Basal cell carcinoma: Comprehensive clinical and histopathological aspects, novel imaging tools and therapeutic approaches (Review)

Basal Cell Carcinoma: Comprehensive Review with Emphasis on Scar Tissue Manifestation and Post-Vaccination Incidence

Basal cell carcinoma (BCC) arising within scar tissue is a rare but clinically significant phenomenon. This comprehensive review aims to provide a succinct overview of the current state of knowledge regarding the etiological factors, pathogenesis, clinical presentation, and management of BCC. This study constitutes a literature review pertaining to BCC, with a particular emphasis on BCC developing within scar tissue. It also provides a clinical case presentation of a patient who had developed BCC in a BCG post-vaccination scar and a review of analogous findings available in the existing literature. Despite the fact that an array of mechanisms play a role in injury-related BCC growth, the main mechanism remains ambiguous and yet to be elucidated. The review also includes a detailed description of the various therapeutic options available for BCC, ranging from surgical interventions to novel pharmacological treatments. By examining these intersections, the review seeks to elucidate the potential mechanisms, identify risk factors, and suggest considerations for clinical practice. The findings underscore the importance of vigilant dermatological assessment in patients with scar tissue and those recently vaccinated, aiming to improve early detection and optimize management strategies for BCC.

Case report: Variability in clinical manifestations within a family with incontinentia pigmenti

Diagnosing skin diseases in children can be a complex interdisciplinary problem. Incontinentia pigmenti (IP), also known as Bloch-Sulzberger syndrome, is a rare hereditary genodermatosis related to a mutation in the IKBKG gene. We present a family case of IP described from the perspective of various specialists, including dermatologists, oncologists, geneticists, dentists, and trichologists. The peculiarity of this case is the development of squamous cell carcinoma (SCC) on the shin of a 10-year-old female patient with IP. The patient had a positive family history: her mother and two sisters also displayed clinical manifestations of IP with involvement of skin, teeth and hair. The presence of exons 4-10 deletion in the IKBKG gene in all affected females was confirmed by detailed genetic evaluation using long-range PCR, and also high degree of X-chromosome inactivation skewing was demonstrated. The family underwent a comprehensive examination and was followed up for 2 years with successful symptomatic treatment of dermatologic manifestations. Recommendations were also made regarding dental and hair problems. By the end of the follow-up period, patients had stabilized, with the exception of a 36-year-old mother who developed generalized morphea. The study demonstrates the varying expressiveness of clinical symptoms among family members and emphasizes the importance of timely diagnosis for effective management of patients with IP.

Diagnostic dilemma in pigmented basal cell carcinoma: A case report

Basal cell carcinoma (BCC) is the most common malignant skin tumor, constituting 80% of nonmelanocytic skin tumors. Intermittent exposure to ultraviolet radiation is considered a major risk factor for BCC. This study was done in 2023 at a tertiary care cancer centre in North India. Pigmented BCC is a rare entity, a histopathological and clinical variant of BCC. This entity belongs to the category of nonmelanocytic skin tumors but exhibits increased pigmentation. Increased pigmentation also creates suspicion of melanocytic tumors, seborrheic keratosis, and Discoid Lupus Erythematosus DLE. However, this diagnostic dilemma can be elicited with histopathological analysis and clinical correlation. However, to prevent basal cell carcinoma, the best is to avoid direct sunlight; if it cannot be avoided, use sunscreen.

Dynamic optical coherence tomography evaluation in locally advanced basal cell carcinoma during sonidegib treatment

BACKGROUND

Basal cell carcinoma (BCC) is the most common cancer in the Caucasian population. It has a multifactorial pathogenesis, in which constitutive activation of the Sonic Hedgehog signalling (SHH) pathway (via mutations in PTCH1 or SMO genes) represents by far the most common genetic aberration. The introduction of vismodegib and sonidegib, two SHH pathway inhibitors, changed the therapeutic approach of locally advanced and metastatic BCCs. EADO's (European Association of Dermato-Oncology) new staging system refers to these as 'difficult-to-treat' BCCs.

OBJECTIVE

The aim was to evaluate sonidegib's effectiveness in patients affected by difficult-to-treat BCCs by using non-invasive diagnostic techniques.

METHODS

We retrospectively evaluated 14 patients (4 females, 10 males; mean age 77 ± 11 years) affected by difficult-to-treat BCCs treated with oral sonidegib 200 mg/day that were followed with total body videodermoscopy (V-Track, Vidix 4.0) and dynamic optical coherence tomography (D-OCT, VivoSight Dx) since May 2022. Considering the risk of rhabdomyolysis routine blood tests, especially for creatine kinase concentrations, were performed. All treated patients were inserted in the BasoCare database, which aims to offer support to patients taking sonidegib. Complete and partial responses were evaluated by the overall reduction of the number of lesions and their individual sizes. Safety was evaluated by assessing the occurrence and severity of adverse reactions.

RESULTS

Eighty per cent achieved complete clearance and 75% reduction of diameter. D-OCT scans performed at every follow-up showed concordance with clinical appearance and demonstrated reduction of hyporeflective structures, that is, islets of tumour cells and overall improvement of morphology.

CONCLUSION

Sonidegib can be considered an effective treatment option in cases where surgery or radiotherapy would be unfeasible or has previously failed, although pigmented lesions did not show complete clearance, suggesting that there are factors other than the SHH pathway involved in tumour growth. Videodermoscopy and D-OCT were useful in the quick and seamless follow-up of lesions and added valuable information in assessing efficacy.

C. M, Sharma S. Neglected Fungating Giant basal cell carcinoma: A case report and literature review

Key Clinical Message

Gaint fungating BCC is rare and aggressive. Early health-seeking behavior may result in positive outcomes.

Abstract

Fungating giant basal cell carcinoma (BCC) is a rare and aggressive form of BCC infrequently reported in the literature. We present a giant BCC case in an old female from a rural area with a poor socioeconomic profile.

A 20 MHz Repetition Rate, Sub-Picosecond Ti-Sapphire Laser for Fiber Delivery in Nonlinear Microscopy of the Skin

Nonlinear microscopy (NM) enables us to investigate the morphology or monitor the physiological processes of the skin through the use of ultrafast lasers. Fiber (or fiber-coupled) lasers are of great interest because they can easily be combined with a handheld, scanning nonlinear microscope. This latter feature greatly increases the utility of NM for pre-clinical applications and in vivo tissue imaging. Here, we present a fiber-coupled, sub-ps Ti-sapphire laser system being optimized for in vivo, stain-free, 3D imaging of skin alterations with a low thermal load of the skin. The laser is pumped by a low-cost, 2.1 W, 532 nm pump laser and delivers 0.5-1 ps, high-peak-power pulses at a ~20 MHz repetition rate. The spectral bandwidth of the laser is below 2 nm, which results in a low sensitivity for dispersion during fiber delivery. The reduction in the peak intensity due to the increased pulse duration is compensated by the lower repetition rate of our laser. In our proof-of-concept imaging experiments, a ~1.8 m long, commercial hollow-core photonic bandgap fiber was used for fiber delivery. Fresh and frozen skin biopsies of different skin alterations (e.g., adult hemangioma, basal cell cancer) and an unaffected control were used for high-quality, two-photon excitation fluorescence microscopy (2PEF) and second-harmonic generation (SHG) z-stack (3D) imaging.

Narrow Histopathological Margins are Acceptable in Surgical Resection of Basal Cell Carcinoma in Japanese: A Single-Center Retrospective Study

BACKGROUND

Basal cell carcinoma (BCC) is the most common cutaneous malignancy. BCCs occur mainly in exposed areas, such as the face and scalp. Therefore, surgical resection with narrow margins is highly desirable. However, narrow margins may increase the risk of positive histopathological margins. Outcomes for such treatment might be unfavorable, but evidence for such a conclusion is lacking.

METHODS

Between April 2015 and November 2023, a total of 230 Japanese cases with BCC which underwent surgical resection with 2-mm, 3-mm, or 5-mm margins were followed in our hospital. We conducted a retrospective review that focused on the recurrence rate and histopathological margins.

RESULTS

Recurrence was recorded if the follow-up time was longer than 3 months. One of the 198 cases (0.5%) developed a recurrence. The mean lateral and deep histopathological margins were 2,525.4 μm (30.8-14,034.6 μm) and 3,409 μm (199.9-16,523.6 μm), respectively. Recurrence rate was associated with tumor size and clinical tumor border. However, histopathological margin was not associated with recurrence rate, even when it was less than 1,000 μm.

CONCLUSIONS

A narrow histopathological margin is acceptable for surgical resection of BCC in Japanese patients.

GATA3 Positively Correlates with BCL2 Expression in Indolent and Aggressive Histological Types of Cutaneous Basal Cell Carcinoma

OBJECTIVE

Some histological basal cell carcinoma (BCC) types demonstrate more aggressive behavior than others. They are known as high-risk BCC and are more challenging in therapy, contrary to indolent (low-risk) BCC types. Identifying novel protein markers to predict aggressiveness and potential therapeutic targets in challenging cases is recommended. GATA3 is a transcription factor critical for epithelial and lymphocytic differentiation. This study investigated the immunohistochemical expression of GATA3 in indolent and aggressive BCC and its association with BCL2 expression.

MATERIAL AND METHODS

Retrospectively collected indolent and aggressive BCC groups (24 cases each) were immunohistochemically stained with anti-GATA3 and BCL2 antibodies. The mean expression score (by area percentage) and TIL counts were determined and compared using ImageJ analysis. Stromal tumor-infiltrating lymphocytes (TIL) were counted per high-power field (HPF) on hematoxylin and eosin (H&E) staining.

RESULTS

GATA3 and BCL2 expressions were significantly higher in the indolent group than in the aggressive group. GATA3 expression significantly correlated with BCL2 score and TIL counts. Higher GATA3 expression was significantly associated with a more indolent BCC histological type, higher BCL2 expression, and higher TIL count.

CONCLUSION

GATA3 is a possible target for immunomodulation experiments to improve BCC immunotherapy outcomes.

Differentiation and risk stratification of basal cell carcinoma with deep learning on histopathologic images and measuring nuclei and tumor microenvironment features

BACKGROUND

Nuclear pleomorphism and tumor microenvironment (TME) play a critical role in cancer development and progression. Identifying most predictive nuclei and TME features of basal cell carcinoma (BCC) may provide insights into which characteristics pathologists can use to distinguish and stratify this entity.

OBJECTIVES

To develop an automated workflow based on nuclei and TME features from basaloid cell tumor regions to differentiate BCC from trichoepithelioma (TE) and stratify BCC into high-risk (HR) and low-risk (LR) subtypes, and to identify the nuclear and TME characteristics profile of different basaloid cell tumors.

METHODS

The deep learning systems were trained on 161 H&E -stained sections which contained 51 sections of HR-BCC, 50 sections of LR-BCC and 60 sections of TE from one institution (D1), and externally and independently validated on D2 (46 sections) and D3 (76 sections), from 2015 to 2022. 60%, 20% and 20% of D1 data were randomly splitted for training, validation and testing, respectively. The framework comprised four stages: tumor regions identification by multi-head self-attention (MSA) U-Net, nuclei segmentation by HoVer-Net, quantitative feature by handcrafted extraction, and differentiation and risk stratification classifier construction. Pixel accuracy, precision, recall, dice score, intersection over union (IoU) and area under the curve (AUC) were used to evaluate the performance of tumor segmentation model and classifiers.

RESULTS

MSA-U-Net model detected tumor regions with 0.910 precision, 0.869 recall, 0.889 dice score and 0.800 IoU. The differentiation classifier achieved 0.977 ± 0.0159, 0.955 ± 0.0181, 0.885 ± 0.0237 AUC in D1, D2 and D3, respectively. The most discriminative features between BCC and TE contained Homogeneity, Elongation, T-T_meanEdgeLength, T-T_Nsubgraph, S-T_HarmonicCentrality, S-S_Degrees. The risk stratification model can well predict HR-BCC and LR-BCC with 0.920 ± 0.0579, 0.839 ± 0.0176, 0.825 ± 0.0153 AUC in D1, D2 and D3, respectively. The most discriminative features between HR-BCC and LR-BCC comprised IntensityMin, Solidity, T-T_minEdgeLength, T-T_Coreness, T-T_Degrees, T-T_Betweenness, S-T_Degrees.

CONCLUSIONS

This framework hold potential for future use as a second opinion helping inform diagnosis of BCC, and identify nuclei and TME features related with malignancy and tumor risk stratification.

Advancements in Basal Cell Carcinoma Diagnosis: Non-Invasive Imaging and Multimodal Approach

(1) Background: The aim of this study was to correlate the diagnostic criteria described in dermatoscopy, ultrasonography (US), ex vivo confocal microscopy, and histology to the most common subtypes of basal cell carcinoma (BCC). (2) Methods: We conducted a prospective study including 46 BCC cases, which were analyzed with dermatoscopy using the Delta 30 dermatoscope and Vidix 4.0 videodermoscope, with US using a high-resolution 20 MHz linear probe, with confocal microscopy, along with histopathological analysis. (3) Results: This study categorized BCC by histological subtype, with nodular being the most common (84.8%) and various other subtypes represented. US measurements of tumor thickness correlated strongly with the histopathological depth of invasion index (DI). Dermatoscopy analysis revealed significant associations between specific features and BCC subtypes. The DI was directly related to arborized vessels but inversely related to short, fine telangiectasias, maple-leaf-like areas, and spoke-wheel areas. The presence of ulceration was directly related to the DI. Confocal microscopy images exhibited several characteristics, including fluorescence, nuclear crowding, peripheral palisading, clefting, increased nuclear-cytoplasmic (N/C) ratio, and a "cauliflower-like" appearance. (4) Conclusion: The advanced detection of BCC through imagistic techniques like dermatoscopy, confocal microscopy, and ultrasound improves the diagnosis and may offer valuable insights for treatment in the future by evaluating lesion characteristics.

Biomedical application of terahertz imaging technology: a narrative review

Background and Objective

Terahertz (THz) imaging has wide applications in biomedical research due to its properties, such as non-ionizing, non-invasive and distinctive spectral fingerprints. Over the past 6 years, the application of THz imaging in tumor tissue has made encouraging progress. However, due to the strong absorption of THz by water, the large size, high cost, and low sensitivity of THz devices, it is still difficult to be widely used in clinical practice. This paper provides ideas for researchers and promotes the development of THz imaging in clinical research.

Methods

The literature search was conducted in the Web of Science and PubMed databases using the keywords "Terahertz imaging", "Breast", "Brain", "Skin" and "Cancer". A total of 94 English language articles from 1 January, 2017 to 30 December, 2022 were reviewed.

Key Content and Findings

In this review, we briefly introduced the recent advances in THz near-field imaging, single-pixel imaging and real-time imaging, the applications of THz imaging for detecting breast, brain and skin tissues in the last 6 years were reviewed, and the advantages and existing challenges were identified. It is necessary to combine machine learning and metamaterials to develop real-time THz devices with small size, low cost and high sensitivity that can be widely used in clinical practice. More powerful THz detectors can be developed by combining graphene, designing structures and other methods to improve the sensitivity of the devices and obtain more accurate information. Establishing a THz database is one of the important methods to improve the repeatability and accuracy of imaging results.

Conclusions

THz technology is an effective method for tumor imaging. We believe that with the joint efforts of researchers and clinicians, accurate, real-time, and safe THz imaging will be widely applied in clinical practice in the future.

Immunologic and nonimmunologic sclerodermal skin conditions - review

Scleroderma-like cutaneous lesions have been found in many pathological conditions and they have the clinical appearance of sclerotic or scleroatrophic lesions. Affected skin biopsies described histopathological changes similar to those of scleroderma located strictly on the skin or those of systemic sclerosis. These skin lesions can be found in inflammatory diseases with autoimmune substrate (generalized morphea, chronic graft versus host disease, eosinophilic fasciitis), tissue storage diseases (scleredema, scleromyxedema, nephrogenyc systemic fibrosis, systemic amyloidosis), metabolic diseases (porphyrya cutanea tarda, phenylketonuria, hypothyroidism, scleredema diabeticorum), progeroid syndromes. Given the multiple etiologies of sclerodermal lesions, a correct differential diagnosis is necessary to establish the appropriate treatment.

Basal Cell Carcinoma Perineural Invasion and Suggestive Signs of Perineural Invasion-Findings and Perspectives

Basal cell carcinoma (BCC) is a malignant tumor with a rising incidence and is the beneficiary of several innovative evaluation techniques. Histopathology remains the gold standard for assessment, having the possibility of addressing multiple high-risk factors such as perineural invasion (PNI). The current study included a number of 244 BCC patients and targeted the identification of positive PNI and its suggestive signs, and whether they correlated or not with other high-risk tumor signs. PNI was found in 20.1% of patients, with 30.7% of patients having perineural chronic inflammation (PCI), which is a suggestive sign of PNI. PNI was also found in larger tumors, with deeper Clark levels, in high-risk BCCs and high-grade tumors. PNI and PCI are both important for pathology reporting, aiding in treatment choice and further patient management, with possibly positive outcomes concerning morbidity and mortality.

Recurrence or de novo? Intradermal Basal Cell Carcinoma of the Scrotum: A Report of Two Cases

Basal cell carcinoma (BCC) is the most common cutaneous malignancy, usually occurring in sun-exposed areas. Although BCC in the scrotal region is uncommon, it carries a higher risk of metastasis than BCC at other sites. Here, we report two cases of BCC that developed in the scrotal region: Case 1 presented as a superficial nodule and Case 2 as a subcutaneous nodule. Histopathologically, both tumors lacked continuity with the surface epidermis and formed an intradermal nodule. In Case 1, BCC occurred for the first time and presumably developed de novo. Case 2 underwent excision of a scrotal BCC 5 years previously, and the histopathological diagnosis at that time was nodular BCC. However, when the original specimen was re-examined, it was determined that, although the tumor had been completely resected, part of the lesion had moved away from the nodular area to represent a micronodular phenotype, an aggressive BCC subtype. We hypothesized that partial evolution from a nodular to a micronodular phenotype may have contributed to the recurrence of BCC in Case 2.

Basal Cell Carcinoma-A Retrospective Descriptive Study Integrated in Current Literature

Basal cell carcinoma (BCC) is considered to be the most common cancer in humans. It has a slow growth rhythm, and for this reason, metastases are rare. For our retrospective study, we selected 180 patients from those who underwent surgery for a variety of skin tumours between January 2019 and August 2022 and whose histopathological examination revealed basal cell carcinoma. All surgeries were performed by plastic surgeons at the "St. John" hospital in Bucharest. The aim of this article is to provide observational data regarding BCC-in terms of histopathology and diagnostic and therapeutic management and to integrate these data into the current knowledge of this pathology.

Non-invasive imaging techniques in presurgical margin assessment of basal cell carcinoma: Current evidence

BACKGROUND

The diagnosis of basal cell carcinoma (BCC) is based on clinical and dermoscopical features. In uncertain cases, innovative imaging techniques, such as reflectance confocal microscopy (RCM) and optical coherence tomography (OCT), have been used. The main limitation of these techniques is the inability to study deep margins. HFUS (high-frequency ultrasound) and the most recent UHFUS (ultra-high-frequency ultrasound) have been used in various applications in dermatology, but they are not yet routinely used in the diagnosis of BCC. A key point in clinical practice is to find an imaging technique that can help to reduce post-surgical recurrences with a careful presurgical assessment of the lesional margins. This technique should show high sensitivity, specificity, reproducibility and simplicity of execution. This concept is very important for the optimal management of patients who are often elderly and have many comorbidities. The aim of the paper is to analyse the characteristics of current imaging techniques and the studies in the literature on this topic.

MATERIALS AND METHODS

The authors independently searched the MEDLINE, PubMed, Embase, Scopus, ScienceDirect and Cochrane Library databases for studies looking for non-invasive imaging techniques for the presurgical margin assessment of BCC.

RESULTS

Preoperative study of the BCC subtype can help to obtain a complete excision with free margins. Different non-invasive imaging techniques have been studied for in vivo evaluation of tumour margins, comparing the histologic evaluation with a radical surgery. The possibility to study the lateral and deep margins would allow a reduction of recurrences and sparing of healthy tissue.

CONCLUSION

HFUS and UHFUS represent the most promising, non-invasive techniques for the pre-operative study of BCC facilitating the characterization of vascularization, deep lateral margins and high-risk subtypes, although they are limited by insufficient literature unlike RCM and OCT.

Clinical, Dermoscopic and Histopathological Evaluation of Basal Cell Carcinoma

INTRODUCTION

Dermoscopy aids in identifying histopathological subtypes and the presence of clinically undetectable pigmentation in basal cell carcinoma (BCC).

OBJECTIVES

To investigate the dermoscopic features of BCC subtypes and better understand non-classical dermoscopic patterns.

METHODS

Clinical and histopathological findings were recorded by a dermatologist who was blinded to the dermoscopic images. Dermoscopic images were interpreted by two independent dermatologists blinded to the patients' clinical and histopathologic diagnosis. Agreement between the two evaluators and with histopathological findings was evaluated using Cohen's kappa coefficient analysis.

RESULTS

The study included a total of 96 BBC patients with 6 histopathologic variants: nodular (n=48, 50%), infiltrative (n=14, 14.6%), mixed (n=11, 11.5%), superficial (n=10, 10.4%), basosquamous (n=10, 10.4%), and micronodular (n=3, 3.1%). Clinical and dermoscopic diagnosis of pigmented BCC showed high agreement with histopathological diagnosis. The most common dermoscopic findings according to subtype were as follows: nodular BCC: shiny white-red structureless background (85.4%), white structureless areas (75%), and arborizing vessels (70.7%); infiltrative BCC: shiny white-red structureless background (92.9%), white structureless areas (78.6%), arborizing vessels (71.4%); mixed BCC: shiny white-red structureless background (72.7%), white structureless areas (54.4%), and short fine telangiectasias (54.4%); superficial BCC: shiny white-red structureless background (100%), short fine telangiectasias (70%); basosquamous BCC: shiny white-red structureless background (100%), white structureless areas (80%), keratin masses (80%); micronodular BCC: short fine telangiectasias (100%).

CONCLUSIONS

In this study, arborizing vessels were the most common classical dermoscopic feature of BCC, while shiny white-red structureless background and white structureless areas were the most frequent non-classical dermoscopic features.

Molecular Mechanisms and Targeted Therapies of Advanced Basal Cell Carcinoma

Among human cutaneous malignancies, basal cell carcinoma is the most common. Solid advances in unveiling the molecular mechanisms of basal cell carcinoma have emerged in recent years. In Gorlin syndrome, which shows basal cell carcinoma predisposition, identification of the patched 1 gene (PTCH1) mutation was a dramatic breakthrough in understanding the carcinogenesis of basal cell carcinoma. PTCH1 plays a role in the hedgehog pathway, and dysregulations of this pathway are known to be crucial for the carcinogenesis of many types of cancers including sporadic as well as hereditary basal cell carcinoma. In this review, we summarize the clinical features, pathological features and hedgehog pathway as applied in basal cell carcinoma. Other crucial molecules, such as p53 and melanocortin-1 receptor are also discussed. Due to recent advances, therapeutic strategies based on the precise molecular mechanisms of basal cell carcinoma are emerging. Target therapies and biomarkers are also discussed.

Significance of Dermoscopy in Association with Clinical Features in Differentiation of Basal Cell Carcinoma and Benign Trichoblastic Tumours

Background: Although basal cell carcinoma (BCC) can, in the majority of cases, be diagnosed based on clinical and dermoscopic assessment, a potential overlap with benign adnexal skin tumours seems to exist, including trichoblastic tumours (TT). Methods: Retrospective analysis of clinical and dermoscopic features of benign TT and BCC cases was performed to develop a diagnostic algorithm with a potential utility in clinical practice. Results: In the study, 502 histopathologically confirmed BCC cases were compared with 61 TT (including 44 TB (72.13%), 10 TE (16.39%) and 7 DTE (11.48%]). Patients in the BCC group were statistically older (mean age was 71.4 vs. 64.4 years, respectively; p = 0.009). BCC presented generally as larger tumours (mean tumour size 11.0 vs. 8.2 mm for the TT group; p = 0.001) and was more frequently associated with clinically visible ulceration (59.4% vs. 19.7%, respectively; p < 0.001). Comparison of lesion morphology, clinically visible pigmentation, and anatomical location did not show significant differences between the analysed groups. Dermoscopically visible ulceration was significantly more common in the BCC group compared to the TT group (52.2% vs. 14.8%; p < 0.0001). Pigmented structures, specifically brown dots and brown globules, were significantly more prevalent in the TT group (32.8% vs. 11.4%; p = 0.0001 and 29.5% vs. 8.2%; p <0.0001). Similarly, TT more commonly than BCC showed the presence of cloudy/starry milia-like cysts (26.2% vs. 11.6%; p = 0.0031) and yellow globules (16.4% vs. 7.2%; p = 0.033). Conclusions: Despite differences in frequency of clinical and dermoscopic features between BCC and TT in the studied group, differential diagnosis based on these variables is not reliable. Histopathological examination remains a diagnostic gold standard in differentiation of BCC and TT.

Clinical, Dermoscopic and Microscopic Features of a "Collision Tumour" Ultimately Confirmed as a Regressing Melanoma - Lessons Learnt from a Chance Diagnosis

Spontaneous regression of malignant melanoma was first reported over a century ago. Clinically, areas of blue or grey colouration in lesions may be indicative of regression. Dermoscopy is a very useful tool for diagnosing regression. An important criterion is the blue-white scar. About 10–35% of excised melanomas show features of regression histopathologically. We present a case of regressing melanoma, with clinical and dermoscopic features suggesting a collision tumour, diagnosed histopathologically. This case might improve our knowledge of the potential clinical manifestations, and the biology, of regressing melanoma.