A 74-year-old woman consulted for this pigmented lesion on her left cheek. She had been operated on 6 years before for a lentigo maligna melanoma. The excision was complete.
A pigmentation recurred slowly 4 years after the excision.
Dermoscopy revealed a dark brown annular-granular pattern.
A biopsy confirmed the diagnosis of recurrence of the lentigo maligna melanoma and the patient was operated on for a second time.
The other possible dermoscopic signs of a lentigo maligna melanoma are:
- asymmetric follicular openings
- rhomboïdal structures
- homogenous areas
- milky red areas
The 3 main differential diagnoses of lentigo maligna melanoma are:
- actinic lentigo and flat seborrheic keratosis: pseudo-network, milia-like cysts, finger-print like structures, moth-eaten border or jelly-like edge (jelly sign)
- pigmented actinic keratosis: usually presence of surface scale, broken-up pseudonetwork
- pigmented basal cell carcinoma: blue-gray ovoïd nests, blue gray globules, leaf-like areas, spoke-wheel structures, ulcerations, arborizing vessels
In this cases dermoscopy is not sufficient to allow an accurate discrimination between a pigmented AK and a LMM, but dermoscopy helps to find the correct area for biopsy, for example the darker area.