British Association of Dermatologists guidelines for the management of people with cutaneous squamous cell carcinoma 2020 *

The overall objective of the guideline is to provide up-to-date, evidence-based recommendations for the management of cutaneous squamous cell carcinoma (cSCC). The document aims to: offer an appraisal of all relevant literature up to 30th January 2020, focusing on any key developments address important, practical clinical questions relating to the primary guideline objective. provide guideline recommendations and if appropriate research recommendations.


Purpose and scope
The overall objective of the guideline is to provide up-todate, evidence-based recommendations for the management of cutaneous squamous cell carcinoma (cSCC). The document aims to • offer an appraisal of all relevant literature up to 30 January 2020, focusing on any key developments, • address important, practical clinical questions relating to the primary guideline objective, and • provide guideline recommendations and if appropriate research recommendations.
The guideline is presented as a detailed review with highlighted recommendations for practical use in primary, secondary and tertiary care, in the clinic and in the appropriate skin cancer multidisciplinary team (MDT) meetings (see section 3.0). These may be either local skin MDTs (LSMDTs) or specialist skin cancer MDTs (SSMDTs), depending on the clinicopathological features of the SCC. Clinicians treating people with cSCC should be core members of the appropriate MDT or sanctioned by the MDT to treat the tumour. 1 There is also an updated patient information leaflet available on the BAD website (https://www.skinhealthinfo.org.uk/a-z-conditionstreatments/).

Exclusions
The guideline does not cover • noncutaneous primary SCC or SCC in situ (Bowen disease); there is a separate guideline for SCC in situ, 2 • mucosal SCC; for the lip the remit of this guideline stops at the vermillion border, or • secondary prevention. 3,4 Methodology This set of guidelines has been developed using the BAD's recommended methodology; 5 further information can be found in Appendix J (see Supporting Information) with reference to the AGREE II instrument (www.agreetrust. org) 6 and GRADE (https://www.gradeworkinggroup.org). Recommendations were developed for implementation in the UK National Health Service (NHS).
The guideline development group (GDG) consisted of seven consultant dermatologists (representing England, Northern Ireland, Scotland and Wales), two consultant clinical oncologists (radiation oncologists), a consultant plastic surgeon, a consultant maxillofacial surgeon, a dermatopathologist, a general practitioner, a Macmillan dermatology clinical nurse specialist, two patient representatives and a technical team (consisting of an information scientist, a guideline research fellow and a project manager providing methodological and technical support).
The GDG established several clinical questions pertinent to the scope of the guideline and a set of outcome measures of importance to patients, ranked according to the GRADE methodology 7 (see section 2.1; and Appendix A; see Supporting Information).
The GDG agreed to adopt the Royal College of Pathologists dataset for the histological reporting of cSCC. 8 Along with Public Health England, this endorses the Union for International Cancer Control 8th edition (UICC8) 9 (Tables 1 and 2), rather than the American Joint Committee on Cancer 8th edition cancer staging manual, which covers only head and neck cSCC. 10 The GDG agreed that risk is part of a spectrum and not dichotomous, and the evidence from the literature searches supported a division based on low-, high-and very high-risk status. As shown in Figure 1, this division was achieved by integrating clinical, pathological, tumour-nodesmetastasis (TNM) staging and margin criteria. A systematic literature search of the PubMed, MEDLINE, Embase and Cochrane databases was conducted by the technical team to identify key articles on cSCC from 1 January 2007 to 30 January 2020; the search terms and strategies are detailed in Appendix K (see Supporting Information). Additional references relevant to the topic were also isolated from citations in the reviewed literature and the previous versions of the guidelines. 11,12 Data extraction, critical appraisal and data synthesis were performed by the technical team, who prepared the evidence summaries, lists of excluded studies and PRISMA diagram. Evidence from included studies was rated according to the GRADE system (high, moderate, low or very low quality).
Recommendations are based on evidence drawn from systematic reviews of the literature pertaining to the clinical questions identified, following discussions with the entire GDG and factoring in all four factors that would affect their strength ratings according to the GRADE approach (i.e. balance between desirable and undesirable effects, quality of evidence, patient values and preferences, and resource allocation). All GDG members contributed towards drafting and/or reviewing the narratives and information in the guideline and supporting information documents. When there was insufficient evidence from the literature, informal consensus was reached based on the experience of the GDG.
The summary of findings with forest plots (Appendix B), clinical evidence summary (Appendix C), tables Linking the Evidence To the Recommendations (LETR) (Appendix D), GRADE evidence profiles indicating the quality of evidence (Appendix E), summary of included studies (Appendix F), narrative findings for noncomparative studies (Appendix G), PRISMA flow diagram (Appendix H) and list of excluded studies (Appendix I) are detailed in the Supporting Information. The strength of recommendation is expressed by the wording and symbols shown in Table 3.

Clinical questions and outcomes
The GDG established a number of clinical questions pertinent to the scope of the guideline (for a full review protocol see Appendix A in the Supporting Information). The GDG also established a set of outcome measures of importance to patients for each clinical question, which were ranked according to the GRADE methodology 7 by the patient representatives. This uses a nine-point scale, with outcomes ranked 9 being those the patient representatives considered most important. Outcomes ranked 9, 8 or 7 are critical for decision-making; those ranked 6, 5 or 4 are important but not critical for decision-making; and those ranked 3, 2 or 1 are the least important for decision-making. Data on these outcome measures were extracted from the included studies (Appendixes B, C, E, F and G; see Supporting Information).

Review question 1: treatment
In people with 'higher-risk' primary cSCC, how clinically effective are surgical (standard and Mohs) and nonsurgical treatments (radiotherapy and electrochemotherapy) compared with each other?

Review question 2: treatment
In people with low-risk primary cSCC how clinically effective are surgical (standard excision, Mohs, curettage and cautery, cryosurgery and carbon dioxide laser) and nonsurgical treatments (topical therapies, photodynamic therapy or radiotherapy) compared with each other or with no treatment (observation)? (Radiotherapy includes brachytherapy where appropriate.) • Convenience of treatment 9 • Cosmetic outcome 7 • Recurrence rate 7

Review question 3: surgical margin
In people with cSCC who undergo standard surgical excision, what surgical margin and surgical plane should be used?
• Lack of clinical recurrence after 5 years 9 • Lack of clinical recurrence after 2 years 9

Review question 4: involved margins
In people with cSCC who undergo excision of the primary tumour and where histological analysis shows either one or more involved or clear-but-close margins (< 1 mm), what is the appropriate subsequent management?

Review question 6: metastatic squamous cell carcinoma
In people with any metastasis from cSCC how clinically effective are standard surgical and nonsurgical treatments (chemotherapeutic therapy, radiotherapy, immunotherapy) compared with each other or with no treatment (observation)? (Radiotherapy includes brachytherapy where appropriate.) • Survivorship 9 • Recurrence rate 9 • Cosmetic outcome 7 • Convenience of treatment 7 • Patient-reported outcomes 6

Review question 7: follow-up
In people with a diagnosed higher-risk cSCC what is the appropriate follow-up period following treatment?
• Survivorship 9 • Recurrence 9 • Metastases 9 • Patient-reported outcomes 6 Note: in Mohs surgery the tumour is curetted or surgically debulked, and the defect usually excised with a small (1-2 mm) margin of surrounding skin. The patient waits with a dressed wound pending histological confirmation by the Mohs surgeon that the tumour has been completely removed. If residual tumour is identified, a further layer of tissue is removed, and the process repeated until the surgical wound is confirmed to be tumour free. The wound is then repaired by conventional surgical techniques.

Summary of recommendations
There are few randomized controlled trials (RCTs) to support the following guidelines for the management of cSCC. The following recommendations and ratings were agreed upon unanimously by the core members of the GDG and patient representatives. The recommendations cover suspected and diagnosed cSCC. All recommendations would also generally relate to children, young people and adults, unless specified otherwise. Those under 24 years of age with cSCC should be managed by the SSMDT but must additionally be referred to the appropriate children's, teenagers' or young adults' service for their specific expertise. These guidelines do not include specific recommendations for subungual or periungual SCCs.
For further information on the wording used for recommendations and strength of recommendation ratings see Table 3. The evidence for recommendations is based on the studies as listed (for details and discussion of the evidence see Appendixes B-F in the Supporting Information). The GDG recommendations relating to referral pathways are based on discussion and clinical experience, as evidence-based details are not available at the time of writing. The GDG is aware of the lack of high-quality evidence for some of these recommendations, and therefore strong recommendations with an asterisk (*) are based on available evidence, as well as consensus and specialist experience. Good practice point (GPP) recommendations are derived from informal consensus.

R1 (↑↑)
Obtain histological confirmation of cSCC lesions in the event of diagnostic uncertainty, before planning definitive treatment. This must be a representative sample of the tumour; in most instances, this will be a full-thickness incisional biopsy ideally incorporating both the peripheral and the deep margins.

R2 (GPP)
Offer discussion on the risks and benefits of all treatment options (outcomes, function, cosmesis) to people with cSCC and their families or carers and make the treatment decision together.

R3 (↑↑)
Record the maximum clinical cSCC lesion dimension prior to any diagnostic or treatment procedure (usually diameter, in millimetres), the plane of the deep-excision margin, whether it is a recurrent tumour or in field of previous R4 (GPP) Take a good-quality clinical photograph of the cSCC lesion for the patient record to aid future management and assessment of the area after healing. In multisite disease the lesions to be treated should ideally be marked on the photograph to limit the risk of wrong-site procedures.
Treatment options for primary cutaneous squamous cell carcinoma • For deeply infiltrating or fixed lesions at any site, achieving an uninvolved deep histological margin may require inclusion of one or more of the followingfascia, muscle, bone or other underlying structurewhich may be determined clinically or by imaging, or both.
• Consideration should be given to excision of a further, orientated, deep-margin specimen where possible, if there is clinical concern at the time of resection that the resection is close or incomplete.
• Whenever possible confirm uninvolved histological margins by paraffin section analysis prior to reconstruction involving complex tissue rearrangement where dressings or temporizing cover can reasonably be achieved. However, in the context of extensive ablative resections (e.g. scalp into the calvarium or abutting dura, ear-parotidtemporal bone, composite maxillofacial resections etc.) this approach is unlikely to be feasible due to immediate reconstructive requirements.
• Where there is extensive disease, and/or involvement of specific anatomical areas, consider liaising with one or more additional MDT depending on the site of the cSCC.

R8 (↑↑)
Manage and report excised cSCC specimens according to the Royal College of Pathologists dataset. 8 Multidisciplinary team discussion R9 (GPP) Document the risk status of cSCC tumour as low risk, high risk or very high risk in the patient notes ( Figure 1).
R10 (↓↓) T1 cSCC tumours excised with histologically clear margins of at least 1 mm, in the absence of other high-risk factors, do not need routine discussion at an MDT ( Figure 1). R11 (↑↑) Review the histology of people with cSCC with one or more involved or clear-but-close margins (< 1 mm) at an appropriate skin MDT (Figure 1).

R12 (↑)
Consider the risk factors for the patient and the margin, site and tumour stage in people with cSCC with one or more clear-but-close margins (< 1 mm). Consider observation in immunocompetent people with cSCC with a low-risk tumour ( Figure 1).

R13 (↑↑)
Offer further wide local excision (with likely delayed reconstruction), Mohs micrographic surgery, or adjuvant radiotherapy to people with cSCC with one or more involved margins, or close margins (< 1 mm), where patient or tumour factors confer higher risk.

R14 (GPP)
Offer active treatment to immunosuppressed people with cSCC with one or more clear-but-close (< 1 mm) or involved margins with structured follow-up and surveillance.

R15 (↑↑)
Discuss at an SSMDT people with cSCC with symptomatic perineural invasion and/or radiological evidence of perineural invasion. If discussed at a skin MDT, skull base or head and neck MDT opinion may be required. Aggressive surgical excision of the involved nerve should be the first step, where technically possible, followed by consideration of adjuvant radiotherapy. • in recurrent disease, and • in those who are immunocompromised (see R21).

R21 (↓↓)
Do not offer postoperative radiotherapy to people with completely excised T1 or T2 cSCC and with microscopic, dermal-only, nerve diameter < 0Á1 mm perineural invasion.
R22 (↑) Consider conformal radiotherapy including the entire course of the involved nerve in people with cSCC with symptomatic perineural invasion and/or radiological evidence of perineural invasion when surgery is inappropriate, after carefully weighing the benefits and side-effects from radiotherapy to such an extensive radiotherapy treatment field.

R23 (GPP)
Inform younger people with cSCC (age < 60 years), especially if they are an organ transplant recipient, of the very low risk of radiation-induced, in-field malignancy in the future. Take this risk into account when making any treatment decision.

R25 (GPP)
Review the histology of cSCC removed by curettage and cautery to identify high-risk or very high-risk features. If these are identified, the case should be discussed at an appropriate MDT regarding further management.
Locally advanced, recurrent and metastatic cutaneous squamous cell carcinoma R26 (GPP) Do not routinely offer imaging of the draining nodal basin to people with cSCC in the absence of suspected or clinically detectable regional nodal involvement. Very highrisk lesions, such as pT2 or greater lip cSCC, carry a high risk of occult metastasis and consideration can be given to highresolution ultrasound scan of the regional nodes in the clinically N0 setting.

R27 (↑↑)
Initiate an individualized SSMDT, multimodality and imaging treatment plan for people • with regional lymph node metastasis, • who are immunocompromised and with locally advanced and/or metastatic cSCC, • with in transit metastases from cSCC, and • with metastatic cSCC who have had further locoregional relapse following lymphadenectomy.

R28 (GPP)
Where assessment of the anatomical extent of a primary cSCC warrants imaging, consider including regional lymph nodes in the scan.

R29 (GPP)
Only consider sentinel lymph node biopsy for specific, high-risk cases of primary cSCC in the context of a clinical trial or SSMDT discussion. 3

R30 (GPP)
Offer ultrasound-guided fine-needle aspiration cytology to people with cSCC with clinically suspicious nodes. If they are negative and suspicion remains, this can be repeated, although core or open-biopsy histology may be required.

R31 (GPP)
Undertake high-resolution magnetic resonance imaging (MRI) of the involved area in people with cSCC with in transit metastasis or regional perineural invasion of named nerves. Discuss with a radiologist if MRI is contraindicated.
(In transit metastasis is a type of metastasis in which skin cancer spreads through a lymph vessel and begins to grow between the area of previous treatment and the nodal basin.) R32 (↑↑) Offer therapeutic regional lymphadenectomy to people with head and neck cSCC with regional lymph node metastasis. (Regional lymphadenectomy is a surgical procedure in which the lymph nodes that drain the site of the tumour are removed to an extent that has therapeutic rather than diagnostic or palliative intent. The tissue is subsequently checked under the microscope for signs of cancer.) Imaging is required preoperatively to define the extent of locoregional relapse, and to identify distant metastatic disease (also see R36). The head and neck imaging should include locoregional MRI or computed tomography (CT), and CT imaging of the chest as a minimum. The surgery should be performed by a designated surgeon who is a core member of the SSMDT pathway and compliant with prevailing multispecialty guidance.
• Where the parotid gland has proven nodal metastasis and the neck is cN0, a therapeutic parotidectomy, usually the superficial lobe alone, should be combined with an elective selective neck dissection of levels I-III. If an anterior scalp or temple primary site has proven neck nodal metastasis, consideration should be given to an elective superficial parotidectomy at the time of therapeutic neck nodal dissection.
• Where the neck has proven nodal metastasis, the therapeutic neck dissection should include levels and structures to maximize tumour clearance, while minimizing unnecessary morbidity. It may be appropriate to preserve a clinically and radiologically uninvolved level I where the primary tumour was posterior, thus to carry out a posterolateral neck dissection of levels II-V. Consideration can also be given to preservation of an uninvolved, level V where the primary tumour site was in the central lower face.
• Nodes in the superficial system, such as the occipital nodes, or external jugular node should also be included in a dissection, according to the primary site, and the identified sites of metastasis.
R33 (↑↑) Offer therapeutic regional lymphadenectomy to people with non-head and neck cSCC with regional lymph node metastases in axillary, inguinofemoral or other peripheral draining nodes. Imaging is required preoperatively to define the extent of locoregional relapse, and to identify distant metastatic disease (also see R36). In the axilla, CT imaging should include the neck, chest and axilla as a minimum and the surgery should include levels I-III. In the inguinofemoral region CT imaging should include the chest-abdomen-pelvis and to midthigh level and the surgery should include superficial and deep levels.
• Therapeutic extended ilio-inguinofemoral lymphadenectomy is indicated in those with additional iliac nodal cSCC on imaging or cytology.
• Elective extended ilio-inguinofemoral lymphadenectomy should also be considered, at the SSMDT, for people with extensive inguinofemoral relapse (multiple nodes, any > 3 cm, plus or minus extranodal extension) who do not have concurrent evidence of iliac relapse on imaging or cytology but are deemed to be at high risk of microscopic disease in the extended basin.
• Nodal disease at other ectopic sites should have individualized imaging under guidance from the SSMDT.
• The surgery should be performed by a designated surgeon of the SSMDT pathway who is compliant with prevailing multispecialty guidance.

R34 (↑↑)
Offer adjuvant radiotherapy following therapeutic regional lymphadenectomy to people with cSCC with highrisk pathology (e.g. two or more nodes, large nodes and extracapsular extension), defined by UICC8 as ≥ pN1.

R35 (GPP)
Consider surgical resection (with or without adjuvant radiotherapy) or primary radiotherapy in people with locally recurrent cSCC.
R36 (GPP) Consider regional lymphadenectomy or regional lymph node basin irradiation in selected people with cSCC for disease control even in the presence of distant metastases, especially in those undergoing multimodality treatment.

R37 (↑)
Consider immune checkpoint inhibitor treatment in people with locally advanced cSCC where curative surgery or radiotherapy is not reasonable, or those with metastatic cSCC, except patients with organ transplants or those who have significant autoimmune conditions.

R38 (↑)
Consider systemic chemotherapy or epidermal growth factor receptor (EGFR) inhibitors in people with metastatic cSCC with contraindications to immune checkpoint inhibitors. Responses are generally short lived and chemotherapy is poorly tolerated in elderly and frail people, and consideration for best supportive care should be made. EGFR inhibitors are unlicensed for cSCC in the UK.

R39 (GPP)
Consider electrochemotherapy in people with locally advanced cSCC in palliative settings if other local or systemic therapies are not appropriate.

Follow-up
R40 (↑↑) Offer access to a key worker to people with cSCC, ideally a clinical nurse specialist, as part of an ongoing treatment prevention package. 19 Provide information on the diagnosis and management of cSCC.

R41 (GPP)
Follow up people with cSCC by examining the skin and lymph node basins and with any other appropriate clinical examination.
R42 (GPP) Educate people with cSCC on self-examination (skin and lymph nodes) and sun protection by providing appropriate verbal and written information (e.g. www.bad. org.uk/leaflets).

R43 (GPP)
Offer people with low-risk cSCC a single post-treatment appointment, where appropriate, to check histopathology results, conduct skin and nodal surveillance and facilitate patient education on self-examination and surveillance of patients' own digital photographs (patient education could have already taken place at the pretreatment appointment). Provide information on the 5-year risk of developing further cSCC and on how to access a referral, including the 2-week-wait pathway back into the system if they suspect a new lesion.

R44 (GPP)
Offer people with high-risk cSCC (especially when several risk factors apply) post-treatment follow-up appointments at 4-monthly intervals for 12 months, then at 6-monthy intervals for a further 12 months. The initial follow-up should be with secondary-care clinicians to facilitate skin surveillance and patient education on self-examination.
Later appointments may be with other clinicians able to recognize recurrences and new skin cancers according to local arrangements approved by the appropriate skin MDT.

R45 (GPP)
Offer people with very high-risk cSCC post-treatment follow-up appointments at 4-monthly intervals for 24 months, then at 6-monthly intervals for a further 12 months.
The initial follow-up should be with secondary-care clinicians to facilitate skin surveillance and patient education on self-examination. Later appointments may be made with other clinicians able to recognize recurrences and new skin cancers according to local arrangements approved by the appropriate skin MDT. People who have a high risk of developing further high-risk, primary cSCC, such as organ transplant recipients, should remain under lifelong skin surveillance.

R46 (GPP)
Offer people with metastatic cSCC post-treatment follow-up appointments at 3-monthly intervals for 24 months, then at 6-monthy intervals for a further 36 months, with potential longer-term review dependent on patient factors.
Imaging should be performed on the basis of clinical findings, with SSMDT discussion if appropriate.
Insufficient evidence to support any recommendation Θ There is insufficient evidence to support any recommendation for cryotherapy, CO 2 laser or topical therapies in the treatment of cSCC.

List of key future research recommendations
The following list outlines future research recommendations (FRRs FRR8 There is a need for a review of the treatments of cSCC in those who are at increased risk of developing SCC (e.g. those with impaired immunity or genetic conditions). FRR9 The role of sentinel lymph node biopsy in the staging of very high-risk cSCC given the propensity of these tumours to metastasize.

Algorithms
The recommendations, discussions in the LETRs (Appendix D; see Supplementary Information) and consensus specialist experience were used to inform the algorithm and pathway of care (Figures 2 and 3).

Background Definition
Primary cutaneous squamous cell carcinoma (cSCC) is a malignant tumour that arises from the keratinocytes of the epidermis or its hair follicles. It is locally invasive and has the potential to metastasize. 20

Incidence and aetiology
The rate of nonmelanoma skin cancer is at least 2Á4 times higher than that of the next most common tumour in the UK, which is breast cancer. 21 Recent evidence suggests that this is still an underestimate for skin cancer due to under-reporting. 22 cSCC is the sixth most common cancer in the UK 21,22 and its incidence continues to rise, not only in the UK but also in many other countries. [22][23][24] This will have an increasing impact on planning for NHS services and on histopathology services. 22,25 Its occurrence is usually related to chronic ultraviolet (UV) exposure and is therefore especially common in people with sun-damaged skin, fair skin, albinism and xeroderma pigmentosum. Additionally, increasing longevity may also be responsible for the increasing incidence of these tumours. It may develop de novoas a result of previous exposure to UV and ionizing radiation, or chemicals such as pesticides, herbicides or arsenic; within chronic wounds, scars, burns, ulcers or sinus tracts; or from pre-existing lesions such as SCC in situ (Bowen disease). 23,24 A high incidence of aggressive cSCC is found in individuals with recessive dystrophic epidermolysis bullosa (RDEB), where it is a major cause of death. In RDEB, the aetiology of cSCC is chronic wounding, not UV exposure. Individuals with impaired immune function, for example those receiving immunosuppressive drugs following allogeneic organ transplantation or for inflammatory disease, and those with lymphoma or leukaemia, are at increased risk of this tumour. Some cSCCs are associated with human papillomavirus infection. 26 The risk of cSCC with the 'biologic' therapies (for inflammatory or haematological disease) has yet to be accurately quantified. 27,28 There is good evidence linking cSCCs with chronic actinic damage (including that from the use of tanning devices) 29 and to support sun avoidance, use of protective clothing and effective sun blocks 30 in the prevention of actinic keratoses and cSCCs. These measures are particularly important for people receiving long-term immunosuppressive medication. 31 People who have had psoralen-UVA therapy for skin conditions may also be at higher risk. 32 cSCC may also occur in patients who are being treated with BRAF inhibitors for melanoma. 33 People with organ transplants are at high risk of developing cSCC. Skin surveillance to allow early detection and treatment, and measures to prevent cSCC, should be part of their routine care. In patients with multiple, frequent or high-risk cSCCs consideration should be given to modifying immunosuppressive regimens 34,35 and the prophylactic use of systemic retinoids, [36][37][38] which may also be valuable in other high-risk groups. 39 Nicotinamide should also be considered in this situation. 40 Therapies such as topical 5-fluorouracil 41 and imiquimod, 42 and photodynamic therapy 43 may have useful roles in preventing skin dysplasia and therefore decreasing the risk of skin cancers in high-risk renal transplant recipients, but substantive evidence is awaited.

Diagnosis and investigation
Clinical presentation SCC usually presents as an indurated nodular keratinizing or crusted tumour that may ulcerate, or it may present as an ulcer without evidence of keratinization. All patients in whom there is a possibility of a cSCC should be referred urgently to an appropriately trained specialist who is attached to an LSMDT, usually in their local dermatology department's rapidaccess skin cancer clinic. 44

Diagnosis and staging
The handling of skin cancer specimens and their histopathological diagnosis and reporting should conform to the Royal College of Pathologists dataset for primary cSCC. 8 The Royal College of Pathologists and Public Health England have adopted UICC8 TNM 9 for the staging of melanoma and nonmelanoma skin cancer.

Recommended audit points
In the last 20 consecutive patients with cSCC is there clear documentation for or evidence of the 1 Name and grade of the surgeon who carried out the surgery? 2 Patient being instructed in self-examination and provided with written patient information (e.g. www.bad.org.uk/ leaflets)? 3 Site and maximum dimension (usually diameter) of the lesion? 4 Lesion being fixed or mobile beneath the skin (head, neck, trunk and limbs)? 5 Lesion having tarsal plate or lid margin involvement, or not (eyelid)? 6 Immunosuppressive status of the patient? 7 Risk status of the lesion (low risk, high risk or very high risk)? 8 Lesion having associated clinically detectable nodes, or being clinically N0? 9 Standard surgical excision, detailing a The surgical margins of excision (R6; and see below)?
Note: these are ≥ 4 mm for low-risk, ≥ 6 mm for high-risk and ≥ 10 mm for very high-risk cSCC.
b The anatomical description of the deep margin?
10 Histological margins in all planes following standard surgical excision? Note: these are defined as clear (≥ 1 mm), clear but close (< 1 mm) or involved (0 mm). 11 Appropriate follow-up protocols (R43, R45, R46 and see below) by different members of the MDT, including clinical nurse specialists? Note: follow-up schedules are low-risk: one appointment for diagnosis and education; high-risk: a follow-up every 4 months in the first year then every 6 months in the second year; and very high-risk: a follow-up every 4 months in the first and second years, then every 6 months in the third year. 12 Recording and review of histologically proven recurrence of cSCC during follow-up periods following both surgical and nonsurgical treatments?
The audit recommendation of 20 cases per department is to reduce variation in the results due to a single patient and allow benchmarking between different units (Appendix L; see Supporting Information).

Limitations of the guideline
This document has been prepared on behalf of the BAD and is based on the best data available when the document was prepared. It is recognized that under certain conditions it may be necessary to deviate from the guidelines and that the results of future studies may require some of the recommendations herein to be changed. Failure to adhere to these guidelines should not necessarily be considered negligent, nor should adherence to these recommendations constitute a defence against a claim of negligence. Limiting the review to Englishand German-language references was a pragmatic decision but the authors recognize this may exclude some important information published in other languages.

Plans for guideline revision
The proposed revision date for this set of recommendations is scheduled for 2025; where necessary, important interim changes will be updated on the BAD website.