Trichoepithelioma, also known as multiple papular trichoepithelioma or epithelioma adenoid cysticum, is a benign tumor originating from hair follicles.

bubble_chart Pathological Changes

The histological structure of multiple and solitary hair follicle tumors is identical. Tumors located in the dermis are composed of numerous basaloid cell clusters, with the peripheral basaloid cells arranged in a palisade pattern and the central cells forming a reticular, sieve-like structure. The clusters are surrounded by a distinct fibrous stroma. The tumors contain multiple keratin cysts, which are filled with fully keratinized material. Calcifications may be present around the cysts, staining dark blue. If the keratin cysts rupture, a foreign body giant cell reaction may occur in the stroma.

bubble_chart Clinical Manifestations

It can be divided into two types: multiple and solitary.

1. Multiple type: More commonly inherited as an autosomal dominant trait, it is more frequently seen in females, with onset usually before the teenage years. The rash typically distributes symmetrically along the nasolabial folds and can also occur on the nose, forehead, eyelids, and upper lip. The lesions are hemispherical, translucent nodules, 2-5mm in diameter, with a smooth surface and firm texture, ranging in number from ten to several hundred. Small lesions may coalesce into larger nodules. Telangiectasia may sometimes be observed. The lesions can remain unchanged for several years without subjective symptoms.

2. Solitary type: Not related to heredity. The age of onset is usually around 20-30 years, commonly occurring on the face. The tumor is firm, skin-colored, and less than 2cm in diameter.

Single lesions can be surgically removed, while smaller lesions can be treated with electrocautery, cryotherapy, or laser therapy. However, there is a lack of treatment options for multiple lesions. Dermabrasion may be attempted, but it carries a risk of scarring.

bubble_chart Differentiation

The multiple type often presents in childhood, with rashes distributed along both sides of the nasolabial folds as hemispherical, transparent nodules, which are clinically characteristic. This disease should be differentiated clinically from flat warts, sebaceous adenomas, syringomas, and neurofibromas. The histological features of trichoblastic tumor diseases are similar to those of basal cell carcinoma and are almost indistinguishable. A definitive diagnosis can only be made by closely combining clinical findings.

The solitary type of trichoblastoma needs to be differentiated clinically from pigmented nevi, epidermal cysts, fibromas, and other adnexal tumors.