Can You Identify This Asymptomatic Lesion on an Elderly Man’s Temple?

Authors:
Alexander K. C. Leung, MD, and Benjamin Barankin, MD

Citation:
Leung AKC, Barankin B. Can you identify this asymptomatic lesion on an elderly man’s temple? Consultant. 2017;57(12):695-697.

An 81-year-old white man presented with a pigmented lesion in the right temple area. The patient reported that he had first noted the lesion approximately 7 years ago and that it had very slowly increased in size with time. The lesion was asymptomatic. The patient was otherwise in good health. He had worked in construction, and he enjoyed outdoor recreational activities. He had no family or personal history of skin cancer.

Physical examination revealed a flat, dark brown patch with irregular borders, asymmetric shape, and color variegation in the right temple area. Lesions of seborrheic keratosis were present in the adjacent areas and on other parts of the face. The rest of the physical examination findings were unremarkable.

Dermoscopy revealed asymmetric pigmented follicular openings, homogeneous areas with obliteration of follicular openings, gray dots and globules, and rhomboidal structures. Histologic examination of a biopsy specimen showed increased numbers of atypical melanocytes along the dermal-epidermal junction and effacement of rete ridges.

Answer on next page.

Answer: Lentigo Maligna

The patient was informed that he had lentigo maligna and that surgical excision was the treatment of choice, and he agreed to it. The lesion was subsequently excised with appropriate margins. The patient was seen for periodic follow-up, and there was no evidence of recurrence at the 3-year follow-up visit.

LENTIGO MALIGNA OVERVIEW

Lentigo maligna, also known as Hutchinson melanotic freckle, is the most common form of melanoma in situ. It presents as a slow-growing, variably pigmented macule or patch on chronically sun-exposed skin of elderly individuals, most commonly in the head and neck region.¹ The condition was first described by Jonathan Hutchinson in 1891.²

EPIDEMIOLOGY

The incidence in the adult population is estimated to be approximately 13.7 per 100,000 person-years.³ The condition is more common in fair-skinned individuals.^4,5 Lentigo maligna occurs mainly in elderly individuals, with a peak incidence between the seventh and eighth decade of life.^6-8 There is a slight female predominance, presumably because women live longer than men.^7-9

ETIOPATHOGENESIS

UV exposure has an important role, since the lesions of lentigo maligna are more common in sun-exposed areas, in individuals with fair skin, and in individuals with a history of sunburns. Other risk factors include a history of nonmelanoma skin cancers and the tendency to form solar lentigines.^6,10 Lentigo maligna can develop de novo or within an existing solar lentigo.⁶ Patients with lentigo maligna have a higher incidence of tumor protein p53 gene mutations.⁶

HISTOPATHOLOGY

Histologically, there is a proliferation of atypical melanocytes at the basal layer of the epidermis and within the hair follicles, nesting of atypical melanocytes, and effacement of rete ridges.^4,6 Characteristically, there is no dermal invasion.⁴ Changes of chronic sun damage such as epidermal atrophy and degeneration of elastic tissue within the dermis are usually prominent.

CLINICAL MANIFESTATIONS

Clinically, lentigo maligna presents as a solitary, very slow-growing, asymmetric, nonscaly macule or patch with ill-defined, irregular borders and variegated colors (tan-brown to dark black).^6,7,10,11 The surface is absolutely flat and usually smooth. Netlike black pigmentation is often found in this lesion.⁴ Sites of predilection include chronically sun-exposed areas such as the head and neck, with a predilection for the cheek.^9,10 Approximately 86% of all cases occur in the head and neck region.¹¹ Other sites include the upper back, forearms, and legs.^9,10 Markers of actinic damage such as solar elastosis, solar lentigines, and actinic keratosis are often seen in surrounding areas.⁸

DIAGNOSIS

The diagnosis should be suspected based on clinical findings. Assessment of the lesion with dermoscopy and/or, less commonly, reflectance confocal microscopy may aid in the evaluation. Typical dermoscopic findings include asymmetric perifollicular pigmentation, homogeneous areas with obliteration of follicular openings, increased vascular network, red or dark rhomboidal structures, annular-granular pattern, slate gray dots, and slate gray globules.^11-13

Reflectance confocal microscopy provides real-time images of the epidermis and superficial dermis with a cellular resolution approaching that of conventional histology and can be used to define margins of the lesion prior to surgical treatment.^12,14 Based on the reflectance confocal microscopic findings, 2 major criteria denoting the presence of lentigo maligna include nonedged papillae and round, large pagetoid cells greater than 20 µm in size (imparting a score of 2 points each).^9,15 Four minor criteria include 3 or more atypical cells at the dermal-epidermal junction, follicular localization of atypical cells, nucleated cells within the dermal papillae (each imparting a score of 1 point), and a broadened honeycomb pattern (imparting a score of –1 point).^9,15 A score of 2 or more points is suggestive of lentigo maligna with a sensitivity of 85% and a specificity of 76%.^9,15

Biopsy remains the gold standard for diagnosis and should be considered if the diagnosis is in doubt or when dermoscopic examination discloses a gray color.^8,12,13

DIFFERENTIAL DIAGNOSIS

A melanoma should be suspected in a pigmented skin lesion that displays features of the ABCDE characteristics. These features include asymmetry (one half of the lesion does not match the other in shape and color); borders that are irregular and/or indistinct; color variegation (mottled with different shades); diameter greater than 6 mm; and evolution over time with progressive lesional enlargement and/or color and/or symptom changes.

Lentigo maligna melanoma is a subset of melanoma arising in chronically sun-exposed skin of the head and neck, seen most frequently in the elderly white population. The condition mimics lentigo maligna very closely. In contrast to lentigo maligna, the atypical melanocytes are not confined to the epidermis.¹ Rather, they are arrayed along the epidermal-dermal junction in a lentiginous pattern and form nests along the epidermal-dermal junction and nodules or fascicles in the dermis. Clinically, the lesion of lentigo maligna melanoma is darker and more variegated in color, has sharper borders, and has elevated areas compared with that of lentigo maligna.

Other differential diagnoses include solar lentigo, pigmented actinic keratosis, seborrheic keratosis, actinic keratosis, lichen planus-like keratosis, dysplastic nevus, Bowen disease, pigmented basal cell carcinoma, and melanocytic nevus.^1,12

COMPLICATIONS AND PROGNOSIS

The lesion can be cosmetically unsightly and an esthetic concern if it occurs in an exposed area. Lentigo maligna can undergo malignant transformation to lentigo maligna melanoma. An increase in dark pigmentation, color variegation, development of an elevated area, an increase in size, and an increase in border irregularity suggest malignant transformation.¹⁰

If left untreated, the lifetime risk of progression to lentigo maligna melanoma ranges from 5% to 20%.¹⁰ Lentigo maligna has the metastatic potential of malignant melanoma.¹⁰ Lentigo maligna is notorious for recurrence even after apparently adequate treatment.^16,17

PREVENTION

Because UV exposure has an important role in the pathogenesis, sun avoidance during hours of peak UV intensity (11 am to 4 pm) and the use of broad-spectrum sunscreens and protective attire, including sunglasses and sun-shielding apparel (eg, wide-brimmed hats) when outdoors cannot be overemphasized.

MANAGEMENT

Surgical excision is the treatment of choice.^6,17,18 This can include local excision with a wide safety margin (> 5 mm margin as advocated by current guidelines); a staged excision with rush paraffin-embedded, permanent sections; and Mohs micrographic surgery.^9,18 Mohs micrographic surgery has a 5-year recurrence rate of approximately 1.9%, whereas wide surgical excision has a 5-year recurrence rate of at least 5.9%.¹⁶ Surgical excision has the benefit of allowing histopathologic analysis and assessment of margin clearance.¹⁷

Other treatment options for patients unfit for or unwilling to undergo surgery include radiation therapy, laser therapy, and topical imiquimod with or without topical tazarotene.^16,17,19,20 Laser therapy has a high recurrence rate and is least desired.¹⁷ Regardless of the kind of treatment, affected patients must be monitored for recurrence.¹⁰

Alexander K. C. Leung, MD, is clinical professor of pediatrics at the University of Calgary and a pediatric consultant at the Alberta Children’s Hospital in Calgary, Alberta, Canada.

Benjamin Barankin, MD, is a dermatologist and the medical director and founder of the Toronto Dermatology Centre in Toronto, Ontario, Canada.

REFERENCES:

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