Pilosebaceous units consist of the hair follicle and sebaceous glands. They are specialized epidermal adnexal structures that are responsible for hair growth and keeping hair healthy.
The hair follicle is made up of the hair bulb in the lower portion of the hair follicle, and the hair shaft, which emerges from the hair follicle. Sebaceous glands are connected to hair follicles and produce sebum, an oily substance that keeps hair and skin moisturized.
Tumours arising from the hair follicle are part of a large and diverse group of neoplasms called skin adnexal tumours. Hair follicle tumours can be benign or malignant growths.
Most hair follicle tumours are benign and can be removed with local complete surgical excision. However, it is important to make a correct diagnosis of the excised tumour in case the patient is at risk of internal malignancy. Some specific hair follicle tumours are seen in syndromes associated with internal malignancies,e.g. trichilemmomas in Cowden disease. Also, many benign tumours have a malignant counterpart which, although rare, may be locally aggressive and have the potential to spread and metastasize.
To achieve accurate diagnosis of skin adnexal tumours pathological evaluation of skin samples should be supported with the following information:
Patient’s age and sex
Location(s) of the lesion
Rate of tumour growth
Lesion is solitary or multiple
Any associated inherited or systemic diseases.
Small or superficial biopsy of a lesion is not recommended as it may result in inaccurate diagnosis. Deep and peripheral surgical resection margins should be performed to assure complete excision. Patients with malignant tumours should be closely followed up for potential regional and distant metastasis.