Imaging of Mohs micrographic surgery sections using full-field optical coherence tomography: a pilot study

Diagnostic accuracy of autofluorescence-Raman microspectroscopy for surgical margin assessment during Mohs micrographic surgery of basal cell carcinoma

BACKGROUND

Autofluorescence (AF)-Raman microspectroscopy is a technology that can detect residual basal cell carcinoma (BCC) on the resection margin of fresh, surgically excised tissue specimens. The technology does not require tissue fixation, staining, labelling or sectioning, and provides quantitative diagnosis maps of the surgical margins in 30 min.

OBJECTIVES

To determine the accuracy of the AF-Raman instrument in detecting incomplete BCC excisions during Mohs micrographic surgery (MMS), using histology as the reference standard.

METHODS

Skin layers from 130 patients undergoing MMS at the Nottingham University Hospitals NHS Trust (September 2022-July 2023) were investigated with the AF-Raman instrument. The layers were measured when fresh, immediately after excision. The AF-Raman results and the intraoperative assessment by Mohs surgeons were compared with a postoperative consensus-derived reference produced by three dermatopathologists. The sensitivity, specificity, and positive and negative predictive values were calculated. The study was registered with ClinicalTrials.gov (NCT03482622).

RESULTS

AF-Raman analysis was successfully completed for 125 of 130 layers and, on average, covered 91% of the specimen surface area, with the lowest surface area covered being 87% for the eyelid and the highest being 94% for forehead specimens. The AF-Raman instrument identified positive margins in 24 of 36 BCC-positive cases [67% sensitivity, 95% confidence interval (CI) 49-82] and negative margins in 65 of 89 BCC-negative cases (73% specificity, 95% CI 63-82). Only one of 12 false-negative cases was caused by misclassification by the AF-Raman algorithm. The other 11 false-negatives cases were a result of no valid Raman signal being recorded at the location of the residual BCC due to either occlusion by blood or poor contact between tissue and the cassette window. The intraoperative diagnosis by Mohs surgeons identified positive margins in 31 of 36 BCC-positive cases (86% sensitivity, 95% CI 70-95) and negative margins in 79 of 89 BCC-negative cases (89% specificity, 95% CI 81-95).

CONCLUSIONS

The AF-Raman instrument has the potential to provide intraoperative microscopic assessment of surgical margins in BCC surgery. Further improvements are required for tissue processing, to ensure complete coverage of the surgical specimens.

Bond-selective full-field optical coherence tomography

Optical coherence tomography (OCT) is a label-free, non-invasive 3D imaging tool widely used in both biological research and clinical diagnosis. Conventional OCT modalities can only visualize specimen tomography without chemical information. Here, we report a bond-selective full-field OCT (BS-FF-OCT), in which a pulsed mid-infrared laser is used to modulate the OCT signal through the photothermal effect, achieving label-free bond-selective 3D sectioned imaging of highly scattering samples. We first demonstrate BS-FF-OCT imaging of 1 µm PMMA beads embedded in agarose gel. Next, we show 3D hyperspectral imaging of up to 75 µm of polypropylene fiber mattress from a standard surgical mask. We then demonstrate BS-FF-OCT imaging on biological samples, including cancer cell spheroids and C. elegans. Using an alternative pulse timing configuration, we finally demonstrate the capability of BS-FF-OCT on imaging a highly scattering myelinated axons region in a mouse brain tissue slice.

Optical coherence tomography

During the past decade, noninvasive imaging has emerged as a valuable tool in clinical dermatology and dermatologic research. Optical coherence tomography (OCT) is one such type of noninvasive imaging. OCT uses the principle of interferometry to produce real-time images. A low-power diode laser shines infrared light onto tissues, which reflects back to an optical fiber interferometer. Using time delay and the backscattered light intensity, a two-dimensional image akin to an ultrasound is rendered. We review the history, types, and modalities of OCT, plus the many applications of frequency domain, high definition, and dynamic OCT in practice, including its utility in diagnosis, monitoring, and grading disease severity in a variety of cutaneous conditions.

Tangential excision (saucerization) of small basal and squamous cell skin cancers with formalin horizontal (en face) comprehensive margin histopathologic evaluation

BACKGROUND

Mohs surgery is not appropriate for all skin cancer removals. D&C has an unacceptable recurrence rate of 10-20%. A simple method of skin cancer removal is needed to fill the gap. Tangential excision is a more accurate, safer, and more time-efficient method to treat small basal cell and squamous cell skin cancers.

OBJECTIVE

Detail the process of performing tangential excision of skin cancers.

METHODS

A practitioner has performed this technique for 30 years. His experience is described here.

RESULTS

Tangential excision (saucerization) is an excellent method used to treat small skin cancers.

CONCLUSION

This technique should be considered as a better choice than D&C for the treatment of skin cancers which are not appropriate for Mohs surgery.

Clinical integration of fast Raman spectroscopy for Mohs micrographic surgery of basal cell carcinoma

We present the first clinical integration of a prototype device based on integrated auto-fluorescence imaging and Raman spectroscopy (Fast Raman device) for intra-operative assessment of surgical margins during Mohs micrographic surgery of basal cell carcinoma (BCC). Fresh skin specimens from 112 patients were used to optimise the tissue pre-processing and the Fast Raman algorithms to enable an analysis of complete Mohs layers within 30 minutes. The optimisation allowed >95% of the resection surface area to be investigated (including the deep and epidermal margins). The Fast Raman device was then used to analyse skin layers excised from the most relevant anatomical sites (nose, temple, eyelid, cheek, forehead, eyebrow and lip) and to detect the three main types of BCC (nodular, superficial and infiltrative). These results suggest that the Fast Raman technique is a promising tool to provide an objective diagnosis "tumour clear yes/no" during Mohs surgery of BCC. This clinical integration study is a key step towards a larger scale diagnosis test accuracy study to reliably determine the sensitivity and specificity in a clinical setting.

Ex Vivo Microscopy: A Promising Next-Generation Digital Microscopy Tool for Surgical Pathology Practice

CONTEXT.—

The rapid evolution of optical imaging modalities in recent years has opened the opportunity for ex vivo tissue imaging, which has significant implications for surgical pathology practice. These modalities have promising potential to be used as next-generation digital microscopy tools for examination of fresh tissue, with or without labeling with contrast agents.

OBJECTIVE.—

To review the literature regarding various types of ex vivo optical imaging platforms that can generate digital images for tissue recognition with potential for utilization in anatomic pathology clinical practices.

DATA SOURCES.—

Literature relevant to ex vivo tissue imaging obtained from the PubMed database.

CONCLUSIONS.—

Ex vivo imaging of tissues can be performed by using various types of optical imaging techniques. These next-generation digital microscopy tools have a promising potential for utilization in surgical pathology practice.

The clinical usefulness of optical coherence tomography during cancer interventions

INTRODUCTION

Tumor detection and visualization plays a key role in the clinical workflow of a patient with suspected cancer, both in the diagnosis and treatment. Several optical imaging techniques have been evaluated for guidance during oncological interventions. Optical coherence tomography (OCT) is a technique which has been widely evaluated during the past decades. This review aims to determine the clinical usefulness of OCT during cancer interventions focussing on qualitative features, quantitative features and the diagnostic value of OCT.

METHODS

A systematic literature search was performed for articles published before May 2018 using OCT in the field of surgical oncology. Based on these articles, an overview of the clinical usefulness of OCT was provided per tumor type.

RESULTS

A total of 785 articles were revealed by our search, of which a total of 136 original articles were available for analysis, which formed the basis of this review. OCT is currently utilised for both preoperative diagnosis and intraoperative detection of skin, oral, lung, breast, hepatobiliary, gastrointestinal, urological, and gynaecological malignancies. It showed promising results in tumor detection on a microscopic level, especially using higher resolution imaging techniques, such as high-definition OCT and full-field OCT.

CONCLUSION

In the near future, OCT could be used as an additional tool during bronchoscopic or endoscopic interventions and could also be implemented in margin assessment during (laparoscopic) cancer surgery if a laparoscopic or handheld OCT device will be further developed to make routine clinical use possible.

Optical coherence tomography for the diagnosis of malignant skin tumors: a meta-analysis

Optical coherence tomography (OCT) is an emergent imaging tool used for noninvasive diagnosis of skin diseases. The present meta-analysis was carried out to assess the accuracy of OCT for the diagnosis of skin cancer. We conducted a systematic literature search though EMBASE, Medline, PubMed, the Cochrane Library, and Web of Science database for relevant articles published up to June 6, 2017. The quality of the included studies was assessed using the QUADAS-2 tool and the Oxford Levels of Evidence Scale. Statistical analyses were conducted using the software Meta-Disc version 1.4 and STATA version 12.0. A total of 14 studies involving more than 813 patients with a total of 1958 lesions were included in our analyses. The pooled sensitivity and specificity of OCT for skin cancer diagnoses were 91.8% and 86.7%, respectively. Subgroup analysis showed that the pooled sensitivities of OCT for detecting basal cell carcinoma (BCC), squamous cell carcinoma (SCC), actinic keratosis, and malignant melanoma were 92.4%, 92.3%, 73.8%, and 81.0%, respectively. The pooled specificities were 86.9%, 99.5%, 91.5%, and 93.8%, respectively. OCT appears to be useful for the detection of BCC and SCC. It is a valuable diagnostic method when screening for early skin cancers.

Freeze artifact on full-field optical coherence tomography skin imaging

BACKGROUND/PURPOSE

Full-field optical coherence tomography (FFOCT) is an emerging imaging technique for rapid histological analysis. As FFOCT is introduced into the Mohs workflow, it is important to document the effect of tissue freezing on FFOCT images and any effect FFOCT has on frozen sections. Our study aimed to evaluate the changes on FFOCT images after tissue freezing as well as FFOCT imaging effects on frozen sectioning.

METHODS

Six normal skin specimens were imaged using FFOCT and subsequently frozen using a cryostat. The specimens were then reimaged using FFOCT and compared for any differences. To evaluate the effect of FFOCT imaging on frozen sections, five normal skin specimens were bisected and one half was imaged using FFOCT. Both halves underwent frozen sectioning and analysis.

RESULTS

Significant changes in the fat, sebaceous glands, eccrine glands, and dermal collage and minimal changes in the epidermis were seen after freezing. No effect on frozen sectioning was seen after FFOCT imaging.

CONCLUSION

As FFOCT is studied for use in Mohs, clinicians should be aware that freezing prior to imaging introduces significant artifact in the FFOCT image. If possible, specimens should undergo imaging prior to being frozen.

Optical mapping of nonmelanoma skin Cancers-A pilot clinical study

BACKGROUND AND OBJECTIVE

Nonmelanoma skin cancer (NMSC) is the most common human cancer. Because these tumors often affect the face, there is a strong need for both accurate removal of these neoplasms to prevent recurrence and maximal tissue preservation to prevent cosmetic or functional deformity. Polarization-enhanced reflectance and fluorescence imaging (PERFI) is a new bedside method that uses fluorescent chromophores to image NMSC. While the feasibility of the technique has been successfully demonstrated in ex vivo studies, this is the first pilot study to extend the use of PERFI to in vivo intraoperative imaging of NMSC.

MATERIALS AND METHODS

Subjects were recruited from a population of patients with biopsy-confirmed NMSC, scheduled for Mohs micrographic surgery. Eight cases were studied. Sterile methylene blue (MB) was diluted in anaesthetic solution and infused into the peritumoral space. Digital photographs of the lesion were taken and Mohs surgery was performed. Then, the surgical bed was re-imaged. Each excision was also imaged ex vivo and processed for routine histopathology. Optical images were processed and compared with histopathology.

RESULTS AND CONCLUSIONS

The injection of MB was well tolerated. We observed a transient blue staining of the treated area, which disappeared completely within 1 week in all of the patients. In all subjects, the contrast agent, MB, was preferentially retained in the tumor. The ex vivo images correlated well with histopathology. In vivo images qualitatively delineated the tumor margins. The results of our pilot trial indicate that PERFI may be useful for accurate and rapid delineation of NMSC during surgery. Lasers Surg. Med. 49:803-809, 2017. © 2017 Wiley Periodicals, Inc.

Implementation of fluorescence confocal mosaicking microscopy by "early adopter" Mohs surgeons and dermatologists: recent progress

Confocal mosaicking microscopy (CMM) enables rapid imaging of large areas of fresh tissue ex vivo without the processing that is necessary for conventional histology. When performed in fluorescence mode using acridine orange (nuclear specific dye), it enhances nuclei-to-dermis contrast that enables detection of all types of basal cell carcinomas (BCCs), including micronodular and thin strands of infiltrative types. So far, this technique has been mostly validated in research settings for the detection of residual BCC tumor margins with high sensitivity of 89% to 96% and specificity of 99% to 89%. Recently, CMM has advanced to implementation and testing in clinical settings by “early adopter” Mohs surgeons, as an adjunct to frozen section during Mohs surgery. We summarize the development of CMM guided imaging of ex vivo skin tissues from bench to bedside. We also present its current state of application in routine clinical workflow not only for the assessment of residual BCC margins in the Mohs surgical setting but also for some melanocytic lesions and other skin conditions in clinical dermatology settings. Last, we also discuss the potential limitations of this technology as well as future developments. As this technology advances further, it may serve as an adjunct to standard histology and enable rapid surgical pathology of skin cancers at the bedside.

Identification of cell-surface markers for detecting breast cancer cells in ovarian tissue

PURPOSE

The safety of ovarian tissue autotransplantation in oncology patients cannot be ensured, as current tumor-detection methods compromise the ovarian tissue viability. Although non-destructive methods (for instance near-infrared fluorescence imaging) can discriminate malignant from healthy tissues while leaving the examined tissues unaffected, they require specific cell-surface tumor markers. We determined which tumor markers are suitable targets for tumor-specific imaging to exclude the presence of breast cancer cells in ovarian tissue.

METHODS

Immunohistochemistry was performed on formalin-fixed, paraffin-embedded specimens of ten ovaries from premenopausal patients. Additionally, we screened a tissue microarray containing tumor tissue cores from 24 breast cancer patients being eligible for ovarian tissue cryopreservation. The following cell-surface tumor markers were tested: E-cadherin, EMA (epithelial membrane antigen), Her2/neu (human epidermal growth factor receptor type 2), αvβ6 integrin, EpCAM (epithelial cell adhesion molecule), CEA (carcinoembryonic antigen), FR-α (folate receptor-alpha), and uPAR (urokinase-type plasminogen activator receptor). For each tumor, the percentage of positive breast tumor cells was measured.

RESULTS

None of the ten ovaries were positive for any of the markers tested. However, all markers (except CEA and uPAR) were present on epithelial cells of inclusion cysts. E-cadherin was present in the majority of breast tumors: ≥90 % of tumor cells were positive for E-cadherin in 17 out of 24 tumors, and 100 % of tumor cells were positive in 5 out of 24 tumors.

CONCLUSIONS

Of the markers tested, E-cadherin is the most suitable marker for a tumor-specific probe in ovarian tissue. Methods are required to distinguish inclusion cysts from breast tumor cells.

Systematic review of optical coherence tomography usage in the diagnosis and management of basal cell carcinoma

Optical coherence tomography (OCT) is a noninvasive imaging tool used in vivo in real time for diagnosis, treatment delineation and monitoring of basal cell carcinoma (BCC). Features of BCC on OCT have been widely described and reviewed. However, the diagnostic accuracy of OCT in these various applications is unclear. We systematically reviewed the literature to assess the accuracy of OCT in diagnosis and management of BCC using the Embase and Medline databases. In total 179 unique references were identified in the initial search, of which 22 studies with 556 histologically proven BCCs were eligible. Assessment of the quality of eligible studies was undertaken using the STROBE criteria. Data extraction and quality assessment were performed independently by the two authors. This systematic review provides an overview of the clinical applications of OCT in the diagnosis and management of BCC. OCT has been suggested to be useful in the diagnosis, treatment planning and treatment monitoring of BCC. As the technology improves and its utility increases, further studies with good methodological quality will be needed to implement OCT into daily practice.

Recent advances in clinical application of optical coherence tomography of human skin

Optical coherence tomography (OCT) is an emerging noninvasive imaging method that uses infrared light and interferometric techniques. The method has become increasingly popular in skin research as well as daily dermatology practice. In the present brief review, we focused on recent (2009-2014) OCT studies on the human skin, which included a reasonable sample size and statistics. Twenty-five papers were selected and briefly described OCT of epidermal thickness, skin appendages, wound healing, extracellular matrix and skin fibrosis, vascular malformations, and skin tumors such as basal cell carcinoma, actinic keratoses, and malignant melanoma.

Assessment of Sentinel Node Biopsies With Full-Field Optical Coherence Tomography

Current techniques for the intraoperative analysis of sentinel lymph nodes during breast cancer surgery present drawbacks such as time and tissue consumption. Full-field optical coherence tomography is a novel noninvasive, high-resolution, fast imaging technique. This study investigated the use of full-field optical coherence tomography as an alternative technique for the intraoperative analysis of sentinel lymph nodes. Seventy-one axillary lymph nodes from 38 patients at Tenon Hospital were imaged minutes after excision with full-field optical coherence tomography in the pathology laboratory, before being handled for histological analysis. A pathologist performed a blind diagnosis (benign/malignant), based on the full-field optical coherence tomography images alone, which resulted in a sensitivity of 92% and a specificity of 83% (n = 65 samples). Regular feedback was given during the blind diagnosis, with thorough analysis of the images, such that features of normal and suspect nodes were identified in the images and compared with histology. A nonmedically trained imaging expert also performed a blind diagnosis aided by the reading criteria defined by the pathologist, which resulted in 85% sensitivity and 90% specificity (n = 71 samples). The number of false positives of the pathologist was reduced by 3 in a second blind reading a few months later. These results indicate that following adequate training, full-field optical coherence tomography can be an effective noninvasive diagnostic tool for extemporaneous sentinel node biopsy qualification.

A feasibility study of full-field optical coherence tomography for rapid evaluation of EUS-guided microbiopsy specimens

BACKGROUND

Rapid on-site evaluation of cytologic specimens is a way of determining the adequacy of fine-needle aspiration (FNA). However, alternatives may be useful when the presence of a cytotechnologist and/or pathologist is not possible.

OBJECTIVE

To evaluate the feasibility of using full-field optical coherence tomography (FFOCT) for FNA specimen quality assessment.

DESIGN

FFOCT images were acquired on gastric, pancreatic, pelvic, and lymph-node formalin-fixed FNA specimens and were compared with histology of the same samples.

SETTING

Pathology suite in a hospital.

PATIENTS

Fourteen patients undergoing gastric, pancreatic, pelvic, or lymph-node EUS-guided FNA biopsy.

INTERVENTIONS

FFOCT imaging on formalin-fixed samples before histologic procedures.

MAIN OUTCOME MEASUREMENTS

FFOCT imaging feasibility and visibility of normal and abnormal features on images.

RESULTS

FFOCT imaging was possible. Blood, mucus, muscle, collagen, and digestive mucosa could be identified as well as abnormal architectural features including infiltrative pancreatic ductal carcinoma and a neuroendocrine neoplasm. Lesions at the individual cell level could not be detected.

LIMITATIONS

The study was performed on a limited number of cases.

CONCLUSION

FFOCT offers rapid, noninvasive, nondestructive imaging of FNA biopsy specimens. In the future, it could be performed in the endoscopy suite to improve detection of satisfactory specimens and obviate the need for rapid on-site evaluation.

Optical coherence tomography in the diagnosis of basal cell carcinoma

Since its introduction in dermatology in the late 1990s optical coherence tomography (OCT) has been used to study many skin diseases, in particular non-melanoma skin cancer and it s precursors. Special attention has been paid to superficial basal cell carcinoma (BCC), and a number of smaller observational studies have been published. The diagnostic criteria for BCC of these studies are systematically reviewed. A systemic review of English language studies was performed using PubMed, Google Scholar and Royal Danish Library, to search for primary papers on OCT and BCC. The references of retrieved papers were searched by hand for further relevant papers. A total of 39 papers were identified (search date: 2014-01-15). 22 were excluded because they did not meet the inclusion criteria, leaving 17 papers for analysis. In 100% of the studies, rounded dark structures in the upper dermis surrounded by a hyperreflective halo possibly surrounded by a hyporeflective border and disruption of epidermal layering were described. In 53% of the reports a hyporeflective lateral tumour border was described. A range of other features were mentioned in a minority of the studies. It is suggested that these diagnostic criteria could be characteristic for identifying BCC lesions using OCT.