Dermatology: Practical and Conceptual


Letter  |  Dermatol Pract Concept 2020;10(4):2020070 1

Dermatology Practical & Conceptual

Introduction

Pigmented epithelioid melanocytoma (PEM) is an uncommon 

and recently described entity with unknown biologic 

behavior. It is a melanocytic tumor showing overlapping 

features of both an atypical epithelioid blue nevus and a low-

grade “animal-type melanoma.”

PEM occurs over a broad age range, with a predilection 

for children and young adults, and clinically appears as 

a macular, popular, or nodular lesion. Dermoscopically, 

PEM appears as a polymorphic lesion, characterized by 

homogeneous blue pigmentation and a combination of 

black, brown, and white colors. Histopathologically, it is 

characterized by a dermal proliferation of heavily pigmented, 

both dendritic and spindle/epithelioid melanocytes, admixed 

with slightly larger, plumper, and less pigmented epithelioid 

cells [1]. Involvement of the regional nodes has been 

reported but usually with no further spread of the disease. 

No histological criteria are predictive of metastatic behavior. 

Case Presentation

We describe a case of vulvar mucosal PEM, that occurred 

on the right small lip of a 50-year-old woman. Clinically it 

appeared as an intensely pigmented, brown-black papule 

about 1 cm in size. On dermoscopy, we observed many 

irregular, black blotches surrounded by a whitish blue 

veil. No atypical vascular feature was detected. Due to its 

globular structure and black-bluish color and considering 

the age of the patient and rapid onset, the lesion resembled 

a Spitz nevus or an atypical Spitz tumor (Figure 1, A and B). 

However, spitzoid lesions do not show these dermoscopic 

features. Therefore, an excisional biopsy was performed. 

The histological examination showed an acanthotic 

epidermis with a slightly warty profile overlying a large 

dermal nodular lesion with blurred borders consisting of 

hyperpigmented epithelioid and spindle dendritic melanocytes 

arranged in perivascular and periadnexal bundles, mixed 

with epithelioid nevoid cells and numerous melanophages. 

No significant atypia, mitosis, or necrosis was appreciated. 

A Case of a Pigmented Epithelioid Melanocytoma 
on a Mucosal Site

Alice Ramondetta1, Simone Ribero1, Luca Conti1, Pietro Quaglino1, Paolo Broganelli1

1 Dermatology Clinic and Surgical Pathology Section, Department of Medical Sciences, University of Turin, Italy

Key words: melanocytoma, epithelioid cells, vulva, genital dermatopathology, melanocytic lesion

Citation: Ramondetta A, Ribero S, Conti L, Quaglino P, Broganelli P. A case of a pigmented epithelioid melanocytoma on a mucosal site. 
Dermatol Pract Concept. 2020;10(4):e2020070. DOI: https://doi.org/10.5826/dpc.1004a70

Accepted: April 21, 2020; Published: October 26, 2020

Copyright: ©2020 Ramondetta et al. This is an open-access article distributed under the terms of the Creative Commons Attribution 
License BY-NC-4.0, which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original 
author and source are credited.

Funding: None.

Competing interests: The authors have no conflicts of interest to disclose.

Authorship: All authors have contributed significantly to this publication.

Corresponding author: Simone Ribero, MD, PhD, Dermatology Clinic, Department of Medical Sciences, University of Turin,  
via Cherasco 23, 10126,  Italy. Email: simone.ribero@unito.it 



2 Letter  |  Dermatol Pract Concept 2020;10(4):2020070

and malignant lesions, from which it must be distinguished, 

albeit with difficulty.

References

1. Moscarella E, Ricci R, Argenziano G, et al. Pigmented epithelioid 

melanocytoma: clinical, dermoscopic and histopathological 

features. Br J Dermatol. 2016;174(5):1115-1117. https://doi.

org/10.1111/bjd.14322. PMID:26614732.

2. Uehara M, Sato S, Kato A, et al. A rare case of pigmented 

epithelioid melanocytoma on the penis as a divided nevus. 

Eur J Dermatol. 2014;24(2):248-249. https://doi.org/10.1684/

ejd.2014.2272. PMID:24723648.

Immunohistochemical staining was performed. While HMB-

45 and Melan-A were positive, p16 was expressed on the 

entire lesion, and KI-67 showed low activity (1%) (Figure 

2, A and B). 

Conclusions

Pigmented lesions of mucosal sites usually can be difficult to 

interpret. PEM is a rare entity, and we report on a case of 

a female genital mucosal variant. Uehara et al published a 

case of PEM on the glans [2]. PEM could mimic both benign 

Figure 1. (A) Clinical appearance: oval papule, brown-black in color, intensely pigmented, about 1 cm in size. (B) Dermoscopy: many irregu-

lar, black blotches surrounded by a whitish blue veil. No atypical vascular feature was detected.

Figure 2. (A) Histopathological specimen: acanthotic epidermis with a slightly warty profile overlying a large dermal nodular lesion with 

blurred limits consisting of hyperpigmented epithelioid and spindle dendritic melanocytes arranged in perivascular and periadnexal bundles, 

mixed with epithelioid nevoid cells and numerous melanophages. No significant atypia, mitosis, or necrosis was appreciated. Immunohis-

tochemical staining: HMB-45, Melan-A (B) and p16 (all expressed), KI-67 (1%).

A B

A B