Clinical findings are not helpful in detecting lentigo maligna melanoma in patients with biopsy‐proven lentigo maligna

BACKGROUND: Lentigo maligna (LM) based on biopsy material might be lentigo maligna melanoma (LMM) after excision. OBJECTIVES: Investigate whether clinical and dermoscopic mapping increases the detection rate of LMM when investigating staged excision specimens of biopsy proven LM. METHODS: Patients with biopsy‐proven LM planned for staged excision were included. Using clinical inspection and dermoscopy, spots suspicious for LMM were marked. After the excision, needles were placed at the marked spots. Histological examination using vertical sections was done at the needles followed by the standard amount of vertical sections. RESULTS: In 28 of the 58 biopsy‐proven LM, there was clinical suspicion of LMM, only 3 of these 28 cases were upgraded into LMM. These three cases showed LMM in other sections, whereas only 1 case showed LMM around the needle. Within the group without clinical suspicion of LMM, 2 cases were LMM. Biopsy‐proven LM were in fact LMM in 8.6% of the cases and were found without the clinical guidance of the dermatologist. CONCLUSIONS: 8.6% of the biopsy‐proven LM were LMM after complete histological examination. In this study, the dermatologist was not able to increase the detection rate of LMM by using clinical and dermoscopic mapping.