What is sebaceous hyperplasia?
Sebaceous hyperplasia is a benign condition characterised by an overgrowth of the sebaceous glands. These are present in the skin and their function is to produce sebum, an oily substance that hydrates the skin and keeps it flexible.
Sebaceous hyperplasia presents as small, shiny bumps on the skin, usually yellowish or flesh-coloured. They are most commonly found on the face, especially the forehead and nose and are typically between 2 and 4 millimetres in diameter. In some instances, sebaceous hyperplasia can also occur on other parts of the body such as the chest, genitalia, and even the vulva [1, 2, 3, 4].
Sebaceous hyperplasia is usually harmless and painless, however can be treated for cosmetic reasons [5, 1]. If treatment is desired, there are several options available, including electrocauterisation (the bump is damaged by electrical current and allowed to heal), laser therapy, cryotherapy (freezing the lesion with liquid nitrogen), and the application of retinol, a form of vitamin A that can help reduce or prevent the sebaceous glands from clogging.
In complex cases, antiandrogen medication, which lowers testosterone levels can be used as a last-resort option, however this is indicated only for women. Non-medical options include using skin cleansers or applying a warm compress on the bumps to help dissolve the buildup [1].
What is basal cell carcinoma?
Basal cell carcinoma (BCC) is the most common type of skin cancer, accounting for 80-90% of all skin cancers [6]. This cancer results from a malignant transformation (a cell mutating and turning cancerous) of the cells in the basal (bottom) layer of the epidermis - the outer layer of the skin [7].
While the development of BCC is a result of multiple factors including genetics and the environment, exposure to ultraviolet radiation (UV), especially the short-wavelength UVB, is the principal causative agent. The radiation damages the DNA in the basal cells, leading to growth of damaged cells which then form a tumour.
BCC is most common in fair-skinned adults over 50 years of age, and is very prevalent in white populations, with a lifetime risk of 30% [8, 9].
Diagnosis, treatment and prognosis of BCC
BCC usually presents as a growth or a bump on the skin, with a shiny texture and skin-like or pink colour. Sometimes, the lesions can be pigmented (dark in colour), and therefore resemble melanoma, another type of skin cancer [7].
To diagnose BCC, physical examination by a dermatologist or a primary care provider is needed, as well as a skin biopsy. The skin biopsy is instrumental to confirming the diagnosis and characterising the tumour [10].
This is an in-office procedure done under local anaesthesia, where a small sample of the lesion and/or surrounding skin is taken. In some cases, imaging techniques including optical coherence tomography or confocal laser microscopy can be used to visualise the tumour and the surrounding anatomy (such as nerves or blood vessels) [11, 12].
The prognosis of BCC is very good, especially given the fact that the cancer does not usually metastasise (spread to other parts of the body).
The treatment focuses on a complete removal of the lesion. Mohs surgery is a common treatment approach. Here, skin and tissue around the lesion is examined under the microscope during the surgery, guiding the decision to remove more tissue. Alternatively, the cancer can be treated with cryotherapy or electrocautery. Topical chemotherapy (drugs applied to the skin) can also be used, as well as radiotherapy to the tumour site [6, 7].
In the rare case of the tumour metastasising, a combination of chemotherapy and targeted therapeutics is used. Commonly used targeted therapies are vismodegib and sonidegib [13].
Consequently, the prognosis for BCC is very good. Following removal, 95% of patients do not experience recurrence.
What is the difference between sebaceous hyperplasia and basal cell carcinoma?
Sebaceous hyperplasia and basal cell carcinoma are both skin conditions, but they have distinct characteristics and are caused by different cellular changes.
Sebaceous hyperplasia is a benign (non-cancerous) condition characterized by an overgrowth of sebaceous glands - the glands in the skin that produce oil to keep the skin healthy. It typically presents as small, shiny, and yellowish or flesh-colored bumps on the skin, especially on the face. These bumps are usually painless [1].
On the other hand, basal cell carcinoma (BCC) is a type of skin cancer that arises from the basal cells, which are found in the lower layer of the epidermis. BCC often presents as red or pink bumps that are much larger than those of sebaceous hyperplasia [1]. BCC is associated with exposure to sunlight, which damages the DNA in the basal cells causing them to form a tumour.
In terms of diagnosis, sebaceous hyperplasia and BCC can be distinguished through dermoscopic examination and immunohistochemical staining. Dermoscopic analysis of sebaceous hyperplasia often reveals yellowish structures, which are a key feature differentiating it from BCC [14]. Immunohistochemical staining of samples (samples are stained by various dyes that highlight presence of certain molecules such as proteins) can also help differentiate these conditions [15].