Diagnosis of penile cancer with ex vivo fluorescence confocal microscopy using the Histolog® Scanner

To evaluate the feasibility and diagnostic performance of ex vivo fluorescence confocal microscopy (FCM) using the Histolog® Scanner (SamanTree Medical SA, Lausanne, Switzerland) for the assessment of penile cancer (PeCa) specimens, and to compare FCM-based diagnoses with standard formalin-fixed, paraffin-embedded (FFPE) histopathology.

We conducted a single-centre study including 12 patients with clinical or radiological suspicion of PeCa who underwent diagnostic or excisional biopsy between June 2022 and November 2023. Fresh biopsy specimens were stained with a nuclear fluorescent dye and scanned ex vivo with the Histolog Scanner. Digital images were retrospectively reviewed by two uropathologists and compared with conventional haematoxylin and eosin-stained FFPE sections. The primary endpoint was diagnostic concordance between FCM and histopathology in detecting invasive squamous cell carcinoma (SCC); secondary endpoints included sensitivity, specificity, and overall feasibility of image acquisition.

A total of 29 FCM scans were obtained. Diagnostic image quality was achieved in 28/29 scans (96.6%). FFPE analysis confirmed invasive SCC in eight patients, differentiated penile intraepithelial neoplasia in three, and an atypical squamous proliferative lesion (ASPL) in one. FCM correctly identified tumour category in 11/12 patients, yielding an overall accuracy of 91.7% (95% confidence interval [CI] 61.5-99.8%). Sensitivity for invasive SCC detection was 87.5% (7/8; 95% CI 47.3-99.7%), and specificity was 100% (4/4; 95% CI 39.8-100%). One SCC was misclassified as ASPL on FCM. Median workflow time was ~5 min/specimen.

Ex vivo FCM is a feasible, rapid imaging technique that enables high concordance with histopathology for the diagnosis of PeCa. This pilot study represents the first assessment of ex vivo FCM in penile malignancies and provides preliminary evidence supporting its potential role in intraoperative margin assessment. Larger prospective studies are required to confirm its diagnostic accuracy and clinical utility.