P22 Clinicopathologic characteristics of metastatic cutaneous squamous cell carcinoma: a cohort study

Abstract Cutaneous squamous cell carcinoma (cSCC) is a keratinocyte tumour with excellent prognosis following early-stage surgical treatment. Nevertheless, cSCC possesses an inherent potential for locoregional and distant metastasis in approximately 4% of cases, contributing to disease-specific mortality. Recent guidance on cSCC management risk stratifies patients based on clinicopathological factors to identify those patients most at risk of metastasis. A retrospective cohort study identified 3455 cSCCs arising in 2522 patients, via review of histopathological diagnoses of cSCC at a tertiary hospital in Dublin, Ireland, between the years of 2009 and 2019. The aim of the study was to describe adequately a large cohort of patients with metastatic cSCC and investigate factors associated with metastasis. Metastatic disease was identified by histopathological and/or radiological confirmation in 116 patients, with complete data available in 105 cases. Twenty-two (21%) were female. Mean age at primary tumour diagnosis was 74.8 years and mean time to first metastasis was 0.8 years. Twenty-six (25%) patients were immunosuppressed, the commonest reason for which was haematological malignancy. Median (SD) size of the primary tumour was 36 (21.65) mm and median depth was 10 (7.43) mm. Eighty-six (82%) tumours were located on the head and neck. Seventeen (16%) of the tumours were recurrent, 58 (55%) were > 20 mm, 38 (36%) demonstrated extension beyond subcutaneous fat, 22 (21%) demonstrated lymphovascular invasion, 24 (23%) demonstrated perineural invasion of nerves > 0.1 mm in diameter and 41 (39%) tumours were poorly differentiated. Twenty-six patients developed distant metastatic disease in addition to nodal metastasis. In most patients in our cohort, AJCC 8th Edition histopathological high-risk cSCC features were absent, apart from size > 20 mm. Conversely, most patients exhibited at least one clinical high-risk cSCC feature as per the British Association of Dermatologists’ guidelines for the management of cutaneous squamous cell carcinoma, including advanced age and tumour location (Keohane SG, Botting J, Budny PG et al. British Association of Dermatologists guidelines for the management of people with cutaneous squamous cell carcinoma 2020. Br J Dermatol 2021; 184:401–14). All patients were discussed at a specialist skin multidisciplinary team meeting, with significant variability noted in preoperative imaging, depending on the primary treating specialty. This cohort illustrates the importance of risk stratification of cSCC on clinicopathological features. This facilitates management decisions and ongoing patient surveillance with a view to preventing disease-specific morbidity and mortality.