DP06: Assessment of skin shave biopsies in the diagnosis of lentigo maligna: a 12‐year study

Abstract

Desmoplasia in cutaneous squamous cell carcinoma with perineural invasion N.K. Aretz, C. Doyle, H. McKay, C. D’Arcy, A. Lally and B. Moriarty The Charles Centre for Dermatology, St. Vincent’s University Hospital, Dublin, Ireland Cutaneous squamous cell carcinoma (cSCC) is a highly prevalent cancer. Established high-risk prognostic features include tumour size, depth of invasion, site, differentiation and perineural invasion (PNI). Previous research has shown cSCC-associated desmoplasia, defined as fine-branching tumour cells at the periphery with a surrounding desmoplastic stromal reaction, to be an independent factor in recurrence and metastasis (Breuninger H, Schaumburg-Lever G, Holzschuh J, Horny HP. Desmoplastic squamous cell carcinoma of skin and vermilion surface. Cancer 1997; 79: 915–19). In a 2020 German cohort study, PNI occurred exclusively in cSCCs with desmoplasia (Haug K, Breuninger H, Metzler G et al. Prognostic impact of perineural invasion in cutaneous squamous cell carcinoma: results of a prospective study of 1,399 tumours. J Invest Dermatol 2020; 140: 1968–75). This study aimed to identify if desmoplasia was present in cSCCs with documented PNI and whether this was associated with worse clinical outcome. A database of all cSCCs excised between January 2018 and December 2019 in a single tertiary referral hospital was interrogated for tumours with histological evidence of PNI. Pathological review was undertaken to assess for associated desmoplasia as defined by Haug et al. Clinical outcomes were recorded. In total, 330 cSCCs in 290 patients were included. Median age was 78 years (range 41–98). Median length of follow-up was 18 months. Seventy per cent (n = 232) of tumours were located on the head/neck, 4 2% (n = 14) were on the trunk, 15 8% (n = 52) on the upper limb and 10 0% (n = 33) the lower limb. American Joint Committee on Cancer T stage at diagnosis was T1 in 60 9% (n = 201), T2 in 15 7% (n = 52) and T3 in 20 3% (n = 67). The Brigham and Women’s Hospital staging at diagnosis was T1 in 54 8% (n = 181), T2a in 22 4% (n = 74), T2b in 18 2% (n = 60) and T3 in 0 9% (n = 3). Lymphovascular invasion was seen in 2 4% (n = 8) of tumours. Thirty-four per cent (n = 114) were well differentiated, 48 5% (n = 160) were moderately differentiated and 17 0% (n = 56) were poorly differentiated. PNI was identified in 5 4% (n = 18) of tumours in 17 patients. Sixtyone per cent (n = 11/18) of tumours with PNI had evidence of desmoplasia. In total, 3 1% (n = 9) of patients developed disease recurrence or progression, with two deaths from cSCC. Nine per cent (n = 1/11) of patients with both PNI and desmoplasia progressed; 0% (n = 0/6) with PNI alone progressed and 2 9% (n = 8/273) of patients with neither PNI nor desmoplasia progressed with this group, accounting for both tumour-related deaths. In this cohort of cSCCs, desmoplasia was seen in the majority of tumours with PNI. In keeping with recent literature, outcomes in this cohort of patients were less favourable than in patients with PNI alone or neither histological feature. The prognostic value of the available staging systems for cSCC is controversial. On the basis of this study, routine reporting of tumour-associated desmoplasia and incorporation into disease staging may provide insight into the future behaviour of individual tumours.