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.

BACKGROUND: Lentiginous melanoma or lentigo maligna is a slow-growing type of melanoma frequently arising in sun-damaged skin and often first diagnosed in the elderly. Few studies report long-term follow-up. OBJECTIVES: To define characteristics of lentiginous melanoma in situ (LM) and invasive lentiginous melanoma (LMM) in Australian patients managed at a tertiary centre and describe local recurrence or treatment failure rates after long-term follow-up. METHODS: Retrospective single-centre study of LM/LMM patients evaluated between January 2005 and March 2007. Medical and photographic records were reviewed. RESULTS: One hundred two patients were included, with a total of 117 lesions (70 LM and 47 LMM). Seventy-nine were new primary LM/LMM, and 38 were recurrences. Primary cases were mostly pigmented (71%), while 77% of recurrent cases were partially pigmented/light brown or amelanotic. The margins were clinically ill-defined in the majority of cases (64% of primary cases and 94% of recurrent cases). Dermoscopy of the primary LM/LMM showed either classic 'common' melanoma features (33%) or classic LM/LMM features (41%), while 95% of recurrent cases had no features for melanoma or LM/LMM. Primary cases that were initially excised (113, 97%) had mean histopathological clear margins of 4.9 mm (range 0.1-22 mm). The median follow-up time was 7.5 years (95% CI 5.2-10.0) with more than 10-year follow-up in 32% and 5-10 years in 24% of patients. There were 44 (38%) recurrences over the entire follow-up period. Half of the patients who recurred did so within the first 3.8 years after the first treatment. CONCLUSION: LM/LMM often recur late and are clinically subtle; therefore, careful monitoring and long-term follow-up are required.