RecuRRent pigmented tRichoblastoma on nevus sebaceous

Case report. A 24-year-old male patient reported he had undergone removal of a brownish lesion recently appeared on a congenital lesion of the scalp and noticed its recurrence one month after the removal. The dermatological examination showed a just raised, grossly rectangular, 2 x 1.5 cm yellow plaque, with grainy surface and irregular borders; in the middle of the plaque there was no hair but some isolated hairs were observed on its outskirts. Almost in the center of the plaque was present a 2 mm papule, with blue discoloration (Fig. 1), that under dermoscopic examination appeared covered by a whitish veil (Fig. 2). The histological examination (Fig. 3, 4) of the previously removed lesion showed islets of basaloid cells with a tendency to follicular differentiation surrounded by fibroblastic stroma, without the formation of clefts between tumor tissue and stroma, leading to the diagnosis of trichoblastoma. These findings led to diagnose recurrent pigmented trichoblastoma on nevus sebaceous and to program the removal of the recurrent papule.