1 Actinic Lentigo

Synonyms are solar lentigo and senile lentigo.

Actinic lentigo (Fig. 7.1) presents as a pigmented macule, with irregular contours, occurring on photo-exposed areas. The color is light brown and homogeneous. It can be single or multiple.

Fig. 7.1
figure 1

Clinical aspect of actinic lentigo

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The IVCM features are as follows (Fig. 7.2a–d):

  • Normal supra-basal epidermis with regular honeycomb pattern (not shown here)

  • Dermo-epidermal junction with increased density of elongated dermal papillae surrounded by a bright monomorphic layer of hyperreflective cells (cordlike rete ridges) (orange arrows) without atypical cells

  • Absence of pagetoid cells

Fig. 7.2
figure 2

IVCM features of actinic lentigo (a–d)

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On optical microscopy the histologic features are as follows (Fig. 7.3e–h):

  • At low magnification (e, f), the epidermis is organized into digitations (due to the lengthening of the epidermal ridges) and basal keratinocytes are hyperpigmented. Melanocytes can be slightly increased in number at the basal layer of the epidermis (orange dotted lines).

  • At high magnification (g, h), melanocytes are regularly distributed at the basal layer of the epidermis without atypia or junctional nest. The epidermal ridges are hyperpigmented in places (black arrows).

Fig. 7.3
figure 3

Histological features of actinic lentigo (e–h). (e, f) ×100 HES. (g, h) ×400 HES

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