According to the most recent guideline of the National Comprehensive Cancer Network (NCCN), desmoplasia is considered to be a very high risk factor for recurrence, metastasis and death in cutaneous squamous cell carcinoma (cSCC). The presence of desmoplasia is assessed by dermatopathologists during histological examination of cSCCs. However, the inter-observer agreement is between dermatopathologists in the assessment of desmoplasia is unclear. Studies on inter-observer variability in the assessment of differentiation grade in cSCCs showed that there is only a weak to moderate agreement among dermatopathologists in the assessment of differentiation grade (2-4). This study aims to investigate the interobserver agreement of desmoplasia between dermatopathologists. In this prospective study, 50 cSCCs will be assessed for desmoplasia by at least eight dermatopathologists using a predefined definition.

Inclusion Criteria:

• Histological coupes of patients with a cSCC between 2010 and 2018 (both cSCC with and without desmoplasia are included)
• Treated at the Maastricht University Medical Center+ (MUMC+)in Maastricht for their cSCC
• Of which the histology is available in the MUMC+

Exclusion Criteria:

- None

The study population consists of adult patients, both male and female, who were treated at MUMC+ between 2010 and 2018 for a cSCC, with and without desmoplasia, and whose histology is available.