Exploring the Utilization of Imaging Modalities in the Diagnosis of Basal Cell Carcinoma: A Scoping Review

Basal cell carcinoma (BCC) is a common skin cancer that occurs due to various genetic and environmental factors. Diagnosis is made by a combination of clinical appearance, biopsy, imaging, and histopathological analysis. This review describes the current array of imaging modalities available to physicians to aid in the diagnosis of BCC. It is important to stay up-to-date with improvements in diagnostic screening, and knowledge of these options is instrumental in providing the best care to patients. Embase, Medline Industries, and PubMed were searched for articles within the past 10 years based on a search query that looked for imaging modalities used in the diagnosis and evaluation of a variety of dermatologic conditions. The search was further refined to focus on BCC and satisfy the inclusion/exclusion criteria determined by the authors. The research process was detailed in the Preferred Reporting Items for Systematic Reviews and Meta-Analyses diagram. Dermoscopy is a non-invasive in vivo microscopic technique used to evaluate skin lesions. Features of dermoscopy cannot be visualized with the naked eye, and studies found that dermoscopy increased diagnostic accuracy. Reflectance confocal microscopy (RCM) examines skin morphology, and recent studies found that 100% of patients with BCC had tumor-free margins when diagnosed with RCM. It allows for a one-stop-shop for diagnosis. Optical spectroscopy samples multiple sites without removing tissue. It helps detect subtle biophysical differences, allowing for earlier diagnosis. High-frequency ultrasound (HFUS) helps determine tumor size, structure, depth of invasion and spread. Studies found statistically significant positive correlations between depth of spread and HFUS readings. Optical coherence tomography takes cross-sectional images to analyze histopathology and morphology. It produces high-resolution images, confers slightly more accurate results than a biopsy, and expedites the treatment process through an earlier diagnosis without a biopsy.These results will advance the fields of dermatology and radiology as they describe unique uses for these imaging modalities. There are a variety of ways to use microscopy, and these techniques may be applied to many different lesions and help revolutionize the diagnosis and treatment of skin cancer and other lesions without the need for multiple, sometimes disfiguring surgical procedures. With the increase in diagnostic accuracy and decrease in diagnosis time, advanced imaging studies will become an integral part of dermatologic diagnosis and be included in future management and treatment plans, especially in the case of BCC.

Real-time Analysis of Skin Biopsy Specimens With 2-Photon Fluorescence Microscopy

Importance

Nonmelanoma skin cancers (NMSCs) are primarily diagnosed through paraffin section histologic analysis of skin biopsy specimens that requires days to weeks before a formal diagnosis is reported. Two-photon fluorescence microscopy (TPFM) has the potential for point-of-care diagnosis of NMSC and other dermatologic conditions, which could enable same-visit diagnosis and treatment.

Objective

To demonstrate that TPFM imaging of NMSC can occur within minutes of obtaining biopsies and provide similar histological features to those of conventional histology and evaluate TPFM diagnostic performance with respect to conventional histology.

Design, Setting, and Participants

This comparative effectiveness pilot study examined 29 freshly excised biopsies from confirmed NMSC lesions in patients presenting for treatment. Biopsies underwent imaging immediately with TPFM on site at Rochester Dermatologic Surgery (Victor, New York) between October 2019 and August 2021. The imaged biopsies were subsequently submitted for paraffin histology to produce coregistered images. Twelve of these coregistered image pairs (41.4%) were used as a training set. Fifteen (51.7%) were used in a masked evaluation by a board-certified dermatopathologist. Two (6.9%) were excluded from the study before evaluation because they could not be coregistered.

Main Outcomes and Measures

Sensitivity, specificity, and accuracy of TPFM for NMSC biopsies were evaluated compared with conventional histology.

Results

Fourteen of the 15 biopsy specimens (93.3%) in the evaluation set were identically diagnosed with TPFM and paraffin histology. The TPFM had 100% sensitivity (95% CI, 48%-100%), 100% specificity (95% CI, 69%-100%), and 100% accuracy (95% CI, 78%-100%) for basal cell carcinoma diagnosis. For squamous cell carcinoma diagnosis, TPFM had 89% sensitivity (95% CI, 52%-100), 100% specificity (95% CI, 54%-100%), and 93% accuracy (95% CI, 68%-100%). For overall NMSC diagnosis, TPFM had a 93% sensitivity (95% CI, 66%-100%), 100% specificity (95% CI, 3%-100%), and 93% accuracy (95% CI, 68%-100%). Examination of the 1 discordant pair revealed mismatched imaging planes as the source of error.

Conclusions and Relevance

The results of this comparative effectiveness pilot study suggest that TPFM captures histological characteristics of NMSC that are present in conventional histology, which reveals its potential as a rapid, point-of-care diagnostic alternative that does not need extensive sample preparation or retraining for image evaluation. Further validation of TPFM imaging performed for a larger cohort is needed to fully evaluate its diagnostic accuracy and potential effect within the field.

Optical coherence tomography in the assessment of cutaneous cancer margins of the face: An immediate ex vivo study

BACKGROUND

The assessment of cutaneous cancer margins intra-operatively or in the immediate postoperative phase can guide the operator into achieving clear margins. Achieving clear (tumour-free) margins following surgery is an essential factor that can reduce morbidity and disfigurement. The aim of present study was to determine the accuracy of optical coherence tomography in assessing cutaneous cancer margins of the face.

MATERIALS AND METHODS

The excised tissue specimens that were examined, in this study, were acquired from 70 patients with 70 facial cancer lesions, with no nodal disease. Forty lesions were basal cell carcinomas (150 margins; 27 tumour positive) and the remaining thirty were cutaneous squamous cell carcinomas (112 margins; 22 tumour positive). These 70 resected lesions were subjected to optical coherence tomography (OCT) in the immediate ex vivo phase to assess each specimen's four margins status (anterior, posterior, medial and lateral). Two reviewers, blinded to the diagnosis, carried out the assessment of the acquired OCT images and measured the mean thickness. Intra- and inter-reviewer agreement was also calculated.

RESULTS

On OCT, tumour-involved margins displayed sudden change in thickness associated with architectural changes. BCC-involved margins showed homogenous oval nests with dark rim and dark cysts or an empty space below dermo-epidermal junction depending on the sub-type. In the case of cutaneous SCC-involved margins, the DEJ had lost its integrity with/out the presence of small bright clusters in the papillary dermis and damage to the superficial epidermal layers. The mean thickness of the whole epidermal layer of the tumour-free margin was 128 μm, while for the BCC-involved margin 640 μm, and for the cutaneous SCC-involved margin 810 μm. The sensitivity of using OCT in examining BCC-involved margins was 88.9-92.6 % and the specificity was 96.8-98.4 %. For cutaneous SCC-involved margins, the sensitivity was 81.8-91.0 % and the specificity 85.6-91.1 %. There was "strong" inter-reviewer agreement on the BCC-involved margins, while the agreement was "moderate" for the cutaneous SCC-involved margins.

CONCLUSION

OCT provides good accuracy in identifying cutaneous cancer margins. This can potentially be used to guide and monitor resection in real-time. Tumour thickness could be measured due to the thin skin of the face, but may be more difficult to measure accurately in thick tumours and/or thick skin areas.

Ex vivo full-field cellular-resolution optical coherence tomography of basal cell carcinomas: A pilot study of quality and feasibility of images and diagnostic accuracy in subtypes

BACKGROUND

Studies have reported the application of conventional optical coherence tomography (OCT) in the diagnosis of basal cell carcinoma (BCC). The new OCT provides cellular details similar to those in pathology slides and may reduce user learning time. This study aimed to demonstrate the quality of ex vivo full-field cellular-resolution OCT images and compare the diagnostic accuracy between physicians with varying pathology experience.

MATERIALS AND METHODS

Sixty histologically confirmed BCCs were selected. Tissue samples were sectioned and scanned using OCT, and their features were compared with those of hematoxylin and eosin (H&E)-stained sections. Thirty images were selected for the test administered to dermatology residents, dermatopathology fellows, and board-certified general pathologists without any OCT experience. The pretest learning included a 3-min instruction and 10-min self-study of four BCC variants.

RESULTS

Histopathological BCC and normal histological features were clearly recognizable on the OCT images. The pathological BCC features observed in the OCT images correlated with those found in the H&E-stained sections. Seven participants completed the test. The correct answer rates of the residents, fellows, and pathologists were 71%, 68%, and 83% for BCC and 44%, 57%, and 57% for the BCC subtypes, respectively.

CONCLUSION

All the participants identified BCC in >70% cases with a learning time of only 13 minutes. The results indicated that cellular-resolution OCT provided high-quality images similar to the conventional pathology slides. Pathology experience did reflect the diagnostic accuracy. However, a longer training time is still needed at all levels to recognize the BCC subtypes correctly.

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.

Diagnostic accuracy of a new ex vivo confocal laser scanning microscope compared to H&E-stained paraffin slides for micrographic surgery of basal cell carcinoma

BACKGROUND

For safe excision of malignant skin tumours, complete negative surgical margins are mandatory. The gold standard for analysis is frozen sections or paraffin-embedded haematoxylin and eosin (H&E)-stained slides. The production of H&E-stained slides is time-consuming (>20 h) while wounds remain unclosed. An upcoming method is confocal laser scanning microscopy (CLSM), a technique that scans unfixed fresh tissue rapidly.

OBJECTIVE

Evaluation of the process to generate and analyse CLSM images and assessment of the accuracy to detect basal cell carcinoma (BCC) tissue.

METHODS

Digital microscopic images were generated by the Histolog Scanner v1 from 544 fresh specimens of 148 BCCs that had been stained with a 0.01% proflavine solution. CLSM images were compared to the histological diagnoses of the corresponding H&E-stained slides.

RESULTS

A total of 525 images could be analysed. The sensitivity was 73% (95% CI = [65.27%; 80.47%]), and the specificity was 96% (95% CI = [93.40%; 97.60%]). Detection of BCCs in punch biopsies was certainly detected (sensitivity of 100%). The median total time to generate and evaluate a CLSM image was 5.17 min (maximum 20.17 min and minimum 2.05 min). The greatest challenge was flattening the specimen to assure complete representation of the surgical margins.

CONCLUSION

Confocal laser scanning microscopy is a time-saving and very effective alternative to classical paraffin-embedded or frozen sections. Patient treatment could be improved due to shorter hospital stays or faster outpatient therapy due to reduced intervals between surgical stages. Diagnostic accuracy of the microscope used still must be improved.

Simple 3-criteria-based ex vivo confocal diagnosis of basal cell carcinoma

BACKGROUND

Fast and simple microscopic evaluation of basal cell carcinoma (BCC) together with its subtype determination would accelerate diagnostic and therapeutic procedures in dermatology including Mohs surgery.

OBJECTIVES

Assessing whether simplified 3-criteria-based ex vivo confocal microscopic (CM) examination can reliably predict BCC diagnosis and subtype. Analyzing interobserver agreement between expert and novice examiner.

METHODS

CM images of 235 skin samples from 150 patients were prospectively evaluated by 2 blinded examiners for the presence of 3 predefined BCC criteria namely presence of tumor mass, peripheral palisading and clefting.

RESULTS

Out of 235 skin samples 116 showed histological presence of BCC, confocally expert diagnosed a BCC in 110 and novice examiner in 107 samples. The overall sensitivity and specificity of detecting residual BCC was 96.6% and 98.7%, respectively. Confocally, examiners diagnosed correctly nodular BCC in 96.6%, respectively, 98.3%, superficial BCC in 96.8%, respectively, 93.5%, infiltrating BCC in 88.9%, respectively, 83.3% and other BCC subtype in 22.2%, respectively, 0% (expert and novice examiner, respectively).

CONCLUSION

Ex vivo CM allowed intraoperative examination of BCC based on only 3-criteria with high sensitivity and specificity, provided useful information on tumor subtype and showed that both experienced and non-experienced examiners may use this diagnostic approach with excellent results.

Imaging in cutaneous surgery

Skin cancer is the most commonly diagnosed cancer in the USA. Mohs micrographic surgery is a microscopically controlled surgical technique that excises lateral and deep surgical margins while also sparing function and achieving a good cosmetic outcome. Given the increasing incidence in skin cancer worldwide and its associated treatment costs, techniques are being developed to improve the time and cost efficacy of this procedure. The use of noninvasive imaging, both in vivo and ex vivo, has the potential to increase efficiency of diagnosis and surgical management of skin cancers. These devices are useful in delineating lateral and deep tumor margins prior to surgery in vivo as well as to detect residual tumor ex vivo virtually in real time.

Rapid ex vivo examination of Mohs specimens using optical coherence tomography

BACKGROUND

Mohs micrographic surgery (MMS) is an effective treatment for certain non-melanoma skin cancers. Optical coherence tomography (OCT) is a biomedical imaging modality that permits high-resolution imaging of the epidermis and dermis with the potential to detect both healthy tissue and tumour. OCT may also provide a means of detecting and differentiating between the various histological subtypes of basal cell carcinomas (BCC) in vivo.

OBJECTIVE

The aim of this prospective ex vivo study was to evaluate the efficacy of OCT in recognising healthy and pathological margins of excised BCC lesions and detecting different BCC subtypes.

METHODS

Seventy-three subjects with biopsy-proven BCCs on the facial region undergoing MMS were recruited. Narrow clinically healthy margins of the skin surrounding the tumour were included in the excisional biopsy. Biopsies were scanned with the OCT instrument immediately ex vivo and processed to obtain horizontal Mohs frozen sections and compared with their corresponding OCT images.

RESULTS

Histopathological analysis of 280 margins showed 232 tumour free margins and 48 tumour-involved margins. OCT showed very good sensitivity (81.2%) and specificity (94.3%) in detecting healthy from tumour-involved margins. OCT accuracy was 93.4%, and the intra- and inter-observer reliability was substantial (Kappa value ranged between 0.63-0.76).

CONCLUSION

This study shows the accuracy of ex vivo OCT in identifying the margin status of BCCs of the head and neck region. Moreover, this modality has demonstrated good capability in distinguishing different BCC subtypes and the potential for in vivo in situ diagnostics.

Review of intraoperative optical coherence tomography: technology and applications [Invited]

During microsurgery, en face imaging of the surgical field through the operating microscope limits the surgeon's depth perception and visualization of instruments and sub-surface anatomy. Surgical procedures outside microsurgery, such as breast tumor resections, may also benefit from visualization of the sub-surface tissue structures. The widespread clinical adoption of optical coherence tomography (OCT) in ophthalmology and its growing prominence in other fields, such as cancer imaging, has motivated the development of intraoperative OCT for real-time tomographic visualization of surgical interventions. This article reviews key technological developments in intraoperative OCT and their applications in human surgery. We focus on handheld OCT probes, microscope-integrated OCT systems, and OCT-guided laser treatment platforms designed for intraoperative use. Moreover, we discuss intraoperative OCT adjuncts and processing techniques currently under development to optimize the surgical feedback derivable from OCT data. Lastly, we survey salient clinical studies of intraoperative OCT for human surgery.

High-definition optical coherence tomography - an aid to clinical practice and research in dermatology

At present, beyond clinical assessment, the diagnosis of skin diseases is primarily made histologically. However, skin biopsies have many disadvantages, including pain, scarring, risk of infection, and sampling error. With recent advances in skin imaging technology, the clinical use of imaging methods for the practical management of skin diseases has become an option. The in vivo high-definition optical coherence tomography (HD-OCT) has recently been developed and commercialized (Skintell; Agfa, Belgium). Compared with conventional OCT, it has a higher resolution; compared with reflectance confocal microscopy, it has a shorter time for image acquisition as well as a greater penetration depth and a larger field of view. HD-OCT is promising but much work is still required to develop it from a research tool to a valuable adjunct for the noninvasive diagnosis of skin lesions. Substantial work has been done to identify HD-OCT features in various diseases but interpretation can be time-consuming and tedious. Projects aimed at automating these processes and improving image quality are currently under way.

Morphologic features of basal cell carcinoma using the en-face mode in frequency domain optical coherence tomography

BACKGROUND

Optical coherence tomography (OCT) has become a valuable non-invasive tool in the in vivo diagnosis of non-melanoma skin cancer, especially of basal cell carcinoma (BCC). Due to an updated software-supported algorithm, a new en-face mode - similar to the horizontal en-face mode in high-definition OCT and reflectance confocal microscopy - surface-parallel imaging is possible which, in combination with the established slice mode of frequency domain (FD-)OCT, may offer additional information in the diagnosis of BCC.

OBJECTIVES

To define characteristic morphologic features of BCC using the new en-face mode in addition to the conventional cross-sectional imaging mode for three-dimensional imaging of BCC in FD-OCT.

METHODS

A total of 33 BCC were examined preoperatively by imaging in en-face mode as well as cross-sectional mode in FD-OCT. Characteristic features were evaluated and correlated with histopathology findings.

RESULTS

Features established in the cross-sectional imaging mode as well as additional features were present in the en-face mode of FD-OCT: lobulated structures (100%), dark peritumoral rim (75%), bright peritumoral stroma (96%), branching vessels (90%), compressed fibrous bundles between lobulated nests ('star shaped') (78%), and intranodular small bright dots (51%). These features were also evaluated according to the histopathological subtype. In the en-face mode, the lobulated structures with compressed fibrous bundles of the BCC were more distinct than in the slice mode.

CONCLUSION

FD-OCT with a new depiction for horizontal and vertical imaging modes offers additional information in the diagnosis of BCC, especially in nodular BCC, and enhances the possibility of the evaluation of morphologic tumour features.

In vivo assessment of optical properties of basal cell carcinoma and differentiation of BCC subtypes by high-definition optical coherence tomography

High-definition optical coherence tomography (HD-OCT) features of basal cell carcinoma (BCC) have recently been defined. We assessed in vivo optical properties (IV-OP) of BCC, by HD-OCT. Moreover their critical values for BCC subtype differentiation were determined. The technique of semi-log plot whereby an exponential function becomes linear has been implemented on HD-OCT signals. The relative attenuation factor (µraf ) at different skin layers could be assessed.. IV-OP of superficial BCC with high diagnostic accuracy (DA) and high negative predictive values (NPV) were (i) decreased µraf in lower part of epidermis and (ii) increased epidermal thickness (E-T). IV-OP of nodular BCC with good to high DA and NPV were (i) less negative µraf in papillary dermis compared to normal adjacent skin and (ii) significantly decreased E-T and papillary dermal thickness (PD-T). In infiltrative BCC (i) high µraf in reticular dermis compared to normal adjacent skin and (ii) presence of peaks and falls in reticular dermis had good DA and high NPV. HD-OCT seems to enable the combination of in vivo morphological analysis of cellular and 3-D micro-architectural structures with IV-OP analysis of BCC. This permits BCC sub-differentiation with higher accuracy than in vivo HD-OCT analysis of morphology alone.

Histopathological correlates of basal cell carcinoma in the slice and en face imaging modes of high-definition optical coherence tomography

BACKGROUND

High-definition optical coherence tomography (HD-OCT) scanners have recently been developed, providing significantly higher resolution than conventional OCT.

OBJECTIVES

To assess the relationship between recently defined histopathological HD-OCT correlates of basal cell carcinomas (BCC) and possible predictors for the most common tumour subtypes.

METHODS

For HD-OCT imaging, we used the Skintell(®) device. Twenty-five BCCs were histopathologically confirmed (including both vertical and horizontal haematoxylin and eosin and Alcian blue sectioning) and correlated with HD-OCT images.

RESULTS

In the en face mode, lobulated nodules were seen in 21/25 BCCs (84%), peripheral rimming in 18/25 (72%), epidermal disarray in 18/25 (72%) and variably refractile stroma in 22/25 (88%). In the slice imaging mode, we observed destruction of layering in 19/25 (76%) BCCs. In both the slice and en face modes a significant correlation was observed between peritumoral rimming and grey/dark oval structures and lobulated nodules. Alcian blue stains showed peritumoral mucin deposits correlating with peripheral rimming around the tumour nodules. In a logistic regression model, we did not observe significant independent micromorphological HD-OCT predictors for either the solid or superficial BCC subtypes.

CONCLUSIONS

In agreement with recent studies we have demonstrated that HD-OCT using the slice and en face imaging modes can visualize histopathological correlates of BCC, and potentially aid noninvasive diagnostics. However, using HD-OCT correlation it was not possible to predict the superficial or solid BCC subtypes. For the first time we have shown that peripheral rimming in HD-OCT correlates with peritumoral mucin deposition.

[Optical coherence tomography]

Optical coherence tomography (OCT) was introduced in the 1990s in dermatology and is nowadays established as a noninvasive high-resolution technique for the in vivo evaluation of the skin. To date several studies have been successfully demonstrated the application of OCT for various dermatological questions. The main indication for OCT in the daily practice is the noninvasive diagnosis of nonmelanoma skin cancer such as actinic keratosis and basal cell carcinoma. OCT has also been shown to be a valuable tool in treatment monitoring and evaluation of therapeutic success of noninvasive treatment strategies like topical immune modulators or photodynamic treatment. Other potential applications for OCT include inflammatory diseases, microbial or parasitic infestations of the skin, e.g. scabies mites or onychomycosis. In recent years high-definition OCT devices have been developed that can potentially be used for the evaluation of melanocytic lesions and, due to the higher resolution, for the visualization of intrafollicular demodex mites. Furthermore different commercially available devices offer-in addition to the cross-sectional images-a fast-generated horizontal (en face) imaging mode. With respect to resolution and penetration depth the OCT technique is taking a middle position in comparison to other noninvasive imaging devices in dermatology such as sonography and reflectance confocal microscopy.

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.

Automated identification of basal cell carcinoma by polarization-sensitive optical coherence tomography

We report an automated classifier to detect the presence of basal cell carcinoma in images of mouse skin tissue samples acquired by polarization-sensitive optical coherence tomography (PS-OCT). The sensitivity and specificity of the classifier based on combined information of the scattering intensity and birefringence properties of the samples are significantly higher than when intensity or birefringence information are used alone. The combined information offers a sensitivity of 94.4% and specificity of 92.5%, compared to 78.2% and 82.2% for intensity-only information and 85.5% and 87.9% for birefringence-only information. These results demonstrate that analysis of the combination of complementary optical information obtained by PS-OCT has great potential for accurate skin cancer diagnosis.

Noninvasive monitoring of basal cell carcinomas treated with systemic hedgehog inhibitors: pseudocysts as a sign of tumor regression

BACKGROUND

Oral hedgehog inhibitors (HHIs) have shown significant efficacy in the treatment of basal cell carcinoma (BCC). The evaluation of tumor regression has been performed using clinical photography and radiographic scans. Noninvasive imaging techniques, such as reflectance confocal microscopy (RCM) and high-definition optical coherence tomography (HD-OCT), have been shown to be valuable in detecting BCC in the skin.

OBJECTIVE

We monitored HHI-treated BCC using RCM and HD-OCT in vivo and correlated morphologic changes seen on imaging to changes in traditional histopathology.

METHODS

Six BCCs in 5 patients receiving HHIs (vismodegib or sonidegib) were examined by RCM and HD-OCT before and during treatment. Characteristic features were compared to histopathologic findings, including immunohistochemical analysis.

RESULTS

Characteristic features of BCC in RCM and HD-OCT decreased or disappeared completely during HHI treatment. Half of the clinically complete responding tumors still featured tumor residue. Pseudocystic structures ("empty" tumor nests in imaging) and widespread fibrosis (coarse bright fibers) were new findings and could be confirmed by histopathology.

LIMITATIONS

Our study was limited by the number of tumor samples and imaging timepoints.

CONCLUSION

Using RCM and HD-OCT, HHI-induced regression of BCC can be visualized noninvasively in the skin. The formation of pseudocysts and fibrosis were characteristic signs of BCC response to HHIs.