[Analysis of 602 cases of nevus of Ota and study of ultrastructures on the melanocytes]

OBJECTIVE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Effect of Q-switched Alexandrite laser irradiation on epidermal melanocytes in treatment of Nevus of Ota

OBJECTIVE

To investigate injury to epidermal melanocyte by Q-switched Alexandrite laser.

METHODS

Multiple biopsies were performed on 5 patients with nevus of Ota from before irradiation to 1 year after irradiation. Fourteen specimens were obtained for light microscopy, and 17 for transmission electron microscopy.

RESULTS

Melanosomes in epidermal melanocytes were both smaller in size and fewer in number than those in dermal melanocytes. Immediately after irradiation, focal extracellular vacuoles of the basal layer could be observed under light microscopy. Most epidermal melanocytes underwent mild or moderate injury in the form of vacuolated melanosomes, swollen mitochondria, dilation of endoplasmic reticulum, and expansion of extracellular space, retaining intact cell membranes. Normal structures were restored 5 months to 1 year after irradiation, with no depigmentation or hyperpigmentation as seen by light microscopy.

CONCLUSION

Injury of melanosomes in epidermal melanocytes is reversible.

Effect of Q-switched alexandrite laser irradiation on dermal melanocytes of nevus of Ota

OBJECTIVE

To investigate the effect of Q-switched alexandrite laser irradiation on dermal melanocytes of nevus of Ota.

METHODS

Multiple biopsies were carried out on 4 patients with nevus of Ota before and after laser irradiation. Altogether 11 samples were examined under light microscope and 14 under transmission electron microscope.

RESULTS

Immediately after laser irradiation, the dermal melanocytes were destroyed, the melanosomes were degenerated with central vesicle formation within most of them, and intradermal round vacuoles appeared. The epidermis remained intact. Three months to 1 year after irradiation, the degenerated melanosomes and cell debris were scavenged mainly by macrophages. Dermal melanocytes gradually decreased. No fibrosis was found.

CONCLUSION

Q-switched alexandrite laser can selectively destroy dermal melanocytes of nevus of Ota and treat the disease safely.

Electron microscopic examination of oligocilia in naevus of Ota

The structure of the cilia present in dermal melanocytes of 14 patients with naevus of Ota was examined by electron microscopy. Cilia and basal bodies were found in 10 and 9 lesions, and in 39 and 18 dermal melanocytes, respectively. In each case, 1-12 cells with a single cilium or multiple cilia were observed. In a total of 3 dermal melanocytes from 2 cases, two cilia per cell were observed. The cilia contained 7, 6, 5 and 4 pairs of doublet microtubules in the periphery and no central microtubule. Another pattern with several pairs of doublet microtubules in the periphery and one or two centrally located doublet microtubules were also observed. The latter were not bona fide central microtubules but one and two doublets, which seemed to be displaced to the centre from the periphery of the cilium.

A role of SH-compounds in maturation of melanosomes in cells cultured from nevus Ota

A role of SH-compounds such as cysteine and glutathione in melanogenesis in dermal melanocytes cultured from Ota's nevus tissue was demonstrated in relation to another substrate, dihydroxyphenylalanine (DOPA). Chemical analysis of eumelanin and pheomelanin was performed in addition to the conventional electron microscopic observation. Supplements of the culture medium with each of these compounds separately for two weeks gave rise to the formation of pre-pheomelanosomes and secondary lysosomes or myelinosome-like inclusions. When DOPA and glutathione were added to the medium together, the maturation of melanosomes was promoted. This was proven by the increase in electron-density of pre-melanosomes observed as well as by the content of pheomelanin and eumelanin. However, mature melanosomes were not formed when each of these chemicals was added to the medium individually for the same periods. The melanosome maturation seemed to occur via a process involving secondary lysosomes or myelinosomes, in which more electron-dense particles accumulated in the presence of both reagents. The pheomelanosomal process was also observed, but typical eumelanosome-related processes were not observed in this culture system.

Treatment of nevus of Ota by Q-switched ruby laser

The effectiveness of the Q-switched ruby laser was investigated in 38 patients with nevus of Ota at more than 10 months after the first irradiation. In 14 patients who were followed-up for a mean of 25.2 months after the first treatment, the effectiveness was evaluated as "excellent" in eight patients (57%), "good" in four patients (28%), and "fair" in two patients (14%). The mean number of irradiation treatments was 7.3 in the "excellent" group, 4.2 in the "good" group, and 3.0 in the "fair" group. In 24 patients who were followed-up for a mean of 13.6 months after the first treatment, the effectiveness was evaluated as "excellent" in eight patients (33%), "good" in 12 patients (50%), and "fair" in four patients (16%). The mean number of irradiation treatment was 5.7 in the "excellent" group, 5.2 in the "good" group, and 2.5 in the "fair" group. Even after repetitive irradiations, good results without scarring were noted in all cases except one where a slight inverted scar was developed. The effective rate tended to be higher in patients who underwent more irradiation treatments and were observed for a longer period of time. Satisfactory cosmetic results were achieved after Q-switched ruby laser therapy for nevus of Ota.

Diffuse iris nevus in oculodermal melanocytosis: a light and electron microscopic study

We studied by light and electron microscopy the diffuse iris nevus of an eye in a 16-year-old patient with oculodermal melanocytosis and choroidal malignant melanoma. The nevus cells in the anterior border layer of the iris appeared to be poorly differentiated, showing moderate infolding of the nuclear membrane with heterochromatin clumping, watery cytoplasm, abundant mitochondria, fine filaments, rough endoplasmic reticulum, and numerous pinocytotic vesicles. Small scattered immature melanosomes and occasional giant melanosomes were observed in these cells. Deep in the iris stroma, however, nevus cells were found singly or in small groups, and were associated with an increasing number of melanized melanosomes and cytoplasmic filaments and reduced numbers of other cytoplasmic organelles, such as mitochondria and free ribosomes. Differentiation of the iris nevus cells appeared to progress from the anterior border layer toward the iris stroma. This observation suggests that intrastromal nevi may be more benign than nevi with surface plaque. The ultrastructural characteristics of the diffuse nevi of oculodermal melanocytosis were compared with those of other iris nevi.

Naevus fusco-caeruleus zygomaticus

One hundred and ten cases of an unusual type of naevus, which we have called naevus fusco-caeruleus zygomaticus were studied. The naevus presents as a bilateral speckled discolouration of the skin of the face principally in the zygomatic region. The condition usually does not become apparent until the second decade of life, and is much commoner in females. No association with any other abnormalities was found. Light and electron microscopy of the speckles showed the presence of dermal melanocytes mostly in the upper dermis. A survey was also carried out to determine the prevalence of this naevus in the general population.