A Rare Case of Aggressive Melanotic Schwannoma Occurred in Spinal Nerve of a 59-Year-Old Male

Melanotic schwannoma (MS) is a rare variant of nerve sheath neoplasm that shows ultrastructural and immunophenotypical features of Schwann cells but also has cytoplasmic melanosomes and is reactive for melanocytic markers as well. Unlike conventional schwannoma, which is totally benign, MS has an unpredictable prognosis and is thought to have low-malignant potential. Herein, we present a rare case of recurrent MS in lumbar spine of a 59-year-old male.

Pigmentation Effect of Electromagnetic Fields at Various Intensities to Melanocytes

Melanogenesis is the biological process that results in the synthesis of skin pigment of melanin and it has various functions in living systems and is synthesized by the melanosome within the melanocytes. A variety of physical treatments are used to promote melanin production in the melanocytes for pigmentation control. The purpose of this study was to evaluate the intensity-dependent effect of extremely low-frequency electromagnetic fields (ELF-EMFs) on melanogenesis by melanocytes in vitro. Melanocytes were exposed to ELF-EMFs at a frequency of 50 Hz and at intensities in the range of 0.5–20 G over 4 days. The results of lactate dehydrogenase assay showed that there were no significant differences between cells exposed to 0.5 G or 2 G groups and the controls. The melanin contents increased 1.2–1.5-fold in cells exposed to ELF-EMFs and tyrosinase activity increased 1.3-fold in cells exposed to ELF-EMFs, relative to the controls. Also, exposure to ELF-EMFs was associated with activation in cyclic-AMP response element binding protein and microphthalmia-associated transcription factor (MITF) was up-regulated. Up-regulation of MITF induces the expression of melanogenesis-related markers, such as tyrosinase, tyrosinase-related protein (TRP)-1, TRP-2. In conclusion, the present study showed that the exposure to ELF-EMFs at low intensities can stimulate melanogenesis in melanocyte, and these results may be used to a therapeutic devices for inducing repigmentation in vitiligo patients.

Effect of MITF-M and MITF-A Overexpression on the Dendrtic Formation in Melanocytes / 체질인류학회지

The microphthalmia-associated transcription factor (MITF), has been described as the master regulator of the basic helix-loop-helix leucine zipper family, involves melanogenesis in melanocytes. MITF consists of at least six isoforms, called MITF-M, MITF-A, MITF-B, MITF-C, MITF-H, and MITF-J. Previously, we found that not only MITF-M is expressed in the human hair follicle, but also MITF-A, MITF-C, MITF-H, and MITF-J isoforms are expressed in the skin. The aim of this study was to conform the MITF isoforms expressed in human skin, and investigate novel role of MITF isoforms in the melanocytes. Expression of MITF-M and MITF-A was found in primary melanoctyes and the melanoma cell lines. Interestingly, when MITF-M and MITF-A were overexpressed in the SK-MEL-24 melanoma cells by adenoviral transfection, length of the dendrites, serves as the principal conduit for melanosomes transfer, was significantly increased in the MITF-M overexpressed cells compared with the control group, and number of the dendtrites was significantly increased in the MITF-A overexpressed cells. A signal molecule involve in actin polymerization during dendrite formation, Rac1, was increased in the SK-MEL-24 melanoma cells treated with adenoviral MITF-M and MITF-A vectors. These results suggest that MITF-M and MITF-A induce dendrite formation via Rac1 signaling in the melanocytes.

Influence of Pulse Type on Subcellular Selective Photothermolysis of Melanosomes in Adult Zebrafish Skin Following 1,064-nm, Q-switched, Nd:YAG Laser Irradiation: A Pilot Study

No abstract available.

Protease-Activated Receptor-2 Is Associated with Terminal Differentiation of Epidermis and Eccrine Sweat Glands

BACKGROUND: Protease-activated receptor 2 (PAR-2) participates in various biological activities, including the regulation of epidermal barrier homeostasis, inflammation, pain perception, and melanosome transfer in the skin. OBJECTIVE: To evaluate the basic physiological role of PAR-2 in skin. METHODS: We investigated PAR-2 expression in human epidermis, skin tumors, and cultured epidermal cells using western blot and immunohistochemical analysis. Additionally, we examined the effect of the PAR-2 agonist, SLIGRL-NH2, on cultured keratinocytes. RESULTS: Strong PAR-2 immunoreactivity was observed in the granular layer of normal human skin and the acrosyringium of the eccrine sweat glands. In contrast, weak PAR-2 immunoreactivity was seen in the granular layer of callused skin and in the duct and gland cells of the eccrine sweat glands. Interestingly, PAR-2 immunoreactivity was very weak or absent in the tumor cells of squamous cell carcinoma (SCC) and syringoma. PAR-2 was detected in primary keratinocytes and SV-40T-transformed human epidermal keratinocytes (SV-HEKs), an immortalized keratinocyte cell line, but not in SCC12 cells. SV-HEKs that were fully differentiated following calcium treatment displayed higher PAR-2 expression than undifferentiated SV-HEKs. Treatment of cultured SV-HEKs with PAR-2 agonist increased loricrin and filaggrin expression, a terminal differentiation marker. CONCLUSION: Our data suggest that PAR-2 is associated with terminal differentiation of epidermis and eccrine sweat glands.

Clinicopathologic Features of Progressive Macular Hypomelanosis in Korea / 대한피부과학회지

BACKGROUND: Progressive macular hypomelanosis, a disease of uncertain etiology, was first described by Guillet et al. in 1988. It is characterized by asymptomatic hypopigmented macules and patches that appear on the trunk and upper extremities. It is a relatively recently described disorder and more case reports are needed. OBJECTIVE: The purpose of the study was to document the clinicopathologic and ultrastructural features of progressive macular hypomelanosis in Korean patients. METHODS: Patients who presented to our hospital and were diagnosed with progressive macular hypomelanosis from July 2009 to June 2014 were enrolled in this study. Skin scrapings were taken for fungal tests, and skin biopsy specimens from lesional and normal skin were obtained. Sections of the skin biopsies were stained with hematoxylin and eosin, Brown and Brenn Gram stain, and Fontana-Masson stain, and they were incubated with a panel of immunohistochemical reagents used to identify melanocytes, namely, gp-100, melan-A, and microphthalmia-associated transcription factor. The tissues from two patients were also examined using electron microscopy. RESULTS: Over the course of 5 years, 16 patients presented with ill-defined hypopigmented macules on their trunks and upper extremities. The mean age of the patients was 28.4+/-9.0 years and the male to female ratio was about 1 : 4. Histopathologically, lesional skin showed a reduced level of pigmentation, while the number of melanocytes was preserved. None of the patients showed bacterial colonization of the pilosebaceous units. Electron microscopy demonstrated smaller and less melanized melanosomes in the lesional keratinocytes. CONCLUSION: Progressive macular hypomelanosis is a hypopigmentary disorder that is characterized by a loss of melanosomes without damage to the melanocytes. Although there are several reports that describe a possible relationship between Propionibacterium acnes and progressive macular hypomelanosis, it remains unclear.

Possible Existence of Melanocytes or Melanoblasts in Human Sebaceous Glands

BACKGROUND: Melanocytes are present in both basal epidermis and hair follicles. Melanocyte stem cells have been found in hair follicle bulge. During embryogenesis, the outer cells of the bulge differentiate into the sebaceous gland (SG) and proliferate. OBJECTIVE: To identify and determine the distribution and morphological characteristics of melanocytes in human SGs. METHODS: A total of 171 biopsy specimens of face and scalp were studied. Of these specimens, 103 samples contained SGs. We conducted a retrospective review of slides stained with H&E, F-M, anti-S100, anti-c-kit, anti-HMB-45, anti-CD1a, anti-MITF, and anti-tyrosinase. The presence and distribution of melanocytes in human SGs was also evaluated by electron microscopy. In addition, melanocytes were isolated from SGs for primary culture. RESULTS: S-100-positive cells were observed mainly at the periphery of SGs in 34 of 54 specimens. We did not find F-M-positive and HMB-45-positive cells in SGs. CD1a-positve cells were identified in two specimens. We also found c-kit-, MITF-, and tyrosinase-positive cells in SGs. Electron micrograph showed the presence of melanocytes in the suprabasal portion of SGs. These melanocytes showed fewer melanin-containing granules than the melanocytes of basal epidermis. However, the individually distributed melanosomes in suprabasal melanocytes were larger than those in epidermal melanocytes. Primary culture of melanocytes derived from SGs showed morphologically homogeneous, slender cell bodies with few dendrites. CONCLUSION: Our study confirms the presence of non-melanogenic melanocytes and Langerhans cells in human SGs. In addition, the characteristics of the melanocytes in SGs were found to be different from those of the epidermal melanocytes.

Hesperidin Suppresses Melanosome Transport by Blocking the Interaction of Rab27A-Melanophilin

We investigated the inhibitory effects of hesperidin on melanogenesis. To find melanosome transport inhibitor from natural products, we collected the structural information of natural products from Korea Food and Drug Administration (KFDA) and performed pharmacophore-based in silico screening for Rab27A and melanophilin (MLPH). Hesperidin did not inhibit melanin production in B16F10 murine melanoma cells stimulated with alpha-melanocyte stimulating hormone (alpha-MSH), and also did not affect the catalytic activity of tyrosinase. But, hesperidin inhibited melanosome transport in melanocyte and showed skin lightening effect in pigmented reconstructed epidermis model. Therefore, we suggest that hesperidin is a useful inhibitor of melanosome transport and it might be applied to whitening agent.

A Simple Assay Method for Melanosome Transfer

Pigmentation is induced by production of melanin in specialized organelles termed melanosomes and by transfer of these organelles from melanocytes to surrounding keratinocytes. The chemical basis of melanogenesis is relatively well known but the mechanism of melanosome transfer is not well studied. Various pigmentary disorders and cosmetic applications require the use of depigmenting agents. Currently available topical agents used for the reduction of pigmentation mainly include tyrosinase inhibitors and/or melanocyte-cytotoxic agents. Recently, several agents have been introduced to inhibit melanosome transfer from melanocytes to keratinocytes. However, an experimental model for melanosome transfer is not well established. In this study, a simple assay method using flow cytometry is described.

Topical Hypopigmenting Agents for Pigmentary Disorders and Their Mechanisms of Action

Melanin is produced in melanocytes and stored in melanosomes. In spite of its beneficial sun-protective effect, abnormal accumulation of melanin results in esthetic problems. Hydroquinone, competing with tyrosine, is a major ingredient in topical pharmacological agents. However, frequent adverse reactions are amongst its major limitation. To solve this problem, several alternatives such as arbutin, kojic acid, aloesin, and 4-n-butyl resorcinol have been developed. Herein, we classify hypopigmenting agents according to their mechanism of action; a) regulation of enzyme, which is subdivided into three categories, i) regulation of transcription and maturation of tyrosinase, ii) inhibition of tyrosinase activity, and iii) post-transcriptional control of tyrosinase; b) inhibition of melanosome transfer, and c) additional mechanisms such as regulation of the melanocyte environment and antioxidant agents.

The Correlation of the Expression of Foxn1 and the Pigmentation in Various Pigmentary Disorders / 대한피부과학회지

BACKGROUND: Transfer of melanosomes from melanocytes to the neighboring keratinocytes is a critical step in normal pigmentation. However, the mechanism of melanosome transfer and the regulation of pigmentation by the keratinocyte-melanocyte interactions are not well understood. It has recently been identified that keratinocytes use Foxn1 (transcription factor) to recruit melanocytes and induce their own pigmentation. OBJECTIVE: The purpose of this study was to assess the expression of Foxn1 in hypopigmentary disorders (vitiligo, pityriasis alba (P. alba) and postinflammatory hypopigmentation (PIHo)) and hyperpigmentary disorders (melasma, caf?-au-lait macule (CALM) and postinflammatory hyperpigmentation (PIHer)). METHODS: Immunohistochemical staining was performed on the formalin-fixed, paraffin-embedded tissue sections of hypopigmentary and hyperpigmentary disorders using anti-Foxn1 antibody with an avidin-biotin peroxidase complex procedure. The intraepidermal melanin pigments were examined in all the lesions by Fontana-Masson staining. RESULTS: We found a significantly lower Foxn1 expression (p<0.05) and less intraepidermal melanin pigments (p< 0.01) in the hypopigmentary disorders as compared to that of the hyperpigmentary disorders. In the hypopigmentary disorders such as vitiligo, P. alba and PIHo, the expression of Foxn1 was decreased in the order named. In thehyperpigmentary disorders such as CALM, PIHer and melasma, the expression of Foxn1 was increased in the order named. CONCLUSION: The intraepidermal Foxn1 expression and melanin pigments in PIHer, PIHo and melasma showed a positive correlation, but there was no statistically significant. Our findings suggest that the expression of Foxn1 might be associated with the pathogenesis of three pigment disorders (PIHo, PIHer, melasma). We consider that inflammatory mediators might interact with the intraepidermal Foxn1 expression in PIHo, PIHer and melasma, resulting in an abnormality of the mechanism of melanosome transfer. Further studies are warranted to elucidate the role of the Foxn1 expression in the pathogenesis of pigment disorders.

Ultrastructure in resolving a diagnosis of poorly differentiated clear cell sarcoma of soft parts in an adolescent male.

Clear cell sarcoma of soft parts is a rare tumor in children and it requires a high index of suspicion for accurate diagnosis. Early diagnosis leads to radical surgical excision and limits the aggressive behavior of this tumor. We report a case of a 12-year-old boy with a recurrent soft-tissue tumor in the scalp, misdiagnosed on three occasions as epitheloid sarcoma owing to the poorly differentiated appearance of cells. In spite of focal S-100 expression, this tumor was not recognized as a tumor of melanocytic origin till melanosomes were demonstrated on electron microscopy (EM). Detection of melanosomes on electron microscopy helped in clinching the histology diagnosis, reiterating the definite role of EM in diagnosing these tumors. Failure to accurately diagnose this tumor resulted in institution of preoperative chemotherapy, delayed surgical excision, tumor progression and death of patient within a year and half of presentation.

First report of Griscelli syndrome from Afghan population in Iran

A 4 month old Afghan male infant presented with partial albinism, hepatosplenomegaly and pancytopenia. Skin and hair shaft microscopic examination revealed large clumped melanosomes and Griscelli syndrome was diagnosed. Unless treated with bone marrow transplantation, it is a fatal disease in accelerated phase. Pediatricians should consider this syndrome in infants with abnormal light hair because early diagnosis could be life saving

Alpha1 and alpha2 adrenoceptor mediated melanosome aggregatory responses in vitro in Oreochromis mossambica (Peters) melanophores.

Effects of specific and non-specific adrenoceptor agonists and antagonists were examined on the isolated scale melanophores of O. mossambica in physiological Ringer solution. The responses were recorded as melanophore size index. It was observed that adrenaline, nor-adrenaline, phenylpropanolamine, clonidine and phenylepherine induced melanosome aggregation in a dose-dependent manner. Denervation of the fish melanophores increased the sensitivity of the melanophores to adrenaline but not to nor-adrenaline. Phentolamine (3.55 x 10(-5) M), prazosin (2.38 x 10(-5) M) and yohimbine (2.821 x 10(-5) M) significantly inhibited the aggregatory responses of the fish melanophores to adrenaline, nor-adrenaline, clonidine and phenylepherine. The blocking effect of yohimbine was significantly higher than that of prazosin. It is concluded that the effect of adrenaline is directly mediated through the receptors and alpha2 adrenoceptors are predominantly involved in the aggregatory responses of this fish melanophores, while alpha1 adrenoceptors presence has been indicated.

Evaluation of the efficacy of the Q switched ruby laser in the treatment of benign pigmented skin lesions

It is possible to use light sources such as lasers to destruct melanosomes and treat pigmented skin lesions. One of the most commonly used laser systems is Q switched ruby laser with a wave-length of 694 nm. This study was performed to evaluate the efficacy of the Q switched ruby laser in the treatment of pigmented skin lesions including lentigines [simplex or solar] and cafe-au-lait macules. After physical examination for ruling out the possibility of malignancy by two dermatologists, patients were treated with Q switched ruby laser. Response to treatment was categorized in four groups of equal interval according to the 0-100% lesion lightening. Ninety patients including 81 patients with solar lentigo and 9 cases of lentigo simplex were recruited into this study. Mean st and ard deviation [SD] of the number of treatment sessions for solar lentigo and lentigo simplex cases were 1.0 0.5 and 3.6 1.3 respectively. Although the mean of sessions was increased in darker skin types, there was no statistically significant difference between different skin types [p=0.335]. In addition, there was no significant relation between mean treatment sessions and location of the lesions [p=0.685]. Cure rate was 100% in all lentigo cases and after a mean SD of 8.7 2.3 months follow up there was no recurrence. Also, there was neither pigmentary change nor folliculitis during treatment. In 7 cases with cafe-au-lait macules, the mean SD score of improvement was 2.4 0.8, which was achieved after 3.1 0.4 treatment sessions. In 6 cases whom were followed up for 10.2 3.1 months, despite primary disappearance, recurrence of cafe-au-lait macules was observed. It seems Q switched ruby laser is an appropriate method for treatment of lentiginous lesions in Caucasians with Fitzpatrick's skin types II to IV

Application of Tyramide Signal Amplification (TSA) Both to Biochip Platform and to the Immunoelectron Microscopy to Label Proteins within the Organelle / 대한해부학회지

The tyramide signal amplification (TSA) technique, based on the ability of HRP to catalyze the deposition of tyramide onto the surrounding proteins, has been proved to detect scarce tissue antigens. In this study we applied this technique to a biochip platform and an immunocytochemistry at the electron microscopic level. First, in the optical fluorescence sensing, the signal was amplified by Dako Envision(TM) (goat anti-mouse immunoglobulins IgG conjugated to peroxidase labelled-dextran polymer) and tyramide-Cy3, which was then compared to the non-amplified control using goat antimouse IgG-Cy3 conjugate instead. The result showed that the tyramide method produced a more sensitive signal than the control method. Secondly, in the pre-embedding immunocytochemistry, we investigated to see whether it is possible to label proteins within a organelle in the cell using the TSA method. The signal was amplified by a primary antibody, a biotinylated secondary antibody, streptavidin-HRP, biotinyl-tyramide, and streptavidinnanogold followed by silver enhancement and gold toning. Then, this protocol was compared to the non-amplified or simple protocol that does not include the steps of streptavidin-HRP and biotinyl-tyramide. With the TSA protocol, the labeling for a membrane bound antigen (gp100) that is known to be exclusively localized to melanosomes in melanocyte, was tested in a melanoma cell line (G361) and found to be highly sensitive and more enhanced than with the simple protocol. Moreover, the gold particles were well localized to the subcellular structures or melanosomes both in the TSA and simple protocols, which indicates that resolution of the signals remains high. Control experiment with omission of the primary antibody demonstrated that background levels or nonspecific bindings are negligible. This result showed that the TSA method can be successfully applied to label the intra-organelle protein that is known to be labeled only in the specific fixation condition with the optimal permeability.

The Effects of Keratinocyte-derived Factors Involved in Transforming the Morphologies of Melanocyte and in Translocating Melanosomes to Keratinocyte / 대한해부학회지

Keratinocyte-derived factors are involved in regulating the proliferation, differentiation or melanogenesis of melanocytes. To investigate the effects of keratinocyte-derived factors on the skin pigmentation, human melanocytes and keratinocytes were cultivated in the forms of pure melanocyte or keratinocyte culture system, co-culture system (melanocytes and keratinocytes were cultivated together in a vessel but they were separated with semipermeable membrane) or mixed culture system (melanocytes and keratinocytes were cultivated together in a vessel in mixed form). The authors studied the cellular features (dendritogenesis and area) and the tyrosinase activities and observed the electron microscopic structures for melanosome transfer. Melanocyte in co-culture system increased in the area (p.0.05) but not in the dendritogenesis compared with the melanocyte in pure culture system. The tyrosinase activities of co-culture system on the 2nd and 4th day revealed higher compared with the ones of the pure and mixed culture system (p.0.05). In the co-culture system, the tyrosinase activities were gradually decreased with the lapse of time and vice versa in the pure and mixed culture system. On the 6th day culture, all of the three melanocyte culture systems showed the same tyrosinase activities. In spite of high tyrosinase activities in the medium, there were no tyrosinase activities in keratinocytes with the co-culture system. In transmission electron microscopic findings, there were scant of melanosomes in keratinocytes with the co-culture and mixed culture systems. In conclusion, keratinocyte-derived factors modulate the activities and melanogenesis of melanocytes but there were no effects on melanosome transfer to keratinocytes.

Strong Association of HMB - 45 expression with renal angiomyolipoma

Angiomyolipoma [AML] is a benign neoplasm consisting of varying mixtures of smooth muscle, blood vessels and fat. Although, most of these tumors are easy to recognize, some may pose a diagnostic dilemma due to unusual histologic features. Recently, it was suggested that melanosome-associated protein [HMB-45] immunoreactivity may be used for diagnostic confirmation of several neoplasm. The aim of this study is to analyze the diagnostic efficacy of HMB-45 in patients with AML. This study was carried out at the Faculty of Medicine, Department of Pathology, Dicle University, Diyarbakir, Turkey, during the period January 2000 to September 2003. HMB-45 immunoreactivity was analyzed in 6 patients with AML and in 34 patients with other renal and retroperitoneal pathologies, including 10 nephrectomized patients for non-neoplastic reasons by means of immunohistochemistry. Patients with AML were positive for HMB-45. Whereas, HMB-45 immunoreactivity was negative in all of the histologic specimens from the patients with renal cell carcinoma, retroperitoneal sarcomas, Wilms' tumor, lipoma, leiomyoma, and nephrectomized kidneys of non-neoplastic reason. The association of AML with HMB-45 immunoreactivity was highly significant [p<0.001]. Our findings suggest that HMB-45 may not be a melanocyte-restricted marker, and can be useful in differential diagnosis between AML and other tumors seen in kidney and retroperitoneal region

Histopathologic, Immunohistochemical, and Electron Microscopic Findings of Pigmented Skin Lesions Immediately after Q-switched Alexandrite Laser Treatment / 대한피부과학회지

BACKGROUND: There have been only a few electron microscopic studies after laser treatment of pigmented skin lesions. OBJECTIVE: The purpose was to investigate the pathologic, immunohistochemical, and electron microscopic changes following Q-switched alexandrite laser treatment of pigmented skin lesions. METHODS: Three patients with acquired bilateral nevus of Ota-like macules, and 2 patients with cafeau lait macule were irradiated with Q-switched alexandrite laser. Forty biopsies were taken before and immediately after laser treatment. Hematoxylin-eosin, Fontana-Masson, and gp100 staining were performed for the evaluation of the histopathologic and immunohistochemical findings of the specimens. Electron microscopic findings were also evaluated. RESULTS: Histopathologically, suprabasilar separations were observed immediately after laser treatment. Vacuolar alterations of pigment-containing cells were frequently found in the epidermis and/or in the dermis. Fontana-Masson and gp100 staining positivity changed to negative or decreased in the epidermis immediately after laser treatment, while they changed to negative in the dermis. Ultrastructurally, epidermal pigment-containing cells frequently showed severe vacuolar changes in the cytoplasm, pyknotic nuclei, and vacuolated and/or fragmented melanosomes immediately after laser treatment. Dermal melanocytes frequently revealed vacuolated and/or fragmented melanosomes immediately after laser treatment. CONCLUSION: Histopathologic, immunohistochemical, and electron microscopic examination of pigmented skin lesions immediately after Q-switched alexandrite laser treatment demonstrated vacuolated or fragmented melanosomes and vacuolar alteration of pigment-containing cells in the epidermis and/or in the dermis, which suggested selective photothermolysis of melanosomes.

Analysis of 602 cases of nevus of Ota and study of ultrastructures on the melanocytes / 中国医学科学院学报

<p><b>OBJECTIVE</b>To analyze clinical information and efficacy of 602 cases of nevus of Ota, and investigate the histopathology and ultrastructure on the melanocytes before and after Q-switched Alexandrite laser irradiation.</p><p><b>METHODS</b>Clinical information of 602 cases of nevus of Ota were collected by applying clinical records, checking photos, and inquiry to patients by letters and telephones. Ten cases of biopsies were observed by light microscopy and 6 cases by electron microscopy before and after laser irradiation.</p><p><b>RESULTS</b>Nevus of Ota included congenital and acquired cases. Skin lesions mainly occurred in adolescence for the acquired cases. The main colours of lesions were brown and blue. The most local lesions were zygomata, temporal regions, and lower eyelids. According to multiple regression, the more treatment times, the better results. The effective rate was 85.20% and 100% after 6 and 9 treatment times, respectively, while the cure rate was 55.72% and 98.46%, respectively. The eyelids involved and Tanino types influenced the treatment times by COX models analysis. Electron microscopy showed many melanosomes in the dermal melanocytes. After laser irradiation, the outlines of the dermal melanocytes were observed, the melanosomes were broken to dense and tiny granules.</p><p><b>CONCLUSIONS</b>Q-switched Alexandrite laser is safe and effective for the treatment of nevus of Ota. The results of treatment are correlated with the area and size of the lesion. The dermal melanocytes in nevus of Ota can be selectively destroyed by Q-switched Alexandrite laser with less injury around tissues.</p>