A 67-year-old man noted that a brown spot on his face was growing larger and darker (Figure 175-1). Dermoscopy was performed, and polygonal lines and rhomboidal structures were seen around the follicular openings (Figure 175-2). A broad shave biopsy of the whole lesion showed lentigo maligna (LM) (melanoma in situ). The patient had a long history of multiple skin cancers including multiple thin melanomas on his back. He also had cardiac problems and was on Coumadin. The options for treatment were presented, and he chose to try topical imiquimod. He was instructed to apply the imiquimod daily to the involved area and was seen monthly. After 2 months it was obvious that he was having an exuberant inflammatory response to the imiquimod as desired (Figure 175-3). He completed the 3-month course. Three months after completion his face appeared completely clear (Figure 175-4) clinically and dermoscopically.
Lentigo maligna (melanoma in situ) on the face of a 67-year-old man. (Reproduced with permission from Richard P. Usatine, MD.)
Dermoscopy of lentigo maligna on the cheek showing polygonal lines that make rhomboid structures around the follicular openings. (Reproduced with permission from Richard P. Usatine, MD.)
An exuberant inflammatory reaction to imiquimod applied daily to any remaining lentigo maligna on the cheek after a broad saucerization of the lesion. (Reproduced with permission from Richard P. Usatine, MD.)
The face is clinically and dermoscopically clear of lentigo maligna 3 months after completing the treatment with imiquimod. Through years of follow-up the patient never had a clinical relapse of this LM. (Reproduced with permission from Richard P. Usatine, MD.)
Lentigo maligna is a subtype of melanoma in situ that begins as a tan-brown macule, most often on sun-damaged areas of fair-skinned older individuals.
Hutchinson melanotic freckle.
The incidence of LM is directly related to sun exposure.
Generally, patients with LM are older than age 40 years and fair skinned, with a peak incidence between the ages of 65 and 80.1
LM may represent as much as 25% of all melanomas on the head and neck.2
Melanoma in situ (of all types) is increasing at up to 10% per year, faster than any other cancer.3
ETIOLOGY AND PATHOPHYSIOLOGY