Incompletely excised lentigo maligna melanoma is associated with unpredictable residual disease: clinical features and the emerging role of reflectance confocal microscopy

Abstract

Background: Lentigo maligna/lentigo maligna melanoma (LM/LMM) poses a treatment and surgical challenge given unpredictable subclinical extension resulting in incomplete excision. Objectives: To describe the demographic, clinical and pathologic characteristics of incompletely excised LM/LMM. To evaluate the potential role of reflectance confocal microscopy (RCM). Patients and methods: A retrospective review of a melanoma database at a tertiary cancer centre for patients referred with ‘incompletely excised LM/LMM’ or ‘incompletely excised melanoma’ between October 2006 and July 2017. We recorded clinical and pathological data and surgical margins needed to clear the residual LM/LMM. The second part consisted of a prospective cohort of patients in which RCM was performed when presenting with incompletely excised LM/LMM. Results: We included a total of 67 patients (retrospective + prospective cohort); mean age was 64.9 (standard deviation: 11.3) years and 52.2% were males. For the retrospective cohort (n = 53), the mean scar size was 3.4 cm. The average initial margins excised prior to presentation were 4.8 mm (range 3–7 mm). The average additional margin needed to clear the residual, incompletely excised LM/LMM was 7.8 mm. For the prospective cohort (n = 14), there were no differences in age, gender or size when compared to the retrospective cohort. RCM had a diagnostic accuracy of 78.6%, a sensitivity of 90.9%, a specificity of 33.3% and a positive predictive value of 83.3% for the detection of incompletely excised LM/LMM. Conclusions: Incompletely excised LM/LMM is a poorly characterized clinical–pathological scenario that may require considerable extra margins for microscopic clearance. RCM may emerge as a valuable tool for the evaluation of patients with incompletely excised LM/LMM.