DS08: Slow Mohs surgery for lentigo maligna: a single-centre retrospective analysis of 159 cases

Anisha Bandyopadhyay,¹ Zhenli Kwan,^1,2 Rakesh Patalay¹ and Emma Craythorne¹

¹Dermatological Surgery and Laser Unit, St John’s Institute of Dermatology, Guy’s Hospital, London, UK; and ²Division of Dermatology, Department of Medicine, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia

Lentigo maligna (LM) is a subtype of melanoma in situ occurring on sun-damaged sites and cosmetically sensitive areas. Several treatment options are recognized with slow Mohs surgery reporting among the lowest recurrence rates (0·3–33%). We retrospectively analysed the data for 159 patients who were operated on between 13 September 2010 and 2 August 2021 at our institution. Median patient age was 69·1 years [interquartile range (IQR) 61·1–75·3]. The male : female ratio was 0·53 and most lesions were on the face (86·1%; n = 137). Mean (SD) duration of follow-up was of 59·2 (34·7) months and 67·1 (32·6) months for primary and recurrent lesions, respectively. At presentation, 73·0% (n = 116) were primary lesions and 25·2% (n = 40) were recurrent, with data missing for 1·9% (n = 3) of cases. The median preoperative clinical lesion size was 21·0 mm (IQR 13·0–28·3) for primary lesions and 31·0 mm (IQR 14·0–42·0) for recurrent lesions. The median number of slow Mohs stages was 2 (IQR 1–3) for primary lesions and 3 (IQR 2–3) for recurrent lesions. Altogether, 153/159 patients had clearance data. Ninety-seven per cent (n = 109) and 86·8% (n = 33) achieved clearance in primary and recurrent lesions, respectively. Median defect size was 33 mm (IQR 25–45) for primary lesions and 49 mm (IQR 36–60) for recurrent lesions. The histological presence of residual disease was seen in 9·2% of cases (n = 14/153) postoperatively. Six cases (3·9%) had further tissue taken during reconstruction, clearing three cases and two patients (1·3%) choosing postoperative adjuvant imiquimod therapy. Patients with residual disease had a higher number of stages (P = 0·014) and a larger defect size (P = 0·002). Clinical recurrence was reported in 12·4% (n = 15/121) of patients during follow-up, with 8·9% in primary lesions (n = 8) and 22·6% in recurrent lesions (n = 7). This difference was not statistically significant (P = 0·060). Residual disease was not statistically associated with clinical recurrence. Patients were contacted to complete a telephone survey regarding cosmetic outcomes. In total, 119/159 patients responded: 48·7% (n = 58) scored 5 (most satisfied) and 25·2% (n = 30) scored 4 (satisfied). Twenty-six per cent (n = 31) were unsatisfied (scoring ≤ 3). Within this group, 64·5% (n = 20) had reconstruction by plastic surgery, 22·6% (n = 7) by dermatology and 12·9% (n = 4) by oculoplastic surgery. In conclusion, despite an overall histological clearance rate of 90·8%, there was a 12·4% clinical recurrence over a mean follow-up of 5 years. The histological presence of residual disease was not associated with recurrence, but with a higher number of stages and larger defect sizes. However, overall the majority were satisfied with cosmesis.