Dermatology: Practical and Conceptual


Image Letter | Dermatol Pract Concept. 2024;14(2):e2024064 1

A Lesion Surrounded by the Rainbow: 
Merkel Cell Carcinoma

Melek Aslan Kayıran1, Ahmet Sait Şahin1, Bengu Cobanoglu Simsek²

1 Department of Dermatological and Venereal Diseases, İstanbul Medeniyet University, Göztepe Prof. Dr. Süleyman Yalçın City Hospital, 

Istanbul, Turkey

2 Department of Pathology, İstanbul Medeniyet University, Göztepe Prof. Dr. Süleyman Yalçın City Hospital, Istanbul, Turkey

Citation: Kayıran MA, Şahin AS, Simsek BC. A Lesion Surrounded by the Rainbow: Merkel Cell Carcinoma. Dermatol Pract Concept. 
2024;14(2):e2024064. DOI: https://doi.org/10.5826/dpc.1402a64

Accepted: October 22, 2023; Published: April 2024

Copyright: ©2024 Kayıran 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: Melek Aslan Kayıran, Eğitim Mah. Kadıköy/İstanbul 34722 E-mail: melekaslan@gmail.com

Case Presentation

A 76-year-old male presented due to a mass on his left leg, 

which had appeared three months earlier. A firm 1 cm purple 

nodule was observed on the left thigh. In addition, an ery-

thematous macule measuring approximately 10 cm in diam-

eter around the nodule was seen (Figure 1A). Dermoscopy 

of the nodule revealed scattered linear telangiectasias in the 

center, whitish-red areas, a rainbow pattern surrounding the 

lesion, and scales (Figure 1B). Histopathological examina-

tion showed a tumor with a nodular growth pattern in the 

dermis composed of cells with a high nucleus-to-cytoplasm 

ratio, round-oval nuclei, and finely dispersed chromatin. 

The neoplastic cells exhibited positivity for cytokeratin-20 

and neuroendocrine tumor markers. Merkel cell carcinoma 

(MCC) was diagnosed and was completely excised, with 

negative regional lymph nodes. Three months later, a biopsy 

of a mass detected on the right lumbar region was reported 

as renal cell carcinoma, leading to nephrectomy. The patient 

is regularly monitored, and no recurrence or new lesion has 

been detected.

Teaching Point

Although the rainbow pattern on dermoscopy is primarily 

associated with Kaposi sarcoma, it has also been reported 

in lesions such as pyogenic granuloma, strawberry heman-

gioma, malignant melanoma, angiokeratoma, basal cell 

 carcinoma, dermatofibroma, and blue nevus [1]. However, a 

few MCC cases have only previously described the rainbow 

pattern [2,3]. Merkel cell carcinoma is a rare carcinoma with 

a poor prognosis due to its high, rapid metastasis potential. 

Therefore, MCC should also be considered when encounter-

ing a rapidly growing purplish solitary mass with a rainbow 

pattern on dermoscopy.



2 Image Letter | Dermatol Pract Concept. 2024;14(2):e2024064

References

1. Draghici C, Vajaitu C, Solomon I, et al. The Dermoscopic Rain-

bow Pattern - A Review of the Literature. Acta Dermatovenerol 

Croat. 2019;27:111–115. 

2. di Meo N, Vernoni S, Longone M, Trevisan G. Image  Gallery: 

Merkel cell carcinoma under the rainbow. Br J Dermal. 2017; 

177:e166. doi: 10.1111/bjd.15815. 

3. Scalvenzi M, Palmisano F, Ilardi G, et al. Clinical, dermoscopic 

and histological features of a Merkel cell carcinoma of the hand. 

J Dermatol Case Rep. 2013;7:15.

Figure 1. A) Firm purplish nodule on the right thigh surrounded by an 

 erythematous macule. B) The dermoscopic view: multiple telangiectatic vessels, 

some of which branched, and the rainbow pattern surrounding the purple nodule.  

C) The tumor localized in the dermis is composed of neuroendocrine cells 

(HEX100). D) Positive staining with neuroendocrine markers in Merkel cell carci-

noma (SynaptophysinX200).