Dermatology: Practical and Conceptual


Image Letter | Dermatol Pract Concept. 2024;14(4):e2024234 1

Exogenous Pigmentation by Foreign Body Under 
Reflectance Confocal Microscopy Mimicking 

Recurrence of Lentigo Maligna
Piscazzi Francesco1,2, Di giulio Sara1,2, Ardigò Marco1,2

1 Dermatology Unit, IRCCS Humanitas Research Hospital, Rozzano (MI), Italy

2 Department of Biomedical Sciences, Humanitas University, Pieve Emanuele (MI), Italy

Key words: Confocal reflectance microscopy, Lentigo maligna, Mimicker, Foreign bodies

Citation: Piscazzi F, Di Giulio S, Ardigò M. Exogenous Pigmentation by Foreign Body Under Reflectance Confocal Microscopy Mimicking 
Recurrence of Lentigo Maligna. Dermatol Pract Concept. 2024;14(4):e2024234. DOI: https://doi.org/10.5826/dpc.1404a234

Accepted: June 9, 2024; Published: October 2024

Copyright: ©2024 Piscazzi 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: Piscazzi Francesco, MD, Dermatology Unit, IRCCS Humanitas Research Hospital, Rozzano (MI);  
Department of Biomedical Sciences, Humanitas University, Pieve Emanuele (MI), Italy. Via Alessandro Manzoni, 56, 20089 Rozzano MI; 
Email: francesco.piscazzi@humanitas.it

Case Presentation

A 76-year-old woman visited our clinic with an oval neoforma-

tion at the base of her nose, which was dermoscopically suspected 

for lentigo maligna (LM). A conventional surgical excision 

followed by histological examination confirmed LM without 

involvement of the surgical margin, with three millimeters  

to the nearest margin. Six months post-operation, during a 

routine follow-up, a blue-grayish pigmentation was observed 

on the nasal scar (Figure 1A). Further dermoscopic analysis 

revealed a white surgical scar surrounded by a blue-grayish 

pigmentation (Figure 1B). The patient reported a nasal bone 

contusion and fracture four months earlier due to a fall. To 

address the nature of the pigmentation, reflectance confocal 

microscopy (RCM) was conducted, aiming to either rule out 

LM’s persistence beneath the scar or detect any post-trauma 

exogenous pigmentation. RCM findings included a normal 

honeycomb pattern in the spinous granular layer (not shown) 

and densely packed hyperreflective granules  (Figure 1C and 

1D) within the epidermis and dermis, indicative of exogenous 

pigmentation [1]. There were no clear signs of LM such as 

pagetoid cells, folliculotropic atypical cells, or atypical nest at 

the dermo-epidermal junction or in the dermis [2]. The final 

diagnosis pointed to exogenous pigmentation by asphalt.

Teaching Point

Under RCM examination, exogenous pigmentation from 

foreign bodies is characterized by densely packed hyperre-

flective granules in the epidermis and dermis, lacking the 

RCM features typically seen in pigmented tumors. RCM is 

crucial for differentiating between pigmentary skin disorders 

like melanocytic nevi, superficial spreading and lentigo ma-

ligna melanoma, seborrheic keratosis, pigmented actinic ker-

atosis, and basal cell carcinomas, offering the advantage of 

diagnosing without performing surgical biopsy.



2 Image Letter | Dermatol Pract Concept. 2024;14(4):e2024234

References

1. Sun H, Duan Y, Zhao J, Li R. Characteristics of exogenous 

 pigment diseases under reflectance confocal microscopy. Skin 

Res Technol. 2023;29(5):e13318. DOI:10.1111/srt.13318.

2. Cinotti E, Labeille B, Debarbieux S, et al. Dermoscopy vs. 

 reflectance confocal microscopy for the diagnosis of lentigo 

 maligna. J Eur Acad Dermatol Venereol. 2018;32(8):1284-1291. 

DOI:10.1111/jdv.14791.

Figure 1. (A) Clinical picture showing a pigmented scar on the nasal bridge. (B) Dermoscopic 

picture showing a grayish-blue structureless area that encircles the white surgical scar. Reflectance 

confocal microscopy examination revealed many irregularly arranged, highly refractive pigment 

granules (red arrows) in the (C) epidermis and the (D) dermis, varying in size and with distinct 

boundaries but lacking the characteristics of lentigo maligna.