Acral viral wart showing a parallel ridge pattern on dermatoscopy

ARTICLE

Auteur(s) : Nicola Arpaia¹, Raffaele Filotico², Valentina Mastrandrea¹, Nicoletta Cassano¹, Gino A Vena¹

¹2nd Dermatology Clinic, Department of Internal Medicine, Immunology and Infectious Diseases, University of Bari, Bari, I-70124, Italy
²Unit of Dermatology, Ospedale ‘A. Perrino’, I-72100 Brindisi, Italy

Dermatoscopy has notably improved the diagnostic accuracy of melanocytic lesions, including those on acral skin. Acral melanocytic lesions show characteristic dermatoscopic patterns, which differ from those of lesions located on other sites [1]. Parallel ridge pattern was found to have an important diagnostic value in early acral melanoma [1-3]. We describe here the case of an acral viral wart resembling a malignant melanoma on dermatoscopy because of the presence of a parallel ridge pattern.

A 23-year-old woman presented with an asymptomatic pigmentary macule on the volar surface of the first finger of her left hand. The patient reported that this macule had appeared three years before and gradually increased in size over time, showing a relatively fast growth during the last year. The lesion was flat and roughly ovoidal, with a maximum diameter measuring nearly 9 mm. A light brown colour was evident in most parts with a darker mottled pigmentation irregularly distributed inside the lesion. On dermatoscopic examination, there was a band-like pigmentation on the ridges of the skin markings consistent with a parallel ridge pattern (figure 1A). Therefore the lesion was surgically excised. Histopathological study of a haematoxylin and eosin stained specimen showed gross hyperkeratosis and acanthosis in the epidermis; large vacuolated cells with the typical features of koilocytes were present in the malpighian and granular layers (figure 1B). The absence of abnormal melanocyte proliferation revealed on histopathology was confirmed by S-100 staining; epidermal cells showing cytopathic signs were S-100 negative. Based on these features, the histopathological diagnosis was viral wart.

It is well known that acral malignant melanoma may mimic several cutaneous lesions, including warts, especially when melanoma is poorly pigmented. If malignant melanoma is misdiagnosed as a wart, the subsequent inadequate treatment with curettage or cryotherapy may present a severe risk of tumoral progression and can negatively impact on the final prognosis. Dermoscopy has led to a significant improvement in the diagnostic accuracy of skin tumors and is also useful in differentiating malignant melanomas from melanocytic nevi on palms and soles [1]. The majority of melanocytic nevi on acral skin show three main dermoscopic patterns: the parallel-furrow pattern, the lattice-like pattern, and the fibrillar pattern. The parallel ridge pattern is considered highly specific to acral malignant melanoma and helpful in detecting acral melanomas in early stages. Such a dermoscopic pattern was found to show extremely high specificity (nearly 99%) and very high negative predictive value (up to 97.7%) in acral volar malignant melanoma [2]. Histopathological study of melanoma on volar skin revealed that this pattern corresponded to a prominent proliferation of atypical melanocytes in the crista profunda intermedia [3]. However, the parallel ridge pattern has been sporadically described in skin lesions other than melanomas at acral sites, including subcorneal hematomas, combined blue nevi, and atypical melanosis [4-6]. The parallel ridge pattern can also be found in acral viral warts, as suggested by the case herein described, which is, to the best of our knowledge, the first literature report of a wart dermoscopically simulating acral melanoma. In the case of dermatoscopically and/or clinically suspicious lesions, surgical excision is strongly recommended, since only histological examination allows the correct diagnosis.

Acknowledgements

References

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