The efficacy of 1064-nm Nd: YAG picosecond laser for Becker’s nevus: a retrospective analysis of 49 cases

Abstract

Becker’s nevus (BN) is a benign, unilateral hamartoma characterized by hyperpigmentation and hypertrichosis. Laser and light-based therapies represent the primary treatment modalities. To evaluate the efficacy and safety of the 1064-nm Nd: YAG picosecond laser in the treatment of Becker’s nevus in a Chinese population. This was a retrospective, single-center study of patients with BN treated between March 2021 and August 2025. Efficacy was assessed via photographic evaluation by two independent dermatologists using a 4-point improvement scale. All patients were treated with 1064-nm Nd: YAG picosecond laser (Picoway, Zoom handpiece, Candela, Wayland, MA USA). SPSS 19 (IBM, Armonk, NY, USA) was used for all statistical analyses. 49patients (18 females, 31 males) with BN were included,24 patients presented with hypertrichosis, 25 patients without hypertrichosis. 25 patients without hypertrichosis were only treated with the 1064-nm Nd: YAG picosecond laser, and the number of treatment sessions was positively correlated with the treatment efficacy (r = 0.615, r²=0.378, P < 0.01). There was no correlation between pigmentation improvement and the number of treatment sessions in the 24 patients with Becker’s nevus accompanied by hypertrichosis (r = 0.209, r²=0.044, P>0.05).Adverse events were transient and included pain, erythema, edema, hypopigmentation, and hyperpigmentation. Single-center, retrospective design, lack of a control group. The 1064-nm Nd: YAG picosecond laser is a well-tolerated treatment option for Becker’s nevus, demonstrating moderate efficacy. A significant moderate positive correlation was observed between the number of treatments and clinical outcome in Becker’s nevus without hypertrichosis.

Introduction

Becker’s nevus (BN), also known as Becker’s melanosis or pigmented hairy epidermal nevus, is a benign cutaneous hamartoma presenting as a hyperpigmented patch with or without hypertrichosis [1]. It typically appears in adolescence with a male predominance [1]. While often unilateral, bilateral cases have been reported [2]. BN can be associated with other cutaneous and musculoskeletal anomalies [3–7].

Laser therapy, based on the principle of selective photothermolysis, is the mainstay of treatment for BN [2]. Various lasers, including 755-nm alexandrite, 1064-nm Q-switched Nd: YAG, and diode lasers, have been used with variable success [8]. The 1064-nm Nd: YAG picosecond laser, with its ultrashort pulse duration, theoretically offers enhanced pigment clearance and reduced thermal damage compared to nanosecond-domain lasers [3]. However, data on its use specifically for BN remain limited. This study aims to retrospectively evaluate the efficacy and safety of the 1064-nm Nd: YAG picosecond laser in a cohort of 49 Chinese patients with BN.

Methods

Study design and participants

This retrospective, single-center study was conducted at the Hospital for Skin Diseases, Shandong First Medical University. We reviewed the records of patients with Becker’s nevus (BN) treated between March 2021 and August 2025. A total of 158 patients with Becker’s nevus were identified from patient files. The diagnosis of Becker’s nevus was made independently, according to its typical clinical features and Reflectance Confocal Microscopy images. Exclusion criteria are pregnant and lactating women, photosensitivity, intake of retinoids or photosensitizing medications. All patients were Fitzpatrick skin type Ⅳ. After exclusion of those who were not treated with 1064-nm PicoWay laser, 24 patients presented with hypertrichosis, 25 patients without hypertrichosis were included in the analysis.

Treatment protocol

All patients were treated with 1064-nm Nd: YAG picosecond laser system (PicoWay, Candela) with a pulse duration of 450 ps. The parameters for depigmentation were set at a wavelength of 1064 nm, a fluence of 1.8–2.2 J/cm², and a spot size of 4–5 mm. For patients presenting with hypertrichosis, hair removal was performed concomitantly using a diode laser system (MeDioStar, Asclepion) at a wavelength of 810 nm + 940 nm, a fluence of 16–18 J/cm², and a spot size of 14 mm x 11 mm. The treatment sequence was as follows: hair removal laser treatment was performed in the morning, followed by a 1-hour cold compress. In the afternoon, after confirming the absence of post-laser reactions such as erythema, swelling, warmth, or pain, picosecond laser treatment was administered. A total of 25 patients without hypertrichosis were treated 1–5 sessions (2.80 ± 0.19 sessions, 95%CI 2.40–3.20), at intervals of 12–24 weeks. A total of 24 patients presented with hypertrichosis were treated 1–11 sessions (3.58 ± 0.43 sessions, 95%CI 2.70–4.46), at intervals of 12–24 weeks.

Outcome assessment

Therapeutic efficacy was assessed by two independent, blinded dermatologists. Standardized clinical photographs taken at baseline and before each treatment session were compared. Improvement in pigmentation and hair density was graded using a 4-point scale: 1 (≤ 25% improvement), 2 (26–50%), 3 (51–75%), and 4 (> 75%). After the treatments, adverse reactions were assessed.

Statistical analysis

Statistical analyses were performed using SPSS software (version 19.0, IBM). Descriptive data are presented as mean ± standard error of the mean (SEM) with 95% confidence intervals (CI). The relationship between the number of treatment sessions and clinical improvement was analyzed using Pearson’s correlation coefficient. A P value of less than 0.05 was considered statistically significant.

Results

Patient characteristics

Based on the inclusion criteria, 49 patients were enrolled in the final analysis. The cohort consisted of24 patients presented with hypertrichosis and 25 patients without hypertrichosis All patients had Fitzpatrick skin type IV.

Treatment details

A total of 25 patients without hypertrichosis were treated 1–5 sessions (2.80 ± 0.19 sessions, 95%CI 2.40–3.20), at intervals of 12–24 weeks. A total of 24 patients presented with hypertrichosis were treated 1–11 sessions (3.58 ± 0.43 sessions, 95%CI 2.70–4.46), at intervals of 12–24 weeks.

Efficacy outcomes

Following treatment, 7 of the 25 patients without hypertrichosis (28%) demonstrated greater than 25% improvement in pigmentation (corresponding to Grade 2 or higher, Fig. 1). This included 2 patients (8%) who achieved over 75% improvement (Grade 4). Among the 24 patients with hypertrichosis, 15 (62.5%) showed greater than 25% hair reduction (Grade 2 or higher), with 3 patients (12.5% of this subgroup) reaching over 75% improvement (Grade 4). The remaining patients exhibited minimal improvement (Fig. 1; Table 1).

Fig. 1.

Summary of pigmentation therapeutic Efficacy in BN without hypertrichosis (N = 25)

Table 1.

The Outcome of improvement of BN with hypertrichosis after treatment (N = 24)

	Pigmentation			Hypertrichosis
	Scale	Case	Percentage	Scale	Case	Percentage
Improvement scales	4	0	0	4	3	12.5%
	3	2	8.3%	3	9	37.5%
	2	7	29.1%	2	3	12.5%
	1	15	62.5%	1	9	37.5%
Side Effects	Hyperpigmentation			Hypopigmentation
	Case		Percentage	Case		Percentage
	8		33.3%	2		8.3%

A 26-years-old female with BN on her trunk, whose skin lesions first appeared at the age of 16 years, was observed remarkable improvement following four treatment sessions, which was graded as 3 points (Fig. 2). 25 patients without hypertrichosis were only treated with the 1064-nm Nd: YAG picosecond laser, and the number of treatment sessions was positively correlated with the treatment efficacy (r = 0.615, r²=0.378, P < 0.01). There was no correlation between pigmentation improvement and the number of treatment sessions in the 24 patients with Becker’s nevus accompanied by hypertrichosis (r = 0.209, r²=0.044, P>0.05).

Fig. 2.

Becker’s Nevus on trunk, which was treated only frontal regions. (A) & (B) Before treatment; (C) & (D) 5 months after 4 treatment sessions with 1064-nm Nd: YAG picosecond laser; The patient first noticed the lesion at age 16 years. The overall improvement was graded as 3 points

Adverse events

All adverse events were transient and mild. Immediate post-treatment reactions, including erythema, mild pain, and edema, resolved spontaneously within 36 to 48 h. Post-inflammatory hyperpigmentation occurred in 8 patients (32%) in 25 patients without hypertrichosis, and 8 patients (33.33%) in 24 patients accompanied by hypertrichosis. Hypopigmentation was only foundin 2 patients (8.33%) in patients with hypertrichosis. These pigmentary changes resolved completely within 4 to 6 months after the final treatment session.

Discussion

This retrospective study evaluated the efficacy and safety of the 1064-nm Nd: YAG picosecond laser in the treatment of Becker’s nevus (BN) in a cohort of 49 Chinese patients with Fitzpatrick skin type IV. Our findings indicate that this modality offers moderate improvement in pigmentation, with a favorable safety profile characterized by transient and mild adverse events. Notably, we observed a significant moderate positive correlation between the degree of clinical improvement and the number of treatment sessions in Becker’s nevus without hypertrichosis treated solely with the 1064-nm Nd: YAG picosecond laser.

The proportion of patients achieving > 25% improvement in pigmentation (28%) in our cohort aligns with the reported efficacy of the conventional 1064-nm Q-switched Nd: YAG laser for BN [9–11]. This suggests that despite its theoretical advantages—primarily the generation of potent photomechanical effects with reduced thermal diffusion—the picosecond laser as a monotherapy may not yield superior pigment clearance in BN compared to its nanosecond predecessor. This observation may be attributable to the complex histopathology of BN, which is not merely a pigmentary disorder but a hamartoma involving dermal melanophages, and occasionally smooth muscle and hair follicle hyperplasia [8]. Laser treatment targeting melanin alone may therefore have inherent limitations.

In Becker’s nevus without hypertrichosis treated solely with the 1064‑nm Nd: YAG picosecond laser, we observed a significant moderate positive correlation between the degree of clinical improvement and the number of treatment sessions. The stronger correlation observed in patients without hypertrichosis treated exclusively with the 1064-nm Nd: YAG picosecond laser could be explained as follows. On the one hand, the presence of hypertrichosis (characterized by increased follicular density and diameter) may lead to competitive absorption or scattering of the 1064-nm laser energy, thus reducing the laser’s effectiveness on melanin within the epidermis and dermis. On the other hand, Becker’s nevus accompanied by hypertrichosis might exhibit a more intricate pattern of melanocyte proliferation. Therefore, in the absence of hypertrichosis, the number of treatment sessions showed a stronger positive correlation with clinical improvement.

The safety data from this study reinforce the proposed benefits of the picosecond laser platform. The self-resolving nature of post-inflammatory hyperpigmentation (PIH, 32%) are clinically significant, especially in our Fitzpatrick type IV population which is inherently at higher risk for pigmentary complications. This favorable profile is consistent with the mechanism of picosecond-domain pulses, which favor photomechanical fragmentation of pigment with minimal collateral thermal injury, thereby reducing the risk of epidermal damage and subsequent dyspigmentation [12, 13].

Study limitations and directions for future research

The conclusions of this study must be interpreted within its limitations. The retrospective, single-center design lacks a control group for direct comparison and may be subject to selection bias. The relatively small sample size limits the statistical power to detect meaningful differences in treatment sessions and efficacy between groups. The treatment parameters were not standardized prospectively. Furthermore, efficacy was assessed through subjective physician evaluation of photographs; incorporation of objective measures, such as reflectance confocal microscopy or colorimetry, would strengthen future analyses. Long-term follow-up data are also needed to assess the durability of response and recurrence rates.

Future prospective, controlled studies are warranted to definitively compare the picosecond laser against other established modalities for BN. Research should also explore optimized treatment strategies, such as combination therapies that pair the pigment-specific action of the picosecond laser with modalities capable of addressing the dermal structural components of BN (e.g., fractional lasers). Investigating patient-specific factors—including genetic markers or precise pigment depth—that predict treatment response could pave the way for truly personalized therapeutic protocols.

Conclusions

In summary, the 1064-nm Nd: YAG picosecond laser represents a safe and moderately effective treatment option for Becker’s nevus in patients with darker skin phototypes. The absence of correlation between pigmentation improvement and treatment session number in Becker’s nevus with hypertrichosis challenges the paradigm of simply increasing sessions for better results and emphasizes the importance of developing response-guided treatment algorithms. For Becker’s nevus without hypertrichosis, the treatment outcome may be improved by increasing the number of 1064-nm Nd: YAG picosecond laser treatment sessions. Further research is needed to optimize treatment parameters, evaluate combination regimens, and identify predictors of response to maximize therapeutic outcomes for this condition.

Author contributions

L. M and Y. L contributed equally to this work. L. M and Y. L conceived the study, L. M and Y. L wrote the article, W. S and X. Y collected data, X. G , X. L and G. C followed the cases, H. L supervised the work. L. M and Y. L made the same contribution to the article. All authors have made substantial contribution to the work and have approved the final version of this article.

Funding

The study was funded by Health Development of Shandong Province (202204120385), Health Development of Shandong Province (202320000588), Jinan Science and Technology Bureau (202328052), Shandong Provincial Natural Science Foundation Project (ZR2024MH233).

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Declarations

Ethics approval and consent to participate

This study was conducted in accordance with the 1964 Helsinki Declaration and its later amendments, and was reviewed and approved by Ethics Committee of Hospital for Skin Diseases, Shandong First Medical University. Written informed consent was obtained from all individual participants included in the study.

Competing interests

The authors declare no competing interests.

Clinical trial number

not applicable.