Dermatology: Practical and Conceptual


Image Letter | Dermatol Pract Concept. 2024;14(3):e2024208 1

The Importance of Polarized and Non-Polarized 
Light in the Dermoscopic Assessment of Amelanotic 

Melanoma: A Teaching Case
Vittorio Tancredi1, Pierfrancesco Benvenuto1, Luca Damiani1, Camila Scharf1,  

Elvira Moscarella1, Giuseppe Argenziano1

1 Dermatology Unit, Department of Mental and Physical Health and Preventive Medicine, University of Campania Luigi Vanvitelli, Naples, 

Italy

Citation: Tancredi V, Benvenuto P, Damiani L, Scharf C, Moscarella E, Argenziano G. The Importance of Polarized and Non-Polarize Light 
in the Dermoscopic Assessment of Amelanotic Melanoma: A Teaching Case. Dermatol Pract Concept. 2024;14(3):e2024208. DOI: https://
doi.org/10.5826/dpc.1403a208

Accepted: April 13, 2024; Published: July 2024

Copyright: © Tancredi et al. This is an open-access article distributed under the terms of the Creative Commons Attribution-
NonCommercial License (BY-NC-4.0), https://creativecommons.org/licenses/by-nc/4.0/, which permits unrestricted noncommercial use, 
distribution, and reproduction in any medium, provided the original authors and source are credited.

Funding: None.

Competing Interests: None.

Authorship: All authors have contributed significantly to this publication.

Corresponding Author: Vittorio Tancredi, MD, Dermatology Unit, Department of Mental and Physical Health and Preventive Medicine, 
University of Campania Luigi Vanvitelli, Via Sergio Pansini, 5, 80131 Naples, Italy; phone: +39 3313919797; fax: +39 0815468759;  
Email: tancredivittorio@ymail.com

Case Presentation

A 77-year-old woman was referred to our department for a 

large new growing pink nodule on her left arm ( Figure 1A-B).  

The initial clinical diagnoses included basal cell carcinoma 

(BCC), dermatofibroma, dermal nevus, and melanoma; 

however, dermoscopy did not show clear criteria of BCC or 

other benign lesions. Therefore, urgent excision was deemed 

necessary to rule out amelanotic melanoma. The histolog-

ical diagnosis confirmed a nonulcerated 2.8 mm Breslow 

thickness invasive melanoma (IM). Dermoscopic evaluation 

of the lesion was performed using both polarized and non- 

polarized light.

Teaching Point

Under polarized light (PL), on a pinkish background, the le-

sion exhibited prominent shiny white structures, which made 

it possible to exclude dermal nevus but not BCC or IM [1]. 

Conversely, non-polarized light (NPL) highlighted diffuse 

atypical vessels, mostly linear-irregular and definitely not ar-

borizing, as expected for BCC (Figure 1C-D). NPL cannot 

show shiny white structures; however, it facilitated a clearer 

observation of the vascularization as this was not obscured 

by the white structures themselves, and, in general, is valid in 

highlighting more superficial structures. As amelanotic mela-

noma is often a featureless tumor, using dermoscopic devices 



2 Image Letter | Dermatol Pract Concept. 2024;14(3):e2024208

allowing both the light modalities should be preferred by 

dermatologists as they increase diagnostic accuracy and the 

differential diagnosis with clinical imitators.

References

1. Liebman TN, Rabinovitz HS, Dusza SW, Marghoob AA. White 

shiny structures: dermoscopic features revealed under polarized 

light. J Eur Acad Dermatol Venereol. 2012 Dec;26(12):1493-7. 

doi: 10.1111/j.1468-3083.2011.04317.x. Epub 2011 Oct 31. 

PMID: 22035217.

Figure 1. A and B clinical pictures of a pink nodule on sun-damaged skin. C shows dermatoscopic evalua-

tion with polarized light: shiny white structures are the prominent features. D shows dermatoscopic evalu-

ation with non-polarized light: