Stimulated Raman histology as a novel method for rapid pathologic examination of unprocessed, fresh testicular biopsies to determine seminoma.

Background: Stimulated Raman histology (SRH) is a novel microscopic technique allowing real-time, label free, high-resolution microscopic images of unprocessed, unsectioned tissue. Tissue samples are imaged in the operating room using a mobile SRH microscope. Due to SRH's pseudocoloring, the images appear like conventional H&E staining. Compared to standard histopathologic analysis, formalin fixation, staining and level cutting can be omitted holding potential to decrease the time for diagnosis.

Objective: The aim of this prospective feasibility study was to evaluate SRH in the diagnosis of seminoma.

Methods: Patients with sonographic suspicion of testicular cancer, who underwent surgical exposure of the testis, were included in this study. A small biopsy of the suspicious lesion was separated ex vivo and scanned with an SRH microscope (NIO Laser Imaging System, Invenio Imaging Inc.). Three pathologists were tested on a 40-sample set, including benign and malignant images. We assessed combined accuracy, sensitivity and specificity and concordance (Cohen's Kappa and Fleiss Kappa) for inter-rater reliability.

Results: With the use of SRH the combined accuracy in identifying malignancy was 90%, with an individual pathologist sensitivity range from 79 to 97%. The combined accuracy in identifying benign tissue was 94.4%, with an individual pathologist specificity range from 83 to 100%. Cohen's Kappa for inter-rater reliability had a range from 0.342 to 0.918, which was classified as weak to almost perfect. The scanning time was less than 180 seconds for all tissue samples.

Conclusion: Through this first-in-human feasibility study we were able to show that SRH is a reliable and rapid point of care-technique to produce high-resolution images of seminoma, which can be accurately interpreted by pathologists. After further evaluation for all testicular germ cell tumors, SRH may have an impact on clinical decision-making during interventions for testicular cancer.