Standardizing Retrospective Observational Research in Cutaneous Squamous Cell Carcinoma: Expert Panel Guidelines from ITSCC.

Importance: Cutaneous squamous cell carcinoma (CSCC) is the second most common malignant disease in the US. Although it typically carries a good prognosis, a subset of CSCCs are highly aggressive, carrying regional and distant metastatic potential. Due to its high incidence, this aggressive subset is responsible for considerable mortality, with an overall annual mortality estimated to equal or even surpass melanoma. Despite this morbidity, CSCC is excluded from national cancer registries, making it difficult to study its epidemiology and outcomes. Therefore, the bulk of the CSCC literature is composed of single-center and multi-institutional retrospective cohort analyses. Given variations in reporting measures and analyses in these studies, interpretability between studies and the ability to pool results are limited. Objective: To define standardized reporting measures for retrospective CSCC studies. Findings: An expert panel was convened to determine standardized guidelines for recording and analyzing retrospective CSCC data. A total of 13 dermatologists and dermatologic surgeons with more than 5 years of posttraining experience and considerable experience with performing CSCC outcomes research were recruited to the panel. Consensus recommendations were achieved for CSCC retrospective study reporting measures, definitions, and analyses. Conclusions and Relevance: The recommendations in this report present the potential to standardize future CSCC retrospective studies. With such standardization, future work may have greater interstudy interpretability and allow for pooled analyses.

Impact of Cutaneous Squamous Cell Carcinoma Histologic Features on Percent Interrater Agreement Regarding Tumor Differentiation.

BACKGROUND: Poor differentiation predicts adverse outcomes in cutaneous squamous cell carcinoma (CSCC), but there is no standardized, reliable grading system. OBJECTIVE: To explore which histologic features have the greatest impact on CSCC differentiation interrater agreement. MATERIALS AND METHODS: In a prior study, 40 raters graded differentiation for 45 squamous cell carcinomas, and percent interrater agreements were calculated. Cases graded as well/moderately differentiated with 100% agreement (10), those graded as poorly differentiated with ≥80% agreement (5), and those that received a variety of grades with ≤60% agreement (7) were pulled for the current study. Three raters graded individual histologic features for each case, and percent interrater agreements were calculated using both the well/moderately/poorly differentiated grading system and a dichotomized system. RESULTS: The percent interrater agreements were 34.8% for mitoses, 53% for pleomorphism, 59.1% for keratinization, 66.7% for cellular cohesion/intercellular bridges, and 78.8% for tumor edges. Percent agreements improved with dichotomous grading; the largest improvement was seen within the group of cases that had been graded as well/moderately differentiated with 100% agreement in the prior study. CONCLUSION: Future squamous cell carcinoma differentiation grading systems would benefit from eliminating mitotic rate, clearly defining how to grade other features, and dichotomous grading.

Grading differentiation in cutaneous squamous cell carcinoma: a review of the literature.

Poor differentiation is strongly associated with poor outcomes in cutaneous squamous cell carcinoma (CSCC). In addition, the National Comprehensive Cancer Network (NCCN) guidelines designate poorly differentiated tumors as "very high risk". Despite its clear prognostic implications, there is no standardized grading system for CSCC differentiation in common use today. CSCC differentiation is graded inconsistently by both dermatopathologists and Mohs surgeons, and reliability studies have demonstrated suboptimal inter- and intra-rater reliability in both of these groups. The absence of a standardized and reliable grading system has impeded the use of differentiation in CSCC staging, despite its apparent correlation with disease outcomes. We performed a comprehensive review of the literature summarizing historical CSCC differentiation grading systems, as well as grading systems in non-cutaneous head and neck SCC as a point of reference. Relevant articles were identified by searching Embase and PubMed, as well as by reviewing reference lists for additional articles and histology textbook excerpts. CSCC grading systems that were identified and summarized include the historical Broders system, the World Health Organization system, the College of American Pathologists' system, and a system described by a 2023 Delphi consensus panel of dermatopathologists.

Use of Imaging in Cutaneous Squamous Cell Carcinoma to Detect High-Risk Tumor Features, Nodal Metastasis, and Distant Metastasis: A Systematic Review.

BACKGROUND: Imaging has been shown to impact management and disease outcomes in cutaneous squamous cell carcinoma, but the literature on optimal modalities is lacking. OBJECTIVE: To perform a systematic review evaluating the performance of various imaging studies for the detection of perineural spread, bony invasion, nodal metastasis (NM), and distant metastasis in cutaneous squamous cell carcinoma. MATERIALS AND METHODS: Four databases were searched for relevant terms. Articles were included if they presented primary data on 5 or more subjects with cutaneous squamous cell carcinoma who underwent imaging to detect perineural spread, bony involvement, NM, or distant metastasis. RESULTS: Thirty studies and 1,027 subjects were included in the pooled analysis. Magnetic resonance imaging had a 94.9% sensitivity in detecting perineural spread. Computed tomography (CT) demonstrated a sensitivity of 75.7% and specificity of 98.6% in detecting bony invasion. While ultrasound, positron emission tomography-computed tomography, and CT all performed reasonably well in detecting NM, CT demonstrated the highest sensitivity (96.4%) and specificity (100%). Imaging changed management in up to 33% of cases. CONCLUSION: Imaging is useful in high-risk cutaneous squamous cell carcinoma. Magnetic resonance imaging performs best in the detection of perineural spread, and CT is the most accurate modality to detect bony invasion and NM.

Cutaneous Squamous Cell Carcinoma Outcomes in Solid Organ Transplant Recipients: A Matched Retrospective Cohort Study.

BACKGROUND: Solid organ transplant recipients with cutaneous squamous cell carcinoma (CSCC) have an increased risk of poor outcomes. However, a recent study demonstrated that immunosuppression is not an independent risk factor for these poor outcomes after controlling for primary tumor stage. OBJECTIVE: To evaluate whether transplant status is an independent risk factor for poor outcomes in CSCC. MATERIALS AND METHODS: A database of CSCCs treated at an academic center over 10 years was used to perform a retrospective cohort study comparing the risk of poor outcomes (local recurrence, regional and distant metastases, and disease-specific death) in solid organ transplant recipients and controls. Subjects were matched on age, tumor stage, sex, tumor site, and time to poor outcome. RESULTS: There were 316 tumors from 78 transplant patients and 316 tumors from 262 controls. On multivariate analysis, tumor stage and location on the head and neck were predictive of poor outcomes. There was no significant difference in the risk of poor outcomes in the transplant group versus the control group. CONCLUSION: Transplant status was not an independent risk factor for poor squamous cell carcinoma outcomes after controlling for stage, age, sex, site, and time to poor outcome.