Composite trichoblastoma and inverted follicular keratosis: a case report

Abstract

Composite trichoblastoma and inverted follicular keratosis is extremely rare and the histogenesis is unclear. To date, only four cases have been described in a report. We report a case of 62-year-old woman patient with a palpable cutaneous nodule on the buttock. The patient had a history of squamous cell carcinoma on the lower lip 13 months ago. Excisional biopsy was done, and the microscopic examination revealed composite tumor of trichoblastoma and inverted follicular keratosis. The patient has not been experienced recurrence after surgery.

Keywords: Composite tumor; inverted follicular keratosis; trichoblastoma.

Figure 1

(A) At low power, composite trichoblastoma (TB) and inverted follicular keratosis (IFK) are present, separately. Clefts (arrow) between the follicular stroma of TB and the normal dermis are identified. (B) At medium power, IFK is characterized by an epithelial cell proliferation with various stages of squamous differentiation and residual foci of basaloid cell (arrow). (C) Trichoblastoma has a nest of basaloid cells with peripheral palisading of nuclei, surrounded by follicular stroma. By immunohistochemistry, Bcl-2 was expressed in tumor cells of TB. (D) CD10 was negative in tumor cells (D), whereas it was positive in peritumoral stroma (E) of TB.