Slowly enlarging pigmented patch on the cheek

Lentigo maligna, 25 mm, completely excised by staged technique

Learning points

• Facial dermoscopy features of LM (annular-granular pattern, asymmetric pigmented follicular openings, rhomboid structures, grey-blue pseudonetwork) differ from trunk / limb dermoscopy because of thin epidermis and prominent follicles.
• Pigmented actinic keratosis and solar lentigo are the main clinical and dermoscopic mimics — the 'four-point' facial LM algorithm helps but inter-rater agreement is moderate. Biopsy when in doubt.
• Mapping (multiple punch) or scouting biopsy is preferable to a single small punch when LM is suspected on a clinically large lesion — preserves the option of staged excision and avoids sampling error.
• NICE NG14 in-situ margin: 5–10 mm for lentigo maligna where anatomy permits; the lentigo maligna variant frequently extends sub-clinically beyond visible margins and often warrants staged excision ('slow Mohs' / square procedure with permanent-section margins) or Mohs with immunostains (MART-1 / SOX-10).
• Topical imiquimod is an option in selected non-surgical cases (poor surgical candidates, very large lesion) but recurrence rates are higher.
• Periocular and central facial reconstruction principles — subunit-based, cervicofacial advancement or paramedian forehead flap may be required for larger defects.