Trichoepithelioma

What is a trichoepithelioma?

Trichoepithelioma is a rare benign skin neoplasm that arises from hair follicles.

It is classified as a benign adnexal tumour and most commonly appears as either a solitary lesion or multiple nodules on the face. They do not cause ulceration or itching and are generally considered harmless. Multiple lesions are usually inherited.

Trichoepithelioma is similar to trichoblastoma in that both are hair follicle tumours. However, trichoepitheliomas are more superficial whereas trichoblastomas tend to arise from the deep dermis.

A solitary trichoepithelioma on the nose 

Multiple trichoepitheliomata — his mother and sister are similarly affected 

A solitary desmoplastic trichoepithelioma 

Multiple familial trichoepitheliomata in skin of colour 

Who gets a trichoepithelioma?

Due to an autosomal dominant inheritance pattern, both males and females acquire the gene for multiple trichoepitheliomata. However, females are more commonly affected due to higher gene expression.

Multiple trichoepitheliomata typically start to develop in early childhood or around puberty while solitary trichoepitheliomas often present in the second or third decades of life. Overall, trichoepitheliomata are most often diagnosed in adult women.

The prevalence is unknown. However, one dermatopathology lab in the United States reported 2.14–2.75 cases of trichoepithelioma per year.

Conditions associated with trichoepitheliomata include Brooke-Spiegler syndrome, characterised by multiple familial trichoepitheliomata, and familial cylindromatosis.

What causes a trichoepithelioma?

Trichoepithelioma is caused by the benign proliferation of epithelial-mesenchymal cells (basal cells) of hair follicles. There are three variants: solitary, multiple, and desmoplastic.

• Solitary nodules are the least common and usually spare the eyelids. They do not follow an inheritance pattern and occur due to a mutation in the PTCH tumour suppressor gene.
• Multiple nodular trichoepitheliomata are the most common type, and can occur as part of a systemic disease. For example, Brooke-Spiegler syndrome is caused by a mutation in the CYLD oncogene and present with hair follicle tumours and sweat gland tumors (trichoepitheliomas, spiradenomas and cylindromas).
• Desmoplastic trichoepitheliomata arise from cells lining the hair follicle. They usually present as a single lesion and most commonly affect the face. They are caused by a mutation in the 9p21 and 16q12-q13 chromosome.

What are the clinical features of a trichoepithelioma?

These tumours are small (usually 1 cm in diameter), firm, round, flesh-coloured papules typically seen on the face, particularly the upper lip, nasolabial folds, nose, eyelids, and forehead. They are sometimes also seen on the scalp, neck, upper torso, or elsewhere on the body, and can be pink-blue in colour with a symmetrical distribution.

The desmoplastic trichoepithelioma is a solitary ring-shaped lesion which can mimic the appearance of a basal cell carcinoma.

How do clinical features vary in differing types of skin?

Trichoepithelioma presents similarly in different types of skin.

What are the complications of a trichoepithelioma?

• Recurrence (rare)
• Basal cell carcinoma
• Psychosocial implications
• Surgical complications (scarring and hypopigmentation)

How is a trichoepithelioma diagnosed?

• Preliminary diagnosis is made based on patient history and clinical examination.
• Dermoscopy may be helpful. Typically, multiple white clods of variable diameter are seen.
• Definitive diagnosis is often only made by histopathology after biopsy or surgical excision.

What is the differential diagnosis for a trichoepithelioma?

• Basal cell carcinoma
• Cutaneous squamous cell carcinoma
• Microcystic adnexal carcinoma
• Intradermal naevus
• Trichoblastoma
• Trichofolliculoma
• Milia
• Syringoma
• Cylindroma

What is the treatment for a trichoepithelioma?

Treatment options include:

• Excision or shave biopsy / surgical removal
• Cryotherapy
• Dermabrasion
• Curettage
• Radiofrequency ablation
• Laser therapy.

How do you prevent a trichoepithelioma?

Currently unknown.

What is the outcome for a trichoepithelioma?

Most patients with trichoepithelioma have an excellent prognosis. After excision of solitary nodules, recurrence is very rare. However, as trichoepithelioma has a similar histology to basal cells, there is a small risk of malignant transformation into basal cell carcinoma.