Cutaneous squamous cell carcinoma (cSCC) is the second most common subtype of skin cancer. The scalp is one of the most frequently affected locations and is associated with a higher rate of complications, compared to other locations. In addition, it has a characteristic thickness and anatomical structure that may influence both growth pattern and treatment of primary cSCC; while clinical peripheral margins may be easily achieved during the surgery, vertical excision of the tumor is limited by the skull. Despite having a unique anatomy, current guidelines do not contemplate specific recommendations for scalp cSCC, which leads to inconsistent decision-making in multidisciplinary committees when discussing tumors with high risk factors or with close margins. This article provides specific recommendations for the management of patients with scalp cSCC, based on current evidence, as well as those aspects in which evidence is lacking, pointing out possible future lines of research. Topics addressed include epidemiology, clinical presentation and diagnosis, imaging techniques, surgical and radiation treatments, systemic therapy for advanced cases, and follow-up. The primary focus of this review is on management of primary cSCC of the scalp with localized disease, although where relevant, some points about recurrent cSCCs or advanced disease cases are also discussed.

Background: Consensus is lacking on adequate deep histological margins in cutaneous squamous cell carcinoma (cSCC). Deep clearance for tumours located on the scalp is limited by anatomic constraints.Objective: To determine whether clear but close deep histological margins (<1 mm) confer a higher risk of recurrence in cSCCs of the scalp treated by wide local excision, compared to deep histological margins ≥1 mm.Methods: Multicentre retrospective observational cohort study and multivariate competing risk analysis to evaluate risk factors for recurrence.Results: In total, 295 patients with 338 cSCCs were included. Close deep histological margins were not associated with an increased cumulative incidence of recurrence (subhazard ratio [SHR] 1.96 [95% CI 0.87–4.41]). However, an increased risk of recurrence was observed for those tumours that presented concurrent invasion of the galea aponeurotica and close deep margins, as opposed to patients without these factors (SHR 3.52 [1.24–10.01]). Tumours with clear but close peripheral margins (<1 mm) also had higher risk of recurrence (SHR 5.01 [1.68–14.97]).Limitations: Retrospective observational study based on pathology reports.Conclusions: Deep histological margins <1 mm do not confer a greater risk of recurrence as long as the tumour is completely excised and the galea aponeurotica is not involved. Surgical excision of cSCC on the scalp should include the galea to ensure proper assessment of deep margins.