumour grade and theBCL2 protein expression. Lymph nodes collected from 20 patients, who underwent surgery for suspected malignancy,were investigated. Imaging of tissue areas from about 400 ?m2 up to 2mm2 was performed collectingRaman maps containing thousands of spectra. Partial least squares discriminant analysis (PLS-DA) - a bilinearclassification method - was used to calculate lymph node classification models, in order to discriminate at firstbetween benign and malignant tissues and successively among cancer types, grades and the BCL2 protein expression.This proof-of-concept study paves the way for the development of clinical optical biopsy tools forlymph node cancer diagnosis, complementary to histopathological assessment.