13 July 2012
Detection of basal cell carcinomas in Mohs excisions with fluorescence confocal mosaicing microscopy British Journal of Dermatology
Karen J.K., Gareau D.S., Dusza S.W., Tudisco M., Rajadhyaksha M., Nehal K.S.
Background High-resolution real-time imaging of human skin is possible with a
confocal microscope either in vivo or in freshly excised tissue ex vivo. Nuclear and
cellular morphology is observed in thin optical sections, similar to that in conventional
histology. Contrast agents such as acridine orange in fluorescence and
acetic acid in reflectance have been used in ex vivo imaging to enhance nuclear
Objectives To evaluate the sensitivity and specificity of ex vivo real-time imaging
with fluorescence confocal mosaicing microscopy, using acridine orange, for the
detection of residual basal cell carcinoma (BCC) in Mohs fresh tissue excisions.
Methods Forty-eight discarded skin excisions were collected following completion
of Mohs surgery, consisting of excisions with and without residual BCC of all
major subtypes. The tissue was stained with acridine orange and imaged with a
fluorescent confocal mosaicing microscope. Confocal mosaics were matched to
the corresponding haematoxylin and eosin-stained Mohs frozen sections. Each
mosaic was divided into subsections, resulting in 149 submosaics for study. Two
Mohs surgeons, who were blinded to the cases, independently assessed confocal
submosaics and recorded the presence or absence of BCC, location, and histological
subtype(s). Assessment of confocal mosaics was by comparison with corresponding
Mohs surgery maps.
Results The overall sensitivity and specificity of detecting residual BCC was 96Æ6%
and 89Æ2%, respectively. The positive predictive value was 92Æ3% and the negative
predictive value 94Æ7%. Very good correlation was observed between confocal
mosaics and matched Mohs frozen sections for benign and malignant skin
structures, overall tumour burden and location, and identification of all major
histological subtypes of BCC.
Conclusions Fluorescent confocal mosaicing microscopy using acridine orange
enables detection of residual BCC of all subtypes in Mohs fresh tissue excisions
with high accuracy. This observation is an important step towards the long-term
clinical goal of using a noninvasive imaging modality for potential real-time surgical
pathology-at-the-bedside for skin and other tissues.