Dermoscopic Changes of Melanocytic Nevi after Psoralen-Ultraviolet A and Narrow-Band Ultraviolet B Phototherapy.

BACKGROUND: Phototherapy may alter the morphologic features of melanocytic nevi. Dermoscopy is a non-invasive method for evaluation of skin lesions, specifically melanocytic nevi. AIMS AND
OBJECTIVES: This study was designed to evaluate the effects of narrowband ultraviolet B (NB-UVB) and psoralen-ultraviolet A (PUVA) therapy on the dermoscopic features of nevi.
METHODS: A total of 74 melanocytic nevi were randomly selected from 20 patients. Out of those, 54 nevi received NB-UVB, while 20 received PUVA. 50% of the nevi in each group were exposed to radiation, while the remaining nevi were covered with an opaque tape. All nevi were demoscopically evaluated before and after 30 or 60 sessions of phototherapy.
RESULTS: Overall demoscopic changes were observed in 34/37 (91.8%) of the uncovered nevi compared to 16/37 (43.2%) of the covered nevi (P value 0.0001). The most common changes were new dot/globule formation (62.1%), darkening (32.4%), nevus enlargement (27%), and patchy pigmentation (18.8%). Compared to NB-UVB, dermoscopic changes were more frequent in both covered and uncovered nevi of the PUVA group. (P values 0.041 and 0.0172, respectively). New dot/globule formation was observed more frequently in the covered and uncovered nevi of PUVA group.
CONCLUSION: PUVA and NB-UVB induce dermoscopic changes in the majority of the irradiated nevi. However, PUVA is associated with higher frequency of dermoscopic changes in both covered and uncovered nevi.

What was known?

Melanocytic nevi exposed to ultraviolet light undergo morphologic changes as a result of increase in melanocyte density as well as melanin synthesis. Dermoscopic changes including increase in size and number of nevi and size of globules as well as general darkening may occur after therapeutic doses of NB-UVB or PUVA.

Introduction

Narrowband ultraviolet B (NB-UVB) and psoralen plus UVA (PUVA) have long been used as effective treatment modalities for a broad range of skin diseases. Nevertheless, ultraviolet radiation (UVR) has been recognized as the main environmental cause of skin cancers through different mechanisms including direct DNA damage, suppression of cutaneuos cell-mediated immunity, and the stimulation of melanocyte proliferation.[1] The specific wavelengths responsible for inducing melanoma are unknown. PUVA therapy leads to the formation of PUVA lentigines consisting of atypical melanocytes with increased melanocytic activity.[2] PUVA has also been associated with increased risk of malignant melanoma.[34] However, this finding has not been confirmed in another study.[5] Although animal studies suggest that UVB may be responsible for the induction of cutaneous melanoma,[67] follow-up studies have not found an increased risk of melanoma after therapeutic doses of NB-UVB or broad band UVB.[89] Therefore, studies investigating the effects of UVA and UVB radiation on morphologic and histopathological alterations in melanocytic nevi may help elucidate the mechanisms inovolved in the interaction of UVR and human melanocytes.

Dermoscopy is a non-invasive method for evaluation of a variety of colors and structures of the epidermis, the dermoepidermal junction, and the papillary dermis not visible to the naked eye. These specific dermoscopic patterns are closely related to the histopathology of the pigmented lesion and provide a valuable aid in diagnosing the benign or malignant nature of the lesion. During the past two decades, attempts have been made to explore the morphologic alterations in melanocytic nevi induced by UV exposure.[1011121314151617] Since the morphologic appearance of a nevus in individuals undergoing phototherapy could raise suspicion of a melanoma, understanding the different dermoscopic patterns of nevi after therapeutic UVA and UVB is crucial to identify the true high risk nevi that require an excisional biopsy to rule out melanoma and to avoid unnecessary procedures.

To the best of our knowledge, the previous studies tended to focus mainly on the effects of sunlight, broad-band phototherapy, and single dose exposure, while there is still limited evidence on the impacts of either NB-UVB or PUVA therapy and their differences on dermoscopic appearance of melanocytic nevi, particularly in the therapeutic doses.[141518]

The present study was designed to evaluate the effects of therapeutic doses of NB-UVB and PUVA therapy on the dermoscopic features of acquired melanocytic nevi. The dermoscopic changes induced by NB-UVB or PUVA in the exposed and non-exposed melanocytic nevi have been compared.

Materials and Methods

This prospective interventional study was approved by the Tehran University of Medical Sciences Board of Ethics and was conducted at Razi hospital from October 2008 to December 2009. The study population was randomly selected from patients who were referred by the attending dermatologist to receive either NB-UVB or PUVA therapy for dermatologic disorders. The decision for phototherapy was made independently from this study. Individuals with personal or family history of melanoma, atypical nevus syndrome, and those who had previously received any phototherapy treatment were excluded. All patients gave informed consent and were advised to avoid sun exposure during the treatment. The study patients were clinically and dermoscopically examined by an experienced dermatologist. (Dermoscopy device: microDERM D120, Visiomed, Germany). At least two morphologically similar melanocytic nevi per patient (diameter < 5 mm) without clinical or dermoscopic features of atypia were selected. One nevus was randomly selected to remain exposed during the entire phototherapy sessions while the other nevus was covered with an opaque tape.

PUVA treatment was given using Waldmann UVA 200 Phototherapy Unit (Germany) two hours after oral ingestion of 0.6 mg/kg of 8-methoxypsoralen. The initial radiation dose was determined based on the patient's skin phototype. The patients received three treatments per week with incrementing dose as tolerated. NB-UVB was given using a Waldmann UV 5040BL UV unit following a three sessions per week protocol.

The covered and uncovered nevi were demoscopically evaluated at 30th (n = 5 patients) or 60th (n = 15 patients) sessions of therapy depending on the underlying disease and the scheduled phototherapy protocol. The baseline and post-radiation digital dermoscopy images were evaluated by two independent and blinded investigators and were compared in terms of color, maximal diameter, and structural changes.

Statistical analysis was conducted using Statistical Package for the Social Sciences (SPSS, IBM co.) version 17.00. The Chi-square analysis and Fisher's exact test were applied. The statistical significance was set at P < 0.05.

Results

Patient data

In total, 74 melanocytic nevi of 20 patients, 12 male (60%), with a mean age of 35 years were studied. The patients received phototherapy for various skin conditions including mycosis fugoides (9), Vitiligo (6), psoriasis (3), morphea (1), lichen planus (1). 54 nevi received NB-UVB while 20 received PUVA. 50% of the nevi in each group were exposed to radiation while the remaining nevi were covered. Table 1 shows the anatomical location and type of the studied nevi.

Table 1

Anatomical location and type of the studied nevi

Effect of phototherapy on dermoscopic feature of nevi

Demoscopic changes after phototherapy with either modalities were observed in 34/37 (91.8%) of the exposed nevi compared with 16/37 (43.2%) of the covered nevi (P value 0.0001). The most common dermoscopic changes were new dot/globule formation (62.1%) [Figures 1 and 2], overall darkening (32.4%) [Figure 3], increase in the nevus size (27%) [Figure 4], and patchy pigmentation (18.8%). The enlarging nevi showed significant increase in the maximal diameter form 3.9 mm to 4.6 mm. All these changes were significantly more frequent among the exposed nevi than the covered nevi [Table 2]. Dermoscopic changes were not significantly influenced by patients’ age, sex, skin phototype, or anatomical location of the nevi (P > 0.05).

Figure 1

Dermoscopy of melanocytic nevus before (a) and after (b) phototherapy. New dot and globule formation is seen

Figure 2

Dermoscopy of melanocytic nevus before (a) and after (b) phototherapy. New dot formation and patchy pigmentatiom is seen

Figure 3

Dermoscopy of melanocytic nevus before (a) and after (b) phototherapy. Overall increase in pigmentation is seen

Figure 4

Dermoscopy of melanocytic nevus before (a) and after (b) phototherapy. Increase in nevus size is seen

Table 2

Changes in the dermoscopic features of exposed and covered melanocytic nevi after receiving UV radiation

Differences between NB-UVB and PUVA-treated nevi

The particular effects of PUVA and NB-UVB phototherapy were compared. The prevalence of overall dermoscopic changes was significantly higher in the PUVA-exposed nevi (100% for PUVA, 88.8% for NB-UVB, P value 0.041). No differences were found between the effects of the two types of UV therapy regarding the frequency of enlarging nevi and the amount of hyperpigmentation. However, new dot-globule formation was noted in all nevi (100%) exposed to PUVA compared to only 48.1% in the NB-UVB group (P value 0.0056) [Table 3].

Table 3

Comparison of the dermoscopic features of exposed and covered nevi in NB-UVB and PUVA-treated patients

Among covered nevi, dermoscpoic changes were also more frequently observed in the PUVA-treated patients [7/10 (70%) for PUVA, 2/27 (33.3%) for NB-UVB, P value 0.0172]. In particular, new dot/globule formation was significantly more frequent in the covered nevi of PUVA-treated patients (P value 0.0092) [Table 3].

Discussion

UV light provokes the secretion of Pro-opiomelanocortin (POMC)-derived peptides including melanocyte-stimulating hormone from exposed skin cells and enhances the proliferative activity by up-regulating the expression of their corresponding receptors.[19] Therefore, the morphologic changes in the irradiated nevi could be best explained by the increase in melanocyte density as well as melanin synthesis.[1320] The induced changes in UV irradiated nevi tend to regress after the cessation of radiation indicating that the increase in size and changes in the dermsocopic feature are less likely to induce or promote the development of melanoma within a melanocytic nevi.[111315]

In this study we showed that 91.8% of the nevi openly exposed to either NB-UVB or PUVA undergo dermoscopic alteration. New dot/globule formation (62.1%) was the most common dermoscopic change in our study followed by overall darkening (32.4%), increase in the nevus size (27%), and patchy pigmentation (18.8%). These dermoscopic alterations are in accordance with other studies; Dervis et al. observed a significant increase in size and number and size of globules as well as general darkening in study of 28 melanocytic nevi after PUVA treatment.[18] Study by Manganoni et al. showed that nevus enlargement, increase in number and size of globules/dots, and overall darkening occurs after 4 weeks of UVB or UVA in the melanocytic nevi of healthy individuals.[14] Widening of the pigment network and formation of branched streaks were also noted in these studies, however, we found no changes in the pigment structure or streaks. Pullmann et al. observed an increase in the nevi size and overall pigmentation after photochemotherapy.[21]

Pigmented globules histologically correspond to either melanocyte nests at the dermoepidermal junction or melanin storage in melanophages of the papillary dermis while pigmented dots are representative of focal accumulations of free melanin or highly pigmented melanocytes in the epidermis or dermis. Therefore, the new dot/globule formation, the most commonly encountered dermoscopic alteration of melanocytic nevi after phototherapy, corresponds to the increase in melanin synthesis and/or melanocyte proliferation. Importantly, none of the dermoscopic patterns generally associated with malignant melanoma including asymmetry, atypical dot/globule, blue-white veil, pseudopods, radial streaming, atypical network, irregular streaks, or regression structures were noted in the studied nevi. Phototherapists should be familiar with the expected dermoscopic changes of nevi after PUVA and NB-UVB when following upon melanocytic nevi. Emergence of any of the above mentioned high-risk patterns in malonocytic nevi exposed to phototherapy should not be considered a natural consequence of phototherapy and histological evaluation of the suspicious nevi is mandatory.

In this study, the effects of NB-UVB and PUVA on the dermoscopic features of the uncovered nevi were compared; we observed that the PUVA-treated nevi were more likely to show morphologic changes (particularly new dot/globule formation) compared to their NB-UVB irradiated counterparts. In a similar study, Karaarslan et al. compared the effect of NB-UVB and PUVA therapy on melanocytic nevi and detected more pronounced and sustained changes in NB-UVB irradiated nevi, suggesting that NB-UVB may have a higher potential to induce melanocytic proliferation. In addition, they observed that increase in the number of dots or globules were exclusively seen in the NB-UVB-treated nevi.[15] However, according to our results, these changes were not only seen in the PUVA exposed nevi, they were in fact more frequent in this group.

Induction of dermoscopic alteration in the covered nevi of both groups, especially in the PUVA-treated patients, is another notable finding of this study. Animal studies demonstrated that UVR may result in the proliferation of melanocytes in both shielded and unshielded areas.[22] This concept was further supported in human studies postulating the theory that a certain mitosis stimulating factor originated from the exposed skin cells might spread through a paracrine pathway and consequently alter the histopathologic and morphologic appearance of protected nevi.[23] A wide variety of paracrine factors including mediators and cytokines such as POMC, endothelin-1 (ET-1), stem cell factor (SCF), interleukin-1 (IL-1), interferon-gamma (IFN-g), and granulocyte-macrophage colony-stimulating factor (GM-CSF) have been identified.[202425]

The significantly higher frequency of dermoscpoic changes in the covered nevi of the PUVA group as compared with NB-UVB group suggests that physical protection against PUVA may not be as effective as against NB-UVB radiation. This finding may be due to the effect of psoralen photochemistry or specific melanocytic target and distinct photobiological activity induced by different spectrums of UV radiation specifically the paracrine and endocrine signals. However, this concept needs to be validated and further elucidated by future molecular and histopathological studies.

The reversibility of the UV-induced dermoscopic changes and follow-up of the patients was not assessed in this study. Small number of nevi in the PUVA-treated group is another limitation. It is plausible that baseline dermoscopic feature of melanocytic nevus (reticular, globular, homogenous) affects the phototherapy-induced changes. Phototherapy parameters including number of treatment sessions and cumulative dose may also influence the result of our study. Due to small number of patients receiving 30 sessions of phototherapy (n = 5), a statistical analysis could not be performed. Further studies are required to elucidate how intrinstic features of each melanocytic nevus, different phototherapy protocols, and doses would possibly affect the response to UV.

In conclusion, our study shows that both PUVA and NB-UVB are likely to induce dermoscopic changes in 91.8% of irradiated melanocytic nevi. New dot/globule formation is the most common dermoscopic change in the nevi exposed to phototherapy followed by overall darkening, increase in the nevus size, and patchy pigmentation. We also observed that PUVA is associated with higher frequency of dermoscopic changes in both covered and uncovered nevi.

What is new?

This study provides a comparision of the dermoscopic changes of melanocytic nevi after exposure to therapeutic doses of NB-UVB or PUVA. Most nevi openly exposed to either NB-UVB or PUVA undergo dermoscopic alteration (91.8%). New dot/globule formation (62.1%) was the most common dermoscopic change followed by overall darkening (32.4%), increase in the nevus size (27%), and patchy pigmentation (18.8%). PUVA induces a higher rate of dermoscopic changes in irradiated nevi as compared to NB-UVB. Among nevi covered form direct irradiation, dermoscpoic changes were more frequently observed in the PUVA-treated patients. This may imply that paracrine factors of melanogenesis are more readily stimulated by PUVA.