A case of sebaceous naevus of the leg with secondarily developed trichoblastoma.

© 2010 The Authors. doi: 10.2340/00015555-0793 Journal Compilation © 2010 Acta Dermato-Venereologica. ISSN 0001-5555 Sir, Sebaceous naevi (organoid naevi) are hamartomatous proliferations that usually appear at birth or early in life, and are most commonly located on the scalp and face (1). They often present as round or oval lesions, and occasionally distribute in a linear pattern (2). Frequently, sebaceous naevi are complicated by the development of secondary tumours, such as syringocystadenoma papilliferum, trichoblastoma, and trichilemmoma. Except for systematized sebaceous naevi, sebaceous naevi on the legs are extremely rare, and only three cases have been reported so far (3–5). Therefore, it is difficult to make a diagnosis of sebaceous naevus when it occurs on the leg in a linear distribution that is rather characteristic of non-organoid (keratinocytic) epidermal naevi. We report here a case of sebaceous naevus on the leg complicated by trichoblastoma. Molecular investigations for FGFR3 and PIK3CA mutations, both of which have been identified in non-organoid epidermal naevi (6, 7), were performed.