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Dermatofibromas are benign skin lesions that consist of pigmented papules or nodules. They produce the dimple sign when laterally squeezed and are usually found on the legs. These clinical features lead to the diagnosis in most cases. However, the differential diagnosis with other lesions, such as atypical nevi and melanoma can be difficult, and the dermoscopy may help the diagnosis. There are several dermoscopic patterns associated with dermatofibromas, the most common being a central white scar like patch with delicate pigment network at the periphery. This article describes the case of a patient who had eleven clinically similar dermatofibromas, with four distinct patterns when submitted to dermoscopic examination.
What was known?
Dermatofibromas are non-melanocytic lesions which may present with pigment network, such as seborrheic keratosis and supernumerary nipple. These lesions are considered an exception to the rule since the presence of such pigment network is a criterion for melanocytic lesions. The classical pattern associated with dermatofibromas is a central white scar like patch and a peripheral pigment network.
Dermatofibroma is a benign skin lesion, characterized by a reactive fibroblastic proliferation of the skin, usually secondary to minor trauma or insect bites.
Clinically, it consists of a firm asymptomatic nodule or papule, 3 to 20 mm in size, with variable colors. Dermatofibroma exhibits the Fitzpatrick's dimple sign when laterally compressed. This skin tumor usually persists indefinitely, affecting mainly young adults with a slight predilection for females. It may appear as single or multiple lesions and is usually found on the lower limbs.
The epidermis is usually hyperplastic with hyperpigmentation of the basal layer and elongated epidermal ridges. There is a proliferation of fibroblast-like spindle cells in the dermis, separated from the upper epidermis by a Grenz zone.[4,5]
The diagnosis of dermatofibroma is usually easy because of its clinical appearance. However, the differentiation of dermatofibroma from other skin tumors can be difficult in some cases, especially when the lesion presents atypically or is a rare subtype. In these cases, it can simulate atypical nevi or melanoma and dermoscopy may improve diagnostic accuracy and assist in the exclusion of malignant lesions.[6,7]
The dermoscopic pattern classically associated with dermatofibromas consists of a white scar like patch and delicate pigment network at the periphery.[8,9] However, a recent review of the literature showed that this type of skin tumor can present a variety of dermoscopic patterns.[2,3,9] We report the case of a healthy patient who had eleven dermatofibromas with four distinct dermoscopic patterns.
A 41-year-old healthy woman presented to us with a history of multiple asymptomatic brownish skin lesions for 20 years.
Eleven clinically similar papular-nodular brownish lesions with a smooth surface, ranging from 5 to 10 mm in diameter, were found during the dermatological examination. These nodules were noticed on the trunk, buttocks and lower limbs [Figure 1].
The lesions were indexed and photographed with a digital camera attached to dermoscope and the images stored in order to be evaluated and compared in the future. Dermoscopy with polarized light was performed using the DermLite DL3 dermoscope (Photo DermLite, 3GenLLC, Dana Point, Calif.). All lesions were surgically removed and showed similar histopathological findings consistent with the cellular subtype of dermatofibroma [Figure 2]. Clinical evaluation and laboratory tests for immunosuppression were negative.
The dermoscopic patterns of the eleven lesions were evaluated and classified into four different groups. The main pattern (4 lesions, 36.3%) associated with this patient was the delicate peripheral pigment network with central globule like structures [Figure 3]. The second group (3 lesions, 27.2%) in frequency was dermatofibromas with irregular crypts and pseudofollicular openings [Figure 4]. The third observed pattern (3 lesions, 27.2%) had an area of homogeneous pigmentation in the entire lesion [Figure 5]. Finally, the fourth group (1 lesion, 9.0%) consisted of a single lesion with atypical dermoscopic pattern [Figure 6]. A central irregular white scar like patch with pseudofollicular openings and a peripheral erythematous homogeneous macule was noticed.
A recent review of the literature showed that dermatofibromas can present ten specific dermoscopic patterns. Dermatofibromas with peripheral delicate pigment network include patterns with pigment network located throughout the entire lesion or at the periphery, either with a white scar like patch, white network or homogeneous pigmentation at the center. On the other hand, dermatofibromas without peripheral delicate pigment network include patterns with white network or homogeneous pigmentation throughout the lesion, total scar like patch, peripheral homogeneous pigmentation with either a white scar like patch or a white network at the center, and atypical pattern.
Most of the literature on dermoscopy of dermatofibromas is based on non-polarized dermoscopy. However, the present study used non-contact polarized light dermoscopy, a more recent technique that combines convenience and image quality. It also improves visibility of vascular structures by avoiding compression of the skin by a glass contact plate.
All four dermoscopic patterns observed in this study were consistent with specific patterns already described in the literature, such as delicate peripheral pigment network with central globule like structures, irregular crypts and pseudofollicular openings, homogeneous pigmentation in the entire lesion and atypical pattern.
Although dermatofibromas have a wide range of dermoscopic aspects, the main pattern found in this patient was the delicate peripheral pigment network with central globule like structures, in agreement with recent findings in the literature showing that the combination of these structures appears rather frequently.[3,6]
The presence of a pigmented network is an important dermoscopic pattern in differentiating melanocytic and non-melanocytic lesions. Dermatofibroma, seborrheic keratosis and supernumerary nipple are an exception to this rule. Dermatofibromas are thus considered non-melanocytic lesions with brown, fine and delicate pigment network, often extending gradually toward the adjacent healthy skin. The peripheral pigment network of dermatofibromas is usually a result of hyperpigmentation of basal layer cells. The globule like structures are visualized because the rete ridges are usually flat, confluent and hyperpigmented.[2,3]
The second and third dermoscopic patterns appeared equally in frequency and consisted of an area of total homogeneous pigmentation and irregular crypts associated with pseudofolicular openings, respectively. The pattern of irregular crypts corresponds histologically to areas where the epidermis is slightly hyperplastic with multiple superficial keratin plugs. As for the pseudofolicular openings, they represent small horny intraepidermal cysts in contact with the surface. Correlation between the dermatoscopic and histopathologic features of the non-melanocytic skin tumors has not been a highly studied area of dermatoscopy practice.[7,9]
The atypical pattern consisted of a central irregular white scar like patch with pseudofollicular openings and a peripheral erythematous homogeneous macule. The presence of erythema or small vessels, especially when associated with a multicomponent pattern, should draw attention to the differential diagnosis with vascular tumors and malignant lesions.[2,8] In these cases, surgical removal of the lesion should be performed and the material sent for histopathological examination.
This article emphasizes the importance of a well-performed and interpreted dermoscopy on the establishment of clear criteria for the diagnosis of non-melanocytic lesions, such as dermatofibroma. A wide range of dermoscopic patterns of dermatofibroma has already been described on the literature. However, more studies need to be conducted regarding the correlation of dermoscopic and histopathologic aspects of dermatofibromas and other non-melanocytic lesions.
What is new?
A wide range of dermoscopic faces of dermatofibroma has recently been described on the literature, including atypical patterns. The multicomponent pattern should draw attention to the differential diagnosis with vascular tumors and malignant lesions, such as melanoma. The establishment of clear dermoscopic criteria for dermatofibromas may improve the diagnosis.
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Conflict of Interest: Nil.