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September 2004

Clonal Seborrheic Keratosis: A Dermoscopic Pitfall

Arch Dermatol. 2004;140(9):1169. doi:10.1001/archderm.140.9.1169-b

We congratulate Hirata and coworkers1 for their report on the dermoscopic features of 2 cases of clonal seborrheic keratosis. We would like to add some comments based on our observation of a pigmented clonal seborrheic keratosis on the leg of a 72-year-old woman.

As in Hirata et al's cases, dermoscopic examination revealed large areas of a bluish pigmentation composed of multiple, variously sized and irregularly distributed, blue-gray roundish structures, also aggregated to form short lines (Figure 1). In our case, the blue-gray structures were similar to the so-called blue-gray ovoid nests, which are a dermoscopic hallmark of pigmented basal cell carcinoma.2,3 The clinical features and the additional dermoscopic observation of comedolike openings, few milialike cysts, and the jelly sign were all in favor of the diagnosis of seborrheic keratosis.3,4 However, the presence of blue-gray ovoid nests raised the need for a histopathologic examination, which revealed a clonal seborrheic keratosis. As reported by Hirata et al, the blue-gray ovoid nests corresponded histopathologically to multiple nests of pigmented basaloid cells within the epidermis (Figure 2).

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