Characteristics of exogenous pigment diseases under reflectance confocal microscopy

Dear Editor,

Exogenous pigment diseases usually include artificially required skin tattoos, such as tattoos, ¹ , ² eyebrow tattoos, and post‐traumatic foreign body implants caused by various accidents, such as the marks formed when pencil lead accidentally pierces the skin. The characteristics of reflectance confocal microscopy (skin CT) for exogenous pigment diseases have not been reported yet.

Recently, in clinical work, we summarized the characteristics of reflectance confocal microscopy of exogenic pigmentary diseases, hoping to help clinical dermatologists in diagnosis and treatment. Now I will share the details with you.

First, let's look at the first patient. As shown in Figure 1A, a light brown pigmented nevus (white circle) can be seen near the eyebrow arch on the inner side of the right upper eyelid of the patient, protruding from the surface of the skin. Through skin CT examination, it is considered to be diagnosed as an intradermal nevus. The microscopic feature is that the basal cell ring is generally normal, and large high‐refraction nevus cells can be seen in the superficial and middle dermis, some of which are fused into a mass, with a nest distribution (Figure 1B). Through Figure 1A, we can also find that the patient's eyebrow arch left traces behind the original eyebrow tattoos (red circle), so when conducting a skin CT examination, we inadvertently found its microscopic features: 1. The epidermis was generally normal (Figure 1C); 2. A large number of highly refractive pigment particles can be seen scattered in the superficial and middle layers of the dermis, with different sizes, irregular borders, and disorderly arrangement, just like the twinkling stars in the night sky, some of which are fused into a large area (Figure 1D,E).

FIGURE 1.

(A) The patient's clinical picture shows 1 pigmented nevus (white circle) and traces left behind the eyebrow tattoos. (red circle). (B) CT features of intradermal nevus: high refraction nevus cell mass and nest‐like distribution can be seen in the dermis. (white arrow and red circle). (C) The epidermis is generally normal. (D) A large amount of high‐refractive pigment particles in the superficial dermis (white arrow). (E) Some pigment granules infiltrated deeper into the middle dermis (white arrow).

Next, the second patient was a child. As shown in Figure 2A, the patient's hip was accidentally pierced by a pencil lead to form a blue‐black mark (red circle), with a light red halo around it. We examined the mark with a reflectance confocal microscope and found that its CT features were basically consistent with eyebrow tattoos under the RCM:1. The epidermis was basically normal (Figure 2B); 2. There are many irregularly arranged high‐refractive pigment granules in the superficial and middle layers of the dermis, with different sizes, unclear boundaries, deep infiltration in some areas, and no obvious heteromorphism (Figure 2C,D). Through such skin CT features, it is helpful for us to differentiate it from pigmented nevus.

FIGURE 2.

(A) Skin lesions (white circle) formed after the patient's buttocks were punctured by pencil lead. (B) The epidermis is generally normal. (C) High refractive pigment granules scattered in the superficial dermis (white arrow). (D) More high‐refractive pigment particles can be seen in the middle layer of the dermis, and the volume is larger (white arrow).

Finally, a young man with a tattoo on his back (Figure 3A) was also examined by a reflectance confocal microscope. It was found that his microscopic features were basically the same as those of the above two people: 1. No abnormality was found in the epidermis (Figure 3B); 2. A large number of high‐refraction phagocytic pigment cells and pigment granules can be seen in the superficial dermis, ³ which are different in size and disordered in arrangement (Figure 3C). Some pigment granules are deeply infiltrated (Figure 3D).

FIGURE 3.

(A) Tattoo image of the patient's back. (B) The epidermis is generally normal. (C) A large number of hyper‐refractive pigment granules and phagocytes in the superficial dermis (white arrow). (D) Part of the pigment particles infiltrated deeper into the middle dermis (white arrow).

At the same time, we performed a histopathological examination on the tattoo of this patient, and its pathological characteristics were: free blue‐black pigment granules could be seen in the middle and upper dermis (Figure 4A). Such histopathological findings are highly consistent with its skin CT features. The blue‐black pigment granules in histopathology correspond to the hyper‐refractive pigment granules in skin CT (Figure 4B).

FIGURE 4.

(A) More free blue‐black pigment particles (black arrows) in the middle and upper dermis (HE staining ×10). (B) More high refractive pigment particles in the superficial and middle dermis (white arrow).

Through the above sharing, it is not difficult to find that the skin CT features of exogenous pigmented diseases ⁴ mainly show that a large number of high refractive pigment particles and phagocytes appear in the superficial and middle dermis, with different sizes and shapes and irregular arrangement (Figure 5A,B). Such microscopic features are basically consistent with their histopathological (Figure 5C) manifestations.

FIGURE 5.

(A, B) A large number of high refractive pigment granules and phagocytes in the superficial and middle dermis, with different sizes, shapes, and irregular arrangements (red circle). (C) A large amount of blue‐black pigment particles in the middle and upper part of the dermis (HE staining×40).

I hope this sharing will be beneficial to clinicians, helping them understand the skin CT features of exogenous pigment diseases and differentiate them from other diseases.

DATA AVAILABILITY STATEMENT

The data that support the findings will be available in CNKI at www.cnki.net following an embargo from the date of publication to allow for the commercialization of research findings.