This is a prospective study including patients ( ≥ 18 years) referred for surgical treatment of primary cutaneous squamous cell carcinoma at the Department of Plastic Surgery, Rigshospitalet. After written and informed consent, patients will undergo standard surgical excision, followed by ex vivo 3D ultrasonography of the specimen using a 3Sonic device connected to a high-frequency ultrasound machine. This will create 3D ultrasound tomographic scans which will be interpreted by one investigator blinded to histopathology. The investigated outcomes will primarily be the deep margin distance. This will be compared to histopathology, where a pathologist - blinded to the ultrasonography results - will slice the entire specimen parallel to the ultrasound images. A third investigator will then match the histopathology images to the ultrasound images for correlation of the measured deep margins.

Inclusion Criteria:

• Adults with primary cutaneous squamous cell carcinoma.

Exclusion Criteria:

• Carcinomas located on the eyelids, vulva, penis, or perianal.
• Tumors with an anticipated excision larger than 60mm.