Table 1.

Median and quartiles (p25–p75) of the percentage of melanin in the basal layer and in the upper dermis, dendrite count, and melanin granulation in the histological sections of skin with melasma and normal adjacent skin, before and after (pre and post) irradiation with UVB, UVA, and visible light (VL). Data analysis adjusted by phototype.

Irradiation	Variable	Facial melasma			Normal adjacent skin			p (time × group)**
		Pre	Post	p*	Pre	Post	p*
UVB	MelBasal	64 (60–65)	65 (65–68)	<0.01	54 (53–56)	56 (55–62)	<0.01	0.09
	MelUD	44 (30–77)	45 (38–97)	0.24	44 (32–71)	67 (41–87)	0.04	0.84
	Dendrites	6 (2–8)	10 (8–18)	<0.01	6 (3–14)	11 (7–16)	0.05	0.59
	GranMelanos	2.0 (1.5–2.1)	1.6 (1.3–2.0)	0.11	1.9 (1.4–2.0)	1.9 (1.6–2.0)	0.80	0.98
UVA	MelBasal	62 (54–66)	70 (57–72)	<0.01	56 (49–61)	57 (50–63)	<0.01	0.06
	MelUD	41 (18–88)	86 (36–144)	0.05	45 (27–90)	74 (34–204)	0.50	0.88
	Dendrites	8 (4–11)	8 (2–22)	0.92	3 (2–5)	5 (3–9)	0.26	0.53
	GranMelanos	1.0 (1.0–1.8)	2.0 (1.8–2.1)	0.05	1.3 (1.3–2.0)	1.3 (1.1–1.9)	0.34	0.03
Visible light	MelBasal	73 (59–74)	75 (69–80)	<0.01	64 (56–66)	70 (61–75)	<0.01	0.09
	MelUD	62 (54–72)	52 (45–83)	0.11	66 (59–83)	75 (53–127)	0.34	0.21
	Dendrites	2 (1–4)	4 (2–14)	0.11	1 (0–3)	4 (1–5)	0.06	0.38
	GranMelanos	1.4 (1.0–2.0)	1.5 (1.0–2.3)	0.11	1.5 (1.0–2.0)	1.5 (1.0–2.0)	0.80	0.98

MelBasal, percentage of melanin in the basal layer of the epidermis; MelUD, percentage of melanin in the upper dermis (×100); GranMelanos: granulation score of melanosomes of the epidermis (1+, fine granulation; 2+, moderate granulation; 3+, coarse granulation), mean of four fields.

^*p-value, pre vs. post (adjusted by phototype).

^**p-value, melasma vs. normal adjacent skin depending on the response to irradiation (adjusted by phototype).