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.

Lentiginous melanoma (lentigo maligna and lentigo maligna melanoma) in Australia: clinicopathological characteristics, management and recurrence rates after 10‐year follow‐up at a tertiary centre

“…Complex cases are more likely to be referred to a specialist Melanoma Unit, including patients with large lesions, those involving cosmetically or functionally difficult sites, or a recurrence. Therefore, our observed 38% recurrence rate over a median of 7.5 years is likely to be biased upwards to a substantial degree when compared to LM/LMM patients treated in the community 13,33 . On the other hand, the median of the long axis size of LM/LMM in our series (14 mm) was similar to a cohort study conducted in the United Kingdom, which included all patients with a LM diagnosis at the central pathology department in Leicestershire, irrespective of the referral clinic: Osborne et al reported a LM mean size of 14.4 mm with a recurrence rate of 20% at a mean follow‐up of 42 months in completely excised lesions, 35 similar to our finding of 24% recurrence rate after surgery with clear margins.…”

“…Therefore, our observed 38% recurrence rate over a median of 7.5 years is likely to be biased upwards to a substantial degree when compared to LM/LMM patients treated in the community. 13,33 On the other hand, the median of the long axis size of LM/LMM in our series (14 mm) was similar to a cohort study conducted in the United Kingdom, which included all patients with a LM diagnosis at the central pathology department in Leicestershire, irrespective of the referral clinic: Osborne et al reported a LM mean size of 14.4 mm with a recurrence rate of 20% at a mean follow-up of 42 months in completely excised lesions, 35 similar to our finding of 24% recurrence rate after surgery with clear margins. Moreover, one important distinction between our study and those previously published is that most prior studies had less than 5-year follow-up 19,20,35 ; thus, recurrence rates in the literature may be grossly underestimated.…”

“…In our experience, there is little role for adjuvant treatment with imiquimod or radiotherapy after excision because it has very limited efficiency but needs to be further investigated. 36 New techniques, such as RCM, may improve the accuracy of diagnosis, evaluation for an invasive component and margin involvement, 13 treatment planning and follow-up of LM/LMMs.…”

“…6 Lentiginous melanoma in situ and LMM represent a diagnostic challenge, as dermoscopy criteria can be non-specific [8][9][10][11] and frequently their peripheral margins are ill-defined with subclinical spread, 12 which may lead to a high rate of surgically involved margins. 13 Furthermore, recurrent LM/LMM can be very subtle both clinically and on dermoscopy, being therefore more difficult to diagnose than primary LM/LMM. 14,15 Histopathological examination is regarded as the gold standard for LM diagnosis; however, initial pathological assessment not infrequently relies on partial biopsies, which may be non-representative, particularly for large lesions.…”

“…Lentiginous melanoma in situ and LMM represent a diagnostic challenge, as dermoscopy criteria can be non‐specific 8–11 and frequently their peripheral margins are ill‐defined with subclinical spread, 12 which may lead to a high rate of surgically involved margins 13 . Furthermore, recurrent LM/LMM can be very subtle both clinically and on dermoscopy, being therefore more difficult to diagnose than primary LM/LMM 14,15 .…”