Pigmented trichoblastoma arising from the nevus sebaceous: a rare case in Korea

Abstract

Trichoblastoma is occasionally observed in association with a pre-existing nevus sebaceous in the Korean literature. However, there has been no report on the pigmented type. Herein, we report the first Korean case of a pigmented trichoblastoma arising from the nevus sebaceous on the forehead. A 28-year-old male presented with a dark nodular lesion within a yellowish plaque on the forehead. The surrounding yellowish plaque on the forehead had existed since birth. The central, dark-pigmented nodule began to appear three years ago and enlarged gradually. Histopathologic findings of central pigmented lesion showed heavy melanin deposits within and around the tumor nests. Complete excision was made as treatment.

Keywords: Nevus sebaceous; Pigmented trichoblastoma.

Fig. 1

A distinct, dark, pigmented nodule developed on the yellowish, verrucous plaque.

Fig. 2

(A) Low power view showing nodular pigmented tumor nests involving the dermis. Heavy melanin deposits were noted within and around the tumor nests (H&E, ×40). (B) High power view revealed palisading basaloid tumor cells that lack high-grade cytologic atypia and fibrocellular stroma without clefting around the basaloid island (H&E, ×400).

Fig. 3

(A) Tumor cells do not stain with bcl-2 (×400). (B) Stromal cells around the tumor nests were weakly positive for CD10 (×400).