Multiple agminated lesions with homogeneous blue pattern on dermoscopy

Case Report

The case presents a Caucasian female, who had been consulting dermatology for nine years for asymptomatic lesions on the central thorax, present from the first days of life. On physical examination, multiple brown and skin-colored papules were observed 2–3 mm in size (Figure 1). With dermoscopy (polarized light), the lesions showed an agminated homogeneous blue pattern (Figure 2) and a pore, through which brown material was seen (Figure 3).

Figure 1.

Clinical image. Multiple brown and skin-colored papules on the anterior chest. [Copyright: ©2017 Lozano-Masdemont.]

Figure 2.

Dermoscopy (polarized light). Agminated homogeneous blue pattern resembling a bunch of grapes (bunch of grapes sign) and a schematic representation of the image. [Copyright: ©2017 Lozano-Masdemont.]

Figure 3.

Dermoscopy (polarized light). (a) Isolated pore (keratin-filled orifice). (b) A pore and a papule with homogeneous blue pattern (arrow). [Copyright: ©2017 Lozano-Masdemont.]

Discussion

A biopsy, covering three lesions, showed three cystic formations in the middle dermis, covered by squamous epithelium, the interior of which contained laminated keratin and multiple vellus hairs (Figures 4, 5). The diagnosis of eruptive vellus hair cyst (EVHC) was established.

Figure 4.

Histopathologic image. A cystic formation in the middle dermis covered by squamous epithelium, the interior of which contained trichilemmal keratinization and multiple vellus hairs (hematoxylin and eosin, 20x). [Copyright: ©2017 Lozano-Masdemont.]

Figure 5.

Histopathologic image. Detail (hematoxylin and eosin, 40x). [Copyright: ©2017 Lozano-Masdemont.]

EVHC are asymptomatic skin-colored papules, erythematous or bluish, typically located in the anterior portion of the chest, axillae and buttocks. It usually occurs in children, even from birth, as in the case presented, which is postulated to be a hamartomatous entity. Histologically, they are characterized by dermal cystic formations of squamous epithelium, laminated keratin and multiple vellus hairs. The dermoscopic characteristics of EVHC have been described only twice, with different findings. Alfaro-Castellón et al describe them as round or oval yellowish structures, with occasional erythematous halos [1]. In our case, the lesions show a homogeneous blue pattern, agminated, so the dermoscopic image resembles a bunch of grapes (bunch of grapes sign). The main differential diagnoses of the homogeneous blue pattern are blue nevus and melanoma metastasis, although in recent years other lesions, mostly adnexal, are being described with this pattern, caused by the Tyndall effect. Trichilemmal cysts may show a erythematous periphery, besides the homogeneous blue pattern [2]. Ectopic hidradenoma papilliferum may present large vessels in the periphery [3]. Eccrine acrospiroma is surrounded by a discrete pigment network [4], like some dermatofibromas [5].

Oiso et al [6] observed another dermatoscopic sign: cystic openings in the epidermis, a feature that can also be seen in Figure 3 of this case. These or puncta barely visible to the naked eye can also be observed in epidermal cysts, although these do not exhibit the characteristic bluish agminated structures (Figure 3b) or clinical location. Finally, with dermoscopy, common acne shows yellowish or brownish follicular plugging and inflammation [1].

Dermoscopy may be a useful tool in the diagnosis of these lesions, especially at atypical locations or ages, besides being a safe technique, which could have been used in this patient since birth.