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
It is important to know that
dermoscopy of pigmented actinic keratoses can reveal the same dermoscopic structures as lentigo maligna melanoma namely rhomboïdal structures and
annular-granular pattern.
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.
