Amelanotic/hypomelanotic melanoma: clinical and dermoscopic features.
Background: Amelanotic malignant melanoma is a subtype of cutaneous melanoma with little or no pigment on visual inspection. It may mimic benign and malignant variants of both melanocytic and nonmelanocytic lesions.
Objective: To evaluate whether dermoscopy is also a useful technique for the diagnosis of amelanotic/hypomelanotic melanoma (AHM).
Methods: We conducted a retrospective clinical study of 151 amelanotic/hypomelanotic skin lesions from 151 patients with a mean age of 47 years (+/- 17.5 SD). Digitized images of amelanotic/hypomelanotic skin lesions were converted to JPEG format and sent by e-mail from the five participating centres. Lesions included 55 amelanotic/hypomelanotic nonmelanocytic lesions (AHNML), 52 amelanotic/hypomelanotic benign melanocytic lesions (AHBML), and 44 AHM, 10 (23%) of which were nonpigmented, truly amelanotic melanomas (AM). The 44 AHM lesions were divided into thin melanomas (TnM) 1 mm (15 cases), according to the Breslow index. Five clinical features (elevation, ulceration, shape, borders and colour) as well as 10 dermoscopic criteria (pigment network, pigmentation, streaks, dots/globules, blue-whitish veil, regression structures, hypopigmentation, leaf-like areas, multiple grey-bluish globules, central white patch) and eight vascular patterns (comma, arborizing, hairpin, dotted, linear irregular, dotted and linear irregular vessels, and milky-red areas) were evaluated in order to achieve clinical and dermoscopic diagnoses. Statistical analyses were performed with the chi2-test and Fisher's exact test, when appropriate.
Results: The most frequent and significant clinical features for TnM and TkM were asymmetry and ulceration (the latter only for TkM) compared with AHBML. Irregular dots/globules (62% vs. 35%; P
Conclusions: Because dermoscopy uses criteria reflecting pigmentation (irregular pigmentation and irregular dots/globules) and vascular patterns, it is a useful technique not only for pigmented melanoma but also for hypomelanotic melanoma. In 'truly' AM, vascular patterns alone may not be sufficient to diagnose melanoma. A combined approach with the clinical information should help in the detection of 'truly' AM.