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. 2025 Dec 12.
doi: 10.1111/ijd.70213. Online ahead of print.

Dermoscopy in Merkel Cell Carcinoma-A Multicenter Retrospective Study of the International Dermoscopy Society

Katarzyna Korecka  1 , Iulia Maria Badiu  2 , Philipp Tschandl  3 , Bengü Nisa Akay  4 , Zoe Apalla  5 , Rainer Hofmann-Wellenhof  6 , Harald Kittler  3 , Noa Kremer  7   8 , Sven Lanssens  9 , Caterina Longo  10 , Satish Frank Kishore Lubeek  11 , Ashfaq Marghoob  7 , Christoph Mueller  3 , Christiane Mutz-Rabl  6 , Cristian Navarrete-Dechent  12 , John Paoli  13   14 , Felix Khoa Pham  15   16   17 , Mahtab Samimi  18 , Marco Spadafora  10 , Luc Thomas  15   16   17 , Yaei Togawa  19 , Pablo Vargas-Mora  20 , Aimilios Lallas  21
Affiliations

Dermoscopy in Merkel Cell Carcinoma-A Multicenter Retrospective Study of the International Dermoscopy Society

Katarzyna Korecka et al. Int J Dermatol. .

Abstract

Background: Merkel cell carcinoma (MCC) is a rare neuroendocrine tumor that usually presents as a pink nodule on sun-exposed skin in elderly patients. This study aimed to investigate the dermoscopic patterns of MCC and identify predictors that may help distinguish it from other benign or malignant tumors often included in its differential diagnosis.

Methods: This was a study announced via an online call on the International Dermoscopy Society website where we collected macroscopic and dermoscopic images of MCC and other tumors with similar clinical morphology that served as controls. Sixteen experts were asked to assess the images for the presence of preselected dermoscopic features. Univariable feature analysis, multivariable logistic regression analysis, and interrater reliability assessment were performed.

Results: In total, 402 cases were collected: 134 MCCs and 268 controls. Three hundred and ninety six images were included in the analysis after the exclusion of poor-quality photographs. Pink color was the most common feature in MCC (92.4%, 95% confidence interval [CI]: 1.17-5.7), followed by white color (58%, 95% CI: 0.62-1.51) and linear irregular vessels (43.5%, 95% CI: 0.61-1.47). Scale on the surface was documented in 33.6% of MCCs compared to 23.4% of controls (95% CI: 1.01-2.69). Multivariable logistic regression analysis identified two positive predictors of MCC, namely pink color and scale, and three negative predictors, namely ulceration, brown, and blue-gray pigmentation.

Conclusion: MCC might mimic other benign or malignant lesions. In nonpigmented tumors dermoscopically characterized by pink color and scales, MCC should be prioritized among the differentials.

Keywords: Merkel cell carcinoma; dermoscopy; differential diagnosis.

Plain language summary

The dermoscopic features of MCC have been described in case series and case reports and include a polymorphous vascular pattern consisting of linear irregular, arborizing, glomerular, and dotted vessels, a milky red background, and shiny or non‐shiny white areas. This was a multicenter retrospective study which was announced via an online call on the International Dermoscopy Society (IDS) website and social media. Contributors were asked to submit cases of MCC and other clinically similar tumors to be used as controls. Throughout the evaluation, we found two positive indicators of MCC: pink color (p = 0.036) and scales (p = 0.016), and three negative predictors: blue‐gray pigmentation (p = 0.012), brown color (p = 0.025), and ulceration (p = 0.007). Since MCC is usually a nonpigmented tumor, this study suggests that pink color and scales may serve as supportive diagnostic criteria for MCC.

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References

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