To the Editor: A 57-year-old woman presented to our clinic for a pigmented patch on the left foot, which appeared 5 months earlier and progressively enlarged. She felt no pain or any other feelings. Physical examination revealed a light brown patch with an irregular shape and multiple colors, sized 10 mm × 8 mm on the left foot [Figure 1A].
Dermoscopic examination showed a parallel ridge pattern associated with irregular diffuse pigmentation. Multiple colors (light and dark brown, white, black, red), peripheral dots and globules, the regression structures, and surficial anabrosis were also observed [Figure 1B]. Eccrine pores are recognized as whitish dots regularly distributed within the band-like pigmentation.
The lesion was surgically removed and histopathologic analysis revealed the presence of confluent nests of atypical melanocytes with large hyper-chromatic nuclei scattered in the basal layer of the epidermis, and there was no dermal invasion [Figure 1C]. And the immunohistochemical examination showed that human melanoma black-45 (HMB-45) was positive in atypical melanocytes along the basal layer [Figure 1D], but S-100 was not expressed [Figure 1E]. All these findings were consistent with a diagnosis of acral lentiginous melanoma (ALM) in situ.
The challenge associated with early detection of melanoma faced by dermatologists as well as patients is the key strategy for reducing the mortality and economic burden associated with it. The application of dermoscopy has significantly enhanced diagnostic accuracy over naked-eye examination with various diagnostic patterns and algorithms. But the majority of these criteria were established with later-stage invasive melanomas, making identification and diagnosis of melanoma in situ challenging.
ALM is the most common type of cutaneous melanoma in Asians. Dermoscopy appears to be a valuable tool for the early diagnosis of ALM. The most common and specific dermoscopic finding in early (including in situ) ALM is the presence of parallel ridge pattern, which has a specificity of 99%, and a positive predictive value of 84%. The second most common pattern in ALM is the irregular diffuse pigmentation pattern consists of pigmented blotches of various shades of brown, which has a specificity of 96.6%. There are also some other dermoscopic features in ALM, such as the serrated pattern which consists of projections (similar to streaks) at the edge of the tumor and multi-component pattern including abrupt edge, irregular pigmentation, atypical dots and globules, multiple colors, atypical streaks, and so on.
In this case, there are not only parallel ridge pattern, irregular diffuse pigmentation, atypical dots and globules, and regression structures, but the milk-red area and surficial anabrosis which are often found in invasive melanomas. Further studies are needed to complete the dermoscopic features of ALM in situ, especially in Asian.
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The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given her consent for her images and other clinical information to be reported in the article. The patient understands that her name and initials will not be published and due efforts will be made to conceal the identity of the patient, although anonymity cannot be guaranteed.
Conflicts of interest
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