SummaryBackground Melasma is a common acquired symmetrical hypermelanosis characterized by irregular light to dark brown macules and patches on sun-exposed areas of the skin. Its histopathological characteristics are not fully understood. Objectives To characterize the histopathological features of facial melasma skin in comparison with adjacent normal skin. Methods Biopsies were taken from both melasma lesional skin and adjacent perilesional normal skin in 56 Korean women with melasma. The sections were stained using haematoxylin and eosin, Fontana±Masson, diastase-resistant periodic acid-Schiff, Masson trichrome and Verhoeff±van Gieson stains, and immunostaining for melanocytes. Data on the changes in number of melanocytes and melanin contents of the epidermis were analysed by a computer-assisted image analysis program. The ultrastructure of the skin was also examined. Results The amount of melanin was signi®cantly increased in all epidermal layers in melasma skin. The staining intensity and number of epidermal melanocytes increased in melasma lesions. Lesional skin showed more prominent solar elastosis compared with normal skin. Melanosomes increased in number and were more widely dispersed in the keratinocytes of the lesional skin. Lesional melanocytes had many more mitochondria, Golgi apparatus, rough endoplasmic reticulum and ribosomes in their cytoplasm. A dihydroxyphenylalanine reaction was apparent in the cisternae and vesicles of the trans-Golgi network in melanocytes from lesional skin. Conclusions Melasma is characterized by epidermal hyperpigmentation, possibly caused both by an increased number of melanocytes and by an increased activity of melanogenic enzymes overlying dermal changes caused by solar radiation.

Extranodal NK/T-cell lymphomas are extremely aggressive regardless of their subgroup. However, the 'nasal-type' NK/T-cell lymphoma was clinically less aggressive, more localized and had a better outcome compared with the other type. Cellulitis and ulcer were the major cutaneous manifestations.

Objectives: The objective of this study was to determine the in vivo efficacy of radiofrequency ablation (RFA) in porcine liver using Octopus j electrodes for creating a large coagulation compared with RFA using clustered electrodes. Methods: A total of 39 coagulations were created using a 200-W generator and clustered electrodes or Octopus electrodes during laparotomy in 19 pigs. Radiofrequency was applied to the livers using four protocols: (1) Group A-1, monopolar mode using a clustered electrode (n511); (2) Group A-2, monopolar mode using an Octopus electrode (n511); (3) Group B-1, consecutive monopolar mode using three, clustered electrodes (n58); and (4) Group B-2, switching monopolar mode using two Octopus electrodes (n59). The energy efficiency, shape, diameters (D) and volume (V) of the coagulation volume were compared in each of the two groups. Results: The mean maximum D and V of the coagulations in Group A-2 (4.7 cm and 33.1 cm 3 , respectively) were significantly larger than those in Group A-1 (4.1 cm and 20.3 cm 3 , respectively) (p,0.05). Furthermore, the mean minimum D, maximum D and V of the coagulations in Group B-2 were significantly larger than those in Group B-1, i.e. 5.3 vs 4.0 cm, 6.6 vs 4.9 cm and 66.9 vs 30.2 cm 3 , respectively (p,0.05). The energy efficiencies were also significantly higher in Groups A-2 and B-2 than in Groups A-1 and B-1 (p,0.05). Conclusion: The Octopus electrodes were more efficient for creating a large ablation zone than clustered electrodes, and the efficacy of RFA with Octopus electrodes can be amplified in the switching monopolar mode.

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planus. 2,3 The several varieties of apoptotic markers studied in the literature and the rarity of this lesion may explain in part the result's variation.Exploration of the cell proliferate degree exposed different results depending on the antibody used. In fact, in the epithelial basal layer, the proliferation rate varied between 36% with the anti-Ki67 antibody (inset image in Fig. 2a) and 70% with the antiproliferating cell nuclear antigen (anti-PCNA) antibody (Fig. 2b). Even suprabasal keratinocytes were positive to the anti-PCNA antibody. In the lymphocytic infiltrate, although Ki-67 was not detected (Fig. 2a), 30% of the lymphocytes expressed the PCNA (Fig. 2b). Because of its relatively long half-life, PCNA protein may be detected in cells that have left the cell cycle. 4 This may explain why we detected this protein in a more extensive way than the other proliferate marker, Ki-67. On the other hand, a statistical analysis have shown that when compared with normal mucosa, the expression of the PCNA is really significantly higher in the layers of the oral lichen planus 5 assessing our findings of a high proliferation ratio in the basal keratinocytes.Moreover, characterization of the infiltrating lymphocytes assessed that they are T cells (CD3 + ) and that 36% of them are of killer type (CD8 + ). Neither helper T lymphocytes (CD4 -) nor B lymphocytes (L26 -) were detected in the subepithelial infiltrate. Several studies have assessed that infiltrating cells in oral lichen planus are CD-4-positive and CD-8-positive T cells with a variable proportions. 6,7 Although we confirmed the T nature of the lymphocytes, we failed to detect the T helper cells (CD4 -) in the subepithelial infiltrate, that is in disagreement with previous studies on oral lichen planus. 8 These data may be explained by the fact that (i) these previous studies did not explore the very rare pigmentosus variety of lichen planus, or (ii) the biopsy studied here is of late stages of disease since a gradual accumulation of CD8 + cells is reported with disease progression. 9 Especially for the epithelial basal cell layer, the apoptosis process seems to affect more cells than do the proliferation one. These data are approved by a study that revealed an association between the Ki67 expression and the wild p53 expression in oral lichen planus 10 confirming the antitumoral role of p53 and explaining the low rate of malignant transformation observed in this disease.The results emphasize the originality of this case in two points: the relative low rate of apoptotic basal keratinocytes and the killer nature of the T cells infiltrating the lesion. Further reports are required confirming these findings to be particular to this rare lesion. EditorEpidermal cysts are the most common cutaneous cysts and can develop at any location of the body. While epidermal cysts Figure 2 Cells of the subepithelial infiltration express the proliferative marker Ki67 (a). Inset, few basal keratinocytes also show nuclear expression of Ki67. Several keratinocytes and infiltrati...