Intraoperative Ex Vivo Confocal Microscopy for Surgical Margin Assessment in Squamous Cell and Basal Cell Carcinoma (HISTOBLOC): Protocol for a Prospective Monocentric Pilot Study.

BACKGROUND

Accurate assessment of surgical margins is essential in the treatment of squamous cell carcinoma (SCC) of the upper aerodigestive tract or of cutaneous origin and of basal cell carcinoma (BCC). Intraoperative frozen section analysis is the current reference standard but is time-consuming and requires coordination between surgical and pathology teams. Ex vivo reflectance confocal microscopy offers rapid, real-time evaluation of surgical margins and may provide diagnostic information comparable to frozen section analysis while enabling the development of a reference atlas for tumor visualization.

OBJECTIVE

The HISTOBLOC study aims to evaluate the concordance between ex vivo confocal microscopy and intraoperative frozen section examination for assessing surgical margins in SCC and BCC. The secondary objectives are to assess diagnostic performance, time savings, clinical outcomes, and the feasibility of remote intraoperative evaluation using confocal microscopy.

METHODS

HISTOBLOC is a prospective, monocentric, single-arm pilot study conducted at the Institut de Cancérologie de Lorraine, a nonprofit comprehensive cancer center. The protocol plans on conducting a learning phase with 15 patients, followed by 30 consecutive patients, undergoing surgical excision for SCC or BCC (tumor size 1-4 cm), whose margins are assessed with both ex vivo confocal microscopy and frozen section analysis; a minimum of four margin specimens are obtained per surgical procedure. The primary end point is the concordance (sensitivity, specificity, and positive and negative predictive values) between the two methods, with frozen section as the reference standard; the secondary end point is the time required for intraoperative margin assessment. Diagnostic accuracy is analyzed for the learning curve phase, for the post-learning curve phase, and for the overall study population.

RESULTS

Recruitment began on July 26, 2023, and ended on June 4, 2025. Statistical analysis and interpretation are ongoing. The final number of participants and of margin specimens included in the analysis, together with the study findings, will be reported in a separate publication.

CONCLUSIONS

This protocol describes a study designed to determine whether ex vivo confocal microscopy can provide rapid, reliable intraoperative margin assessment comparable to frozen section analysis in head and neck and cutaneous SCC and BCC surgery.