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Case Report Compound Nevus Mimicking a Seborrheic : A Keratotic without Any Dermoscopic Criteria for a Melanocytic

Işıl Kılınç Karaaslan,1* MD, Taner Akalın,2 MD, Fezal Özdemir,1 MD

Address: 1Department of and 2Department of Pathology, Ege University Medival Faculty, Bornova, İz- mir, 35100, Turkey E-mail: [email protected] * Corresponding author: Işıl Kılınç Karaaslan, MD, Ege University Medical Faculty Department of Dermatology, Bornova, İzmir, 35100, Turkey

Published: J Turk Acad Dermatol 2008; 2 (3): 82301c This article is available from: http://www.jtad.org/2008/3/jtad82301c.pdf Key Words: nevus, keratotic melanocytic nevus, dermoscopy,

Abstract

Observations: We report an exceptional case of a compound nevus in which none of the criteria described for a melanocytic lesion was observed on dermoscopy. The lesion was a keratotic com- pound nevus and this case demonstrated that diagnosis of a keratotic melanocytic nevus might be difficult both clinically and dermoscopically.

Introduction vealed none of the criteria for a melanocytic le- sion (pigment network, aggregated globules, Compound nevus is a common melanocytic streaks or homogeneous blue pigmentation). lesion which demonstrates both junctional Considering the young age of the patient, the le- nests and intradermal . It is sion was excised to explore melanocytic/non- generally seen as a or plaque with a melanocytic nature of the lesion with the preop- smooth surface, uniform border and pig- erative diagnosis of a seborrheic keratosis. Histo- pathologically, epidermal and hy- mentation. It exhibits a pigment network perkeratosis, multiple keratotic plugs between and brown globules distributed regularly on the digitiform papillations formed by papilloma- dermoscopy. Rarely, milia-like cysts and co- tosis, and horn pseudocysts were seen together medo-like openings can also be observed, with nevus cell nests both in the dermal/ although these two are the characteristic epidermal junction and the . Junctional dermoscopic features of seborrheic kerato- nests were mostly right beneath the keratotic sis [1]. plugs and horn pseudocysts (Figure 1b). The di- agnosis was a keratotic compound nevus. We report a case of a compound nevus with dermoscopic features difficult to differenti- ate from seborrheic keratosis. Discussion

Case Report The two-step algorithm should be followed in the dermoscopic classification of pig- The lesion was a light-brown pigmented plaque mented . In the first step which which was 14 x 4 mm in diameter on the neck of a 16-year-old female. On dermoscopy, multiple differentiates a melanocytic versus non- comedo-like openings distributed extensively melanocytic lesion, pigment network, aggre- throughout the lesion and some milia-like cysts gated globules, streaks or homogeneous were seen (Figure 1a). Careful examination re- blue pigmentation should be searched. If

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Figure 1. (a) Extensively distributed comedo-like openings (red arrows) and a few milia-like cysts (black arrows) on dermoscopy. Inset: Light-brown pigmented plaque on the neck. (b) Low power view of the lesion characterized by papillomatosis, hyperkeratosis, horn pseudocysts and nevus cells (HE x 40). these criteria characteristic for a melano- other clinical diagnoses of nevi not other- cytic lesion are absent, and the dermo- wise specified, seborrheic keratosis, acro- scopic features for a nonmelanocytic one chordon and basal cell carcinoma [4]. are observed, the lesion should be diag- The present case is a keratotic compound nosed as a nonmelanocytic pigmented le- nevus showing prominent epidermal fea- sion [2]. tures. This case demonstrates that a kera- The present case showed none of the crite- totic melanocytic nevus may be misdiag- ria for a melanocytic lesion. Histopathologi- nosed as a seborrheic keratosis both clini- cally the extensive keratotic plugs and horn cally and dermoscopically. pseudocysts which were seen as pseudofol- licular openings and milia-like cysts respec- References tively on dermoscopy may have obscured the nevus cell nests which were coinciden- 1. Soyer HP, Argenziano G, De Giorgi V, et al. Dermo- tally mostly right underneath them, thus scopy: A Tutorial. EDRA Medical Publishing & New leading to a diagnosis of a seborrheic kera- Media, Milan, 2000. tosis instead of a compound nevus. 2. Argenziano G, Soyer HP, Chimenti S, et al. Dermo- scopy of pigmented skin lesions: results of a con- Melanocytic nevi showing marked epidermal sensus meeting via the Internet. J Am Acad Derma- hyperplasia and hyperkeratosis seen fre- tol 2003; 48: 679–693. PMID: 12734496 quently together with horn pseudocysts 3. Gürbüz O, Hurwitz RM. Keratotic melanocytic ne- have been described as keratotic melano- vus. Int J Dermatol 1990; 29: 713-715. PMID: 2269566 cytic nevi [3, 4]. Histologically they are re- ported to consist 6% of melanocytic nevi. 4. Horenstein MG, Prieto VG, Burchette JL Jr, Shea CR. Keratotic melanocytic nevus: a clinicopa- They are commonly biopsied since many are thologic and immunohistochemical study. J Cutan clinically considered atypical besides having Pathol 2000; 27: 344-350. PMID: 10917161

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