Composite tumors associating trichoblastoma and benign epidermal/follicular neoplasm: another proof of the follicular nature of inverted follicular keratosis

Abstract

Trichoblastomas (TBs) are benign follicular tumors that can present either as solitary nodule or as multiple facial papules. Only one case of sporadic TB in a composite tumor has been reported, arising in an apocrine poroma. We report the association of TB and benign epidermal/follicular neoplasm in six patients. Clinical data available were collected. Serial sections and immunohistochemical (IHC) analysis for CK17 and human papilloma virus (HPV) were performed on available materials. Five of the six patients were males. Mean age at diagnostic was 56 years. Lesions were localized on the face and scalp in four of six patients. The lesions associated with TB were inverted follicular keratosis (IFK) in three cases, seborrhoeic keratosis (SK) in two cases and IFK with verruca vulgaris pattern in one case. IHC for HPV was negative in the four cases tested. Staining for CK17 was always positive in TB. It was often positive in the associated neoplasm. TB can be associated with benign epidermal/follicular neoplasm in composite tumors. The association of TB and IFK with direct connection between the lesions is another argument in favor of the follicular origin of IFK. TB can be added to the spectrum of SK-associated tumors. Battistella M, Peltre B, Cribier B. Composite tumors associating trichoblastoma and benign epidermal/follicular neoplasm: another proof of the follicular nature of inverted follicular keratosis.