Lentigo Maligna_0114 Derm Clinic 2
A man, aged 67 years, presented for a full skin examination. No personal history of skin cancer or family history of malignant melanoma was reported. As a teenager and young adult the man worked as a lifeguard and used no sun protection. For the past 20 years, he has worked as a contractor, spending most of the day outdoors without any sun protection.
The patient noted that a brown spot on his nose had been slowly getting larger over the past 10 years. Physical exam revealed a 9-mm × 11-mm brown patch on the right nasal dorsum with asymmetry, uneven borders, and color variation.
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Dermoscopic examination of the man’s nasal lesion revealed an asymmetric reticular pigment network with gray circles, as well as varying perifollicular hyperpigmentation. A shave biopsy was performed, and histologic exam confirmed the suspected diagnosis of lentigo maligna, also known as lentiginous melanoma on sun-damaged skin or Hutchinson melanotic freckle. Lentigo maligna is a precursor to lentigo maligna melanoma, a form of melanoma unique to older individuals with heavily sun-damaged skin that appears specifically in areas of chronic sun exposure.
Physical characteristics of lentigo maligna include:1
- Large size (typically >6 mm and often several cm in diameter at the time of diagnosis)
- Irregular borders
- Varied pigmentation (may include light brown, tan, dark brown, pink, red, or white)
- Smooth surface
After five to 20 years of peripheral growth, if undetected and untreated, the lentigo maligna lesion may grow vertically, and an invasive melanoma develops. In rare cases, transformation to invasive melanoma can occur more rapidly, even over the course of only a few months.
Persons most at risk for lentigo maligna are those with a history of excess UV radiation exposure and signs of actinic damage. Incidence peaks between age 65 years and age 80 years. Persons with fair skin, multiple melanocytic nevi, a history of severe sunburn, occupational exposure to sun, and a family history of melanoma are at heightened risk. The incidence of lentigo maligna is highest in Hawaii, whereas incidence of melanoma is highest among those who have lived in Australia for many years.
Lentigo maligna typically starts as a tan, brown, or black macule that slowly expands peripherally over the course of many years. As it progresses, the lesion demonstrates more atypical features, such as uneven pigmentation and irregular borders. The most commons sites of lentigo maligna are the head and neck. Interestingly, lentigo maligna is more commonly seen on the left side of patients who have spent a great deal of time driving, and it appears more commonly on the right side in those who were most often passengers in the front seat.
Physical examination of suspicious lesions should include use of the ABCDE rule.2 Inspect for Asymmetry, irregular Border, Color variegation, and larger Diameter, and inquire about history of Enlargement. Clinical diagnosis of lentigo is typically challenging, as lesions are frequently buried among benign lentigines, nevi, actinic keratoses, and seborrheic keratoses.
Dermoscopy may aid in the diagnosis of lentigo maligna and decrease unnecessary biopsies.3 Four criteria often noted in lesions of lentigo maligna are asymmetric pigmented follicular openings, rhomboidal structures, annular-granular structures, and gray pseudo-network.4
Biopsy of the suspicious lesion is necessary to confirm the diagnosis. Although excisional biopsy is generally preferred for suspected melanomas, because suspected lentigo maligna lesions are usually on the face, results are often cosmetically unacceptable. Therefore, a deeper incisional shave biopsy is reasonable. Studies have shown that incisional biopsies have no negative effect on mortality.5
Beyond biopsy and full skin examination, such additional workup as x-ray and lymph-node biopsy is usually reserved for patients with invasive melanomas.
Early surgical excision is the preferred treatment of lentigo maligna. For in situ melanomas, the National Comprehensive Cancer Network practice guidelines recommend a margin of 0.5 cm.6 However, in lentigo maligna melanoma, subclinical extension of the in situ tumor often extends beyond 0.5cm, with disproportionate expansion being common.
In such scenarios, Mohs micrographic surgery or a staged excision may be preferred and appear to offer higher cure rates.7 Staged excision involves initial excision with narrower margins, often guided by the use of a Wood’s lamp. Permanent sections are then examined by a dermatopathologist, usually within 24 hours. Further excisions are performed based on the histologic findings.
In patients who are poor surgical candidates, other treatment considerations may include the immune response modifier imiquimod (Aldara, Zyclara), cryotherapy, or radiation.8,9 None of these options are typically ideal as solo treatment. Close evaluation of patients undergoing imiquimod therapy is essential and should include posttherapy histopathologic investigation.10
Prognosis for patients with lentigo maligna melanoma is similar to prognosis for patients with malignant melanoma in situ (i.e., 95%-100% five-year survival rate).11
Patients with a history of LM should be educated to perform monthly skin and lymph-node self-examinations. Any new or changing lesions should be evaluated by a dermatology provider. Clinical full-skin examinations should be performed every six months. Patients should be reminded to practice strict sun protection with the use of sunscreens and protective clothing.
The man describe in this case underwent a shave biopsy of the suspicious lesion on his nose. Hematoxylin and eosin stains confirmed the diagnosis of lentigo maligna. The patient was referred to a surgical oncologist for staged excision of the lesion. After the margins were deemed clear of lentigo maligna melanoma, the defect was closed by a plastic surgeon.
Three months later, the patient returned with a wonderful cosmetic outcome and no evidence of recurrence of the previous lentigo maligna. A full-skin examination revealed no suspicious lesions elsewhere.
Esther Stern, NP-C, is a family nurse practitioner at Advanced Dermatology & Skin Surgery, P.C., in Lakewood, N.J.
- Kallini JR, Jain SK, Khachemoune A. Lentigo maligna: review of salient characteristics and management. Am J Clin Dermatol. 2013;14:473-480.
- Shenenberger DW. Cutaneous malignant melanoma: a primary care perspective. Am Fam Physician. 2012;85:161-168. Available at www.aafp.org/afp/2012/0115/p161.html.
- Stante M, Giorgi V, Stanganelli I, et al. Dermoscopy for early detection of facial lentigo maligna. Br J Dermatol. 2005;152:361-364.
- Tanaka M, Sawada M, Kobayashi K. Key points in dermoscopic differentiation between lentigo maligna and solar lentigo. J Dermatol. 2011;38:53-58.
- Bong JL, Herd RM, Hunter JA. Incisional biopsy and melanoma prognosis. J Am Acad Dermatol. 2002;46:690-694.
- Coit DG, Andtbacka R, Bichakjian CK, et al. Melanoma. J Natl Compr Canc Netw. 2009;7:250-275. Available at www.jnccn.org/content/7/3/250.long.
- Clark GS, Pappas-Politis EC, Cherpelis BS, et al. Surgical management of melanoma in situ on chronically sun-damaged skin. Cancer Control. 2008;15:216-224.
- Wong JG, Toole JW, Demers AA, et al. Topical 5% imiquimod in the treatment of lentigo maligna. J Cutan Med Surg. 2012;16:245-249.
- McLeod M, Choudhary S, Giannakakis G, Nouri K. Surgical treatments for lentigo maligna: a review. Dermatol Surg. 2011;37:1210-1228.
- Wolf IH, Cerroni L, Kodama K, Kerl H. Treatment of lentigo maligna (melanoma in situ) with the immune response modifier imiquimod. Arch Dermatol. 2005;141:510-514. Available at archderm.jamanetwork.com/article.aspx?articleid=393575.
- Koh HK, Michalik E, Sober AJ, et al. Lentigo maligna melanoma has no better prognosis than other types of melanoma. J Clin Oncol. 1984;2:994-1001.
All electronic documents accessed December 15, 2013.