Single-Cell Profiling Reveals Sustained Immune Infiltration, Surveillance, and Tumor Heterogeneity in Infiltrative Basal Cell Carcinoma

Overview of skin cancer types and prevalence rates across continents

Skin cancer is one of the most prevalent cancers in the world, and its incidence and mortality rates are increasing continuously, mostly in regions with white-skinned inhabitants. The types of skin cancer vary in their origin and clinical appearances and also differ in their extensiveness. The continents of the world have different scenarios of skin cancer prevalence. This review aims to explore the different types of skin cancer, their clinical features, and their worldwide prevalence based on the literature. Literature from different electronic databases, including Google Scholar, ResearchGate, PubMed, Scopus, Web of Science, Embase, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Elsevier, and Springer, were collected through a literature search using specific keywords such as "skin cancer", "skin cancer types", "melanoma", "non-melanoma", "skin cancer continental prevalence" or similar keywords. The search included English publications from 2000 to 2024. Melanoma skin cancer (MSC) ranks 17th in global prevalence, with the highest incidence and deaths occurring in Europe, However, Australia and New Zealand record the highest incidence and mortality rates. Asia has a lower incidence rate of melanoma, but a higher mortality rate. Superficial spreading melanoma (SSM) is the most common type of MSC. Non-melanoma skin cancers (NMSCs) have the highest incidence in North America, with the highest number of deaths occurring in Asia, Australia and New Zealand have the highest incidence rates for basal cell carcinoma (BCC). BCC is the most commonly diagnosed skin cancer worldwide and the most prevalent form of NMSCs; however, squamous cell carcinoma is the most aggressive form of NMSCs, causing more deaths. NMSCs are the most prevalent cancers worldwide, causing most skin cancer-related deaths. The prevalence of skin cancer rising globally, with several continents experiencing higher incidence and mortality rates. The types and subtypes of skin cancer are becoming more common among clinically diagnosed cancers. This review comprehensively describes skin cancer types and their prevalence worldwide. However, the actual prevalence of skin cancer in these countries should be investigated. Further research on the prevalence of skin cancer across different continents is required to develop more effective cancer management strategies and control the spread of the disease.

Metabolic Atlas of Human Eyelid Infiltrative Basal Cell Carcinoma

Purpose

Eyelid infiltrative basal cell carcinoma (iBCC) is the most common malignant tumor affecting the ocular adnexa, but studies on metabolic changes within its microenvironment and heterogeneity at the tumor invasive area are limited. This study aims to analyze metabolic differences among iBCC cell types using single-cell and spatial metabolomics analysis and to examine metabolic environment at the tumor invasive area.

Methods

Single-cell transcriptomic data of human basal cell carcinoma (BCC) were clustered and visualized using Uniform Manifold Approximation and Projection. Metabolic reprogramming was analyzed with single-cell flux estimation analysis. Spatial metabolomics data were obtained with the Timstof Flex MALDI 2 system, and Bruker software was used for region selection.

Results

Eight cell types were identified within the iBCC microenvironment. Differences between inflammatory cancer-associated fibroblasts and myofibroblastic cancer-associated fibroblasts were analyzed. Metabolic flux analysis showed increased glycolysis, glutamine, heme, and glutathione fluxes in the iBCC microenvironment. Spatial metabolomics revealed high levels of taurine, deoxy-GMP, O-phosphoethanolamine, and pyrithione. Both tumor and invasive regions had significant upregulation of fatty acid pathways, with marked increases in oleic and arachidonic acids at the invasive area. Specific upregulation of UDP-glucuronic acid and high UDP-glucose 6-dehydrogenase (UGDH) expression in the tumor region suggest UXS1 as a potential therapeutic target for iBCC.

Conclusions

This study establishes a metabolic microenvironment atlas of iBCC, revealing significant metabolic differences and the dominance of lipid and lysosome metabolism. Potential metabolic markers and characteristic substances in the invasive area offer new insights for immunotherapy and the exploration of BCC's metabolic mechanisms.

Minimizing Surgical Margins in Basal Cell Carcinoma: A Single Institution's Experience with Excision and Reconstruction Methods

Background  Basal cell carcinoma (BCC) is the predominant nonmelanocytic skin cancer, with preservation of both function and aesthetics being essential during tumor removal. Existing surgical margin guidelines primarily target ill-defined BCCs prevalent in Western countries. Therefore, this study aims to demonstrate the efficacy of surgical removal, propose modified guidelines for wide excision tailored to Asian patients, and share experiences with various reconstruction methods. Methods  This study encompasses 418 patients (447 cases) who underwent BCC excision from March 2015 to June 2023 at our institution. Wide excision extended 2 mm beyond the tumor edge universally, with an additional 2 mm resected if tumor cells persisted in the frozen biopsy, followed by appropriate reconstruction. Patient demographics, tumor features, reconstruction methods, complications, and recurrence rates were analyzed. Results  Predominantly, reconstructions involved local flaps (244), skin grafts (102), and direct closure (72). Significant differences were noted in age, location, and tumor size among these groups. The rate of second resection increased from upper to lower facial subunits, peaking at 11.1% in the lower subunit, with a statistically significant difference ( p  = 0.024). Additional resection was required in 5.50% of cases, with a significantly higher incidence of ill-defined borders, pigmentation, and the infiltrative subtype compared with others. Complications were minor; recurrence occurred in only one case, 6 months postinitial nasal dorsum surgery. Conclusion  Surgical excision is highly effective, supported by various reconstruction options. We propose narrower guidelines for wide excision considering tumor characteristics and recurrence locations, resulting in smaller defects addressed with simpler reconstruction methods.

Unraveling the landscape of non-melanoma skin cancer through single-cell RNA sequencing technology

Non-melanoma skin cancer (NMSC) mainly includes basal cell carcinoma, cutaneous squamous cell carcinoma, and Merkel cell carcinoma, showing a low mortality rate but the highest incidence worldwide. In recent decades, research has focused on understanding the pathogenesis and clinical treatments of NMSC, leading to significant advances in our knowledge of these diseases and the development of novel therapies, including immunotherapy. Nevertheless, the low to moderate objective response rate, high recurrence, and therapeutic resistance remain persistent challenges, which are partly attributable to the intratumoral heterogeneity. This heterogeneity indicates that tumor cells, immune cells, and stromal cells in the tumor microenvironment can be reshaped to a series of phenotypic and transcriptional cell states that vary in invasiveness and treatment responsiveness. The advent of single-cell RNA sequencing (scRNA-seq) has enabled the comprehensive profiling of gene expression heterogeneity at the single-cell level, which has been applied to NMSC to quantify cell compositions, define states, understand tumor evolution, and discern drug resistance. In this review, we highlight the key findings, with a focus on intratumoral heterogeneity and the mechanism of drug resistance in NMSC, as revealed by scRNA-seq. Furthermore, we propose potential avenues for future research in NMSC using scRNA-seq.

Predictors of Local Invasion in Infiltrative Basal Cell Carcinoma: Tumour Budding Outperforms the WHO Subtyping

Tumour budding (TB) correlates with increased local invasion in various neoplasms. Certain basal cell carcinomas (BCCs) exhibit local aggressiveness. Detecting adverse prognostic factors in partial biopsies could aid in identifying cases with heightened local risk. The absolute number of TB (≤ 3 tumour cells) in excision specimens of 271 infiltrative BCCs (0: absent; 1: 1-2 foci; 2: ≥ 3 foci; 3: ≥ 10 foci), the histopathological subtype and depth of infiltration, perineural invasion, and other histological features were evaluated. A significant correlation was found between TB and both depth of infiltration (rho 0.445, p < 0.001) and perineural invasion (p = 0.009). In the multivariate analysis of depth and perineural invasion (multiple regression, stepwise), TB was identified as a significant covariate together with diameter, inflammation, and perineural invasion for the former, and depth for the latter. Conversely, no correlation existed between the WHO histological subtypes (infiltrating, sclerosing, and micronodular), and depth of infiltration or perineural invasion. This study demonstrates the value of TB as a biomarker for local invasiveness in BCC. In routine practice, a count of ≥ 3 TB foci in lesions incompletely excised or with narrow tumour-free surgical margins would be a straightforward and reproducible method to guide BCC treatment.

Deciphering tumor microenvironment: CXCL9 and SPP1 as crucial determinants of tumor-associated macrophage polarity and prognostic indicators

The tumor microenvironment (TME) is an intricate system comprised of tumor cells and the surrounding cellular and non-cellular components, exerting a pivotal influence on the initiation and progression of tumors. Exhibiting dynamic and diverse compositions as well as functional states across various tumors and patients, a profound comprehension of its specific internal interactions is indispensable for formulating efficacious anti-cancer treatment strategies. Extensive interactions among various immune cell types within the TME are well-documented, with their phenotypes and abundances closely linked to clinical prognoses. TME research is progressing towards greater complexity and precision, yet, to date, no representative TME biomarkers suitable for clinical applications have been definitively identified and validated. In a recent study, the collaborative actions of CXCL9 and SPP1 (CXCL9:SPP1) were found to collectively dictate the polarity of tumor-associated macrophages (TAMs) within the TME, exerting profound effects on tumor progression and treatment responses. The mutually exclusive expression of CXCL9:SPP1 in the TME not only governs TAM polarity but also exhibits strong correlations with immune cell profiles, antitumor factors, and patient outcomes, significantly influencing prognosis. This article consolidates the significance and prospects of CXCL9:SPP1 as a novel indicator for tumor development and prognosis, while also proposing future research directions and addressing potential challenges in this promising field.

Single-cell transcriptome analysis reveals the clinical implications of myeloid-derived suppressor cells in head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSC) is the most common malignant tumor that arises in the epithelium of the head and neck regions. Myeloid-derived suppressor cells (MDSCs) are one of the tumor-infiltrating immune cell populations, which play a powerful role in inhibiting anti-tumor immune response. Herein, we employed a single-cell RNA sequencing (scRNA-seq) dataset to dissect the heterogeneity of myeloid cells. We found that SPP1 ⁺ tumor-associated macrophages (TAMs) and MDSCs were the most abundant myeloid cells in the microenvironment. By cell cluster deconvolution from bulk RNA-seq datasets of larger patient groups, we observed that highly-infiltrated MDSC was a poor prognostic marker for patients' overall survival (OS) probabilities. To better apply the MDSC OS prediction values, we identified a set of six MDSC-related genes (ALDOA, CD52, FTH1, RTN4, SLC2A3, and TNFAIP6) as the prognostic signature. In both training and test cohorts, MDSC-related prognostic signature showed a promising value for predicting patients' prognosis outcomes. Further parsing the ligand-receptor pairs of intercellular communications by CellChat, we found that MDSCs could frequently interact with cytotoxic CD8 ⁺ T cells, SPP1 ⁺ TAMs, and endothelial cells. These interactions likely contributed to the establishment of an immunosuppressive microenvironment and the promotion of tumor angiogenesis. Our findings suggest that targeting MDSCs may serve as an alternative and promising target for the immunotherapy of HNSC.