The literatures related to CSCC were searched in Core database based on WoSCC (https://www.webofscience.com/wos/woscc/basic-search). The data from WoSCC were comprehensive and standardized, and were widely used in bibliometrics. The retrieval strategies were “Cutaneous squamous cell carcinoma (All Fields) “ and “Cutaneous squamous cell carcinoma (All Fields) “. The literature type was limited to article, the language was limited to English, the time span was set from 2012 to middle 2022, and the retrieval time was June 30, 2022.

The full records and references of all literatures and the name, publication year, country/region, institution, source publication, research direction, author, key words, address, citation of each literature were downloaded from the WoSCC in TXT file format. All the literatures were selected separately by the experts of the two teams and finally included.

At present, the development and application of big data risk control and intelligent medical treatment all involve knowledge graph (10). Knowledge mapping is an outstanding visualization method research in information, scientometrics, knowledge rules and graphic expression in recent years (11). Up to now, knowledge graph has become one of the frontiers of visualization research in various fields. Among them, VOSviewer (12, 13), a visualization software developed by Van Eck and Waltman of Leiden University in the Netherlands, and CiteSpace (14–16), a visualization software developed by Chen Chaomei, a professor of computer and Information science at Drexel University in the United States, using the Java language, have attracted much attention. In this study, CiteSpace (Version 6.1.R2), VOSviewer (Version 1.6.10) and the literature statistics tools of WoSCC database were used to sort out and analyze CSCC related literatures, and verify the results of each other to ensure the accuracy of analysis. Set different analysis parameters according to different research contents.

CiteSpace is a common tool for mapping scientific knowledge. The aim is to visualize the structure, rules and distribution of scientific knowledge, and realize the mapping of author collaboration, keyword co-occurrence and institutional cooperation. Co-occurrence clusters, key nodes and research hotspots can be dynamically identified. At present, it has been widely used in the research hotspots and cooperative network analysis of medicine and health, humanities and philosophy, economic management, engineering and technology and other disciplines.

VOSviewer can also create visualizations. The difference is that the color of the circles represents different clusters, and the length of the line between the circles represents how close they are. Export the data of visual analysis, arrange the keywords according to the order of the average occurrence time, and get the current keywords; In the coauthored analysis, authors, institutions and countries are ranked according to link strength, and authors, institutions and countries with higher cooperative strength are obtained.

The number of articles published by countries/regions, institutions, authors and journals, keyword co-occurrence and clustering, co-occurrence among authors, institutions and countries were the main analysis indicators.

After literature screening by 2 researchers, a total of 3656 literatures were finally included in this study. These literatures were cited for a total of 62359 times from 2012 to middle 2022, and the average citation times of each item was 17.06 and h-index was 89, that is, at least 89 literatures were cited for 89 times. Among them, 156 articles were about programmed cell death, and the average citation times of each item was 12.54 and h-index was 25.

The number of published papers showed a wavy upward trend. In 2013, 268 articles were published, the lowest number in the last 11 years. Since then, the number of published papers has been increasing year by year, and it peaked at 480 in 2021, as shown in Figure 1A . In 2016, studies on programmed cell death of CSCC slowly came into view, and the number of studies involved in this field increased year by year and reached its peak in 2020, with 36 published in the whole year, and 100 articles related to programmed cell death of skin cancer were published from 2020 to middle 2022, accounting for 64.10% of the included literatures, as shown in Figure 1B .

The number and trend of published literatures play an important role in understanding the research heat and development trend of a field. According to the retrieval results, the annual number and percentage of CSCC publications in the world from 2012 to middle 2022 are shown in Table 1 . In the past 11 years, the annual average number of articles published was more than 250, indicating that the research on CSCC has been the focus of scholars’ attention in the recent 11 years.

In terms of the number of publications, the United States ranked first with an amount of 1,403, accounting for 38.375% of the total number of punlications, which has an absolute advantage. The top five countries were China, Germany, Australia and Italy. More than 70 percent of the articles were published by the top five countries, as shown in Figures 2A, B . The country with the most publications on programmed cell death in skin cancer remains the United States, with 71 articles, followed by t Germany, Italy, Australia and Japan, as shown in Figure 2C .

Based on VOSViewer software, the geographic cooperation atlas of cutaneous squamous cell carcinoma research was established ( Figure 2C ), the nodes representing the United States are the largest, indicating that the United States is still the dominant country in this field. The next countries are China, the United Kingdom, Germany, Japan, etc., indicating that these countries have a certain research status in this field.

Using CiteSpace for statistical analysis, the first place is still the United States, with a centrality of 0.34, followed by the United Kingdom, Germany, France and Sweden, as shown in Table 2 . In terms of centrality, the research results of the top ranked countries are more likely to be recognized by other countries.

Studies in this field mainly focus on Dermatology (1194, 32.623%). The other main research directions were Oncology (811 articles, 22.158%), Surgery (428 articles, 11.694%), Pathology (310 articles, 8.470%), General Internal Medicine (201 articles, 5.492%). More than 80% of the literature on squamous cell carcinoma of the skin focuses were in the top 5 research directions, as shown in Figure 3 .

Most of the top 25 institutions in the field of CSCC are from western countries. Among them, Harvard University published 294 papers, which is the institution with the most publications. The University of California System published 165 papers, and the University of Texas System published 143 papers, ranking second and third respectively. University of London, Ut Md Anderson Cancer Center and University of Sydney published more than 100 papers in this field, with 111, 101 and 100 papers respectively ( Figure 4A ; Table 3 ).

According to the statistics of intermediary centrality, Queen Mary University London has the highest intermediary centrality (0.11), indicating that it is a hub connecting other institutions ( Figure 4B ).

Based on VOSviewer software, a collaboration atlas of CSCC research institutions was established. A total of 4,287 institutions were included in the study, and 63 institutions with more than 20 publications were selected to form the collaboration atlas, which was divided into 7 clusters. Among the institutions shown in Figure 4C , the total link strength value of the University of Sydney is 151, indicating that this institution has the most co-occurrence times with other institutions. As shown in Figure 4D , Massachusetts General Hospital has been cited the most times (6390 times), indicating that its literature publication quality is high and widely recognized.

In the field of programmed death of CSCC cells, Harvard University still Published the most papers (20), accounting for 12.82% of the total publications. Nivolumab in Patients with Recurrent or Metastatic Squamous Cell Carcinoma of the Head and Neck: Efficacy and Safety in CheckMate 141 by Prior Cetuximab Use is the most cited article on procedural death of skin cancer, with a total of 67 citations, published in Clinical Cancer Research, with an impact factor of 13.2. There are 19 institutions that have published more than 3 papers in this field. Except the University of Sydney, other institutions have close research exchanges. Figures 4E, F .

Harwood CA (Queen Mary University London) has published 36 papers so far. Tommasino M (World Health Organization) ranks second with 35 publications. Proby CM (University of Dundee) ranked the third with 34 publications. The author with the highest H-index was Schmults CD (Harvard University), with a total of 31 publications, and the H-index was 18, that is, Schmults CD had at least 18 literatures being cited 18 times, as shown in Figure 5A and Table 4 .

Based on VOSviewer software, an author collaboration atlas of CSSS was established. A total of 18,426 authors had published relevant literatures, and 81 authors with more than 10 literatures were selected to form an institutional collaboration atlas, which was divided into 5 clusters. Among the authors shown in Figure 5B , the yellow cluster centered on Schmults CD (Harvard University), who was cited the most times. Figure 5C indicated that Schmults CD (Harvard University) has the highest density, suggesting that his literature is of high quality and is still recognized by other authors in this field. As shown in Figure 5D , there were only 6 scientists who published more than 5 articles. Fury and Matthew G were closely associated with other authors.

Table 5 lists the top 25 journals and journals which had published the most relevant literatures in the field, as shown in Figure 6 . The top 3 journals were JOURNAL OF CUTANEOUS PATHOLOGY (128 articles), JOURNAL OF THE AMERICAN ACADEMY OF DERMATOLOGY (95 articles) and AMERICAN JOURNAL OF DERMATOLOGY DERMATOPATHOLOGY (74 articles). The top three publishers were Wiley (751 articles), Elsevier (667 articles) and Springer Nature (426 articles), which published more than 50 percent of all publications.

Keywords co-occurrence analysis was performed using VOSviewer software. 159 keywords out of 12,704 keywords were included in the network based on the inclusion criteria of more than 30 times of common occurrence, as shown in Figure 7 . According to the keyword co-occurrence atlas, studies on squamous cell carcinoma of the skin were divided into 5 categories ( Figure 7A ): mechanism (red), treatment (purple), clinical (green), cancer (blue), and genetics (yellow). As shown in Figure 7B , the closer the circle is to green, the earlier the keyword appears. The closer the circle is to yellow, the later the keyword appears. Figure 7C is the density map of keywords. The closer the color of the keyword is to yellow, the higher the frequency of keyword occurrence. Squamous cell carcinoma, cancer, head and expression are highly popular keywords.

The word frequency growth algorithm based on CiteSpace can calculate the rapid growth of professional words in a short time and analyze the development trend of the research field of CSCC ( Figure 7D ). Before 2017, the keywords that popped up were individual, mice, of the literature, vemurafenib, ras mutation, metastatic melanoma, dabrafenib, Raf inhibitor, tissue, BRAF inhibitor and braf are mostly related to mechanism therapy and prognosis. Between 2019 and 2022, improved survival, American joint committee, keratinocyte carcinoma, high risk, cutaneous metastasis, immune checkpoint inhibitor, mechanism, reconstruction, outcm, most of which were related to the tumor. Through clinical randomized and retrospective studies, the prognostic factors affecting the survival rate of patients can be identified, which can help clinicians choose more reasonable treatment plans and improve the survival rate of patients.

The word spectrum of programmed cell death keywords in CSCC was completely different from that in CSCC. The hot keywords from 2021to middle 2022 were cutaneous squamous cell carcinoma, diagnosis, pd 1, head, nivolumab and risk. The keywords in 2022 were mostly related to immunotherapy. Clinical studies of both CSCC and programmed cell death have focused on therapy ( Figure 7E ).

According to the timespan cluster map generated by CiteSpace software ( Figure 8 ), keywords in the field of CSCC from 2012 to middle 2022 can be divided into 7 clusters: cutaneous squamous cell carcinoma, sentinel lymph node biopsy, skin cancer, BRAF inhibitor, human papillomaviruses and human papillomaviruses and P63 expression. The size, average contour value and representative keywords of each cluster were shown in Table 6 . The appendix shows the specific content of keyword clustering.