Derm Dx: Irregular, discolored brown spot on the cheek

Histopathological examination confirmed the diagnosis of lentigo maligna melanoma, a potentially invasive form of melanoma that comprises about 4 to 15% of these neoplasms. 1,2 Lentigo maligna melanoma occurs most commonly in elderly individuals above the age of 70.3 The...

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Histopathological examination confirmed the diagnosis of lentigo maligna melanoma, a potentially invasive form of melanoma that comprises about 4 to 15% of these neoplasms. ^1,2

Lentigo maligna melanoma occurs most commonly in elderly individuals above the age of 70.³ The major risk factor for the development of this condition is chronic outdoor sun exposure and sun damaged skin. Thus, lentigo maligna melanoma typically presents on sun damaged sites, particularly areas on the head and neck.

The precursor to lentigo maligna melanoma is called lentigo maligna or Hutchinson melanotic freckle.  This lesion presents as a macule or patch which is characterized by irregular shades of tan, brown, or black pigmentation. Although most remain benign, a small percentage of Hutchinson melanotic freckles evolve into melanomas with the transition often characterized by the appearance of raised, darkened papules.

Clinical diagnosis of lentigo malignant melanoma may be challenging since it gradually arises from a benign precursor and may resemble other benign lesions such as a thin seborrheic keratosis and solar lentigo.  Diagnosis is invariably made through excisional or punch biopsy of the lesion.  Histologically, the lesion appears as melanocytic hyperplasia at the dermo-epidermal junction with underlying sun damage.⁴

The ideal treatment of lentigo maligna melanoma is somewhat controversial.⁵ Standard excision has a high recurrence rate which may be the result of ill-defined borders, large size and desire to minimize cosmetic facial disfigurement.

Staged excision and Mohs surgery result in higher cure rates but entail greater expense and surgical skill.^6,7 Radiation therapy has a variable success rate and may produce satisfactory cosmesis.⁸ Successful treatment has also been reported with the topical immune  modulator imiquimod.⁹

Regardless of therapy, all patients should be encouraged to avoid sun exposure or utilize broad spectrum sunscreens and undergo monitoring to detect recurrence on a routine basis.

Megha D. Patel, is a student at the Commonwealth Medical College, Scranton, Pennsylvania.

Stephen Schleicher, MD, is an associate professor of Medicine at the Commonwealth Medical College and an Adjunct Assistant Professor of Dermatology at the University of Pennsylvania Medical College. He practices dermatology in Hazleton, Pennsylvania.

References

1. Clark WH Jr., Elder DE, Van Horn M. Hum Pathol. 1986;17:443-50.
2. Langley RGB, Flotte TJ, Sober AJ. (1998.) Clinical characteristics. In: Balch CMHA, Sober AJ, Soong S, (Eds.), Cutaneous melanoma. (pp. 81-101). St. Louis: Quality Medical Publishing Inc.
3. Weinstock MA, Sober AJ. Br J Dermatol. 1987; 16: 303-10.
4. Clark WH Jr, Bernardino EA. Cancer Res. 1969;29:705-27.
5. Tzellos, T; Kyrgidis, A; Mocellin, S; Chan, A; Pilati, P; Apalla, Z. Interventions for melanoma in situ, including lentigo maligna. The Cochrane database of systematic reviews 12: CD010308. PMID 25526608
6. Bene NI, Healy C, Coldiron BM.  Dermatol Surg. 2008;34(5):660-664
7. Bub JL, Berg D, Slee A, Odland PB. Arch Dermatol. 2004;140(5):552-558
8. Schmid-Wendtner, M., Brunner, B., Konz, B., Kaudewitz, P., Wendtner, C., Peter, R. et al. J Am Acad Dermatol. 2000; 43: 477-482.
9. Buettiker UV, Yawalkar NY, Braathen LR, Hunger RE. Arch Dermatol. 2008;144(7):943-5.