What is Trichilemmoma?
Trichilemmomas are harmless tumors that come from hair follicles, first identified by Headington and French in 1962. They belong to a group of rare, benign tumors that originate from different parts of the hair follicle. Specifically, trichilemmomas come from the outer root sheath of the hair follicle, which is the part of the hair strand that provides nutrients and allows the hair to grow. Some other growths come from this same part of the hair including the dilated pore of Winer, pilar sheath acanthoma, and pilar cyst, all of which show different aspects of hair follicle development.
Often, trichilemmomas show up as nonpainful, bumpy growths on the skin, usually on the face or neck. They may appear alone or in groups. Because they look similar to other skin conditions like common warts, verrucous papilloma, basal cell carcinoma, or squamous cell carcinoma, they can be easily misdiagnosed. However, if a patient has multiple trichilemmomas, doctors should check for links to genetic syndromes, especially one called Cowden syndrome. Trichilemmomas can also be found with other benign tumors such as nevus sebaceous and syringocystadenoma papilliferum.
When looked at under a microscope, trichilemmomas show lobules, or small rounded outgrowths, that extend from the skin’s surface. These are made up of pale-to-clear cells surrounded by a thick, tape-like structure known as the basement membrane. The cells align in a certain way, which is referred to as peripheral palisading. In addition, there may be an increase in skin cells at the top layer of the skin (hyperkeratosis) as well as irregular skin surface (papillomatosis). A different type of trichilemmoma may also be seen, which is characterized by cells that appear to invade the surrounding tissue along with a thick, hardened substance known as stroma.
What Causes Trichilemmoma?
The exact reason why trichilemmoma, a kind of skin tumor, develops is still unclear. Scientists have tried to find out if there could be a link with viruses, like the human papillomavirus (HPV). This is because trichilemmoma shares characteristics with a skin condition called verruca that we know is caused by HPV.
Despite these efforts, many studies didn’t find any traces of HPV within trichilemmoma. However, one study managed to find HPV DNA in trichilemmomas found in patients with a condition called Cowden syndrome. But due to mixed results, it remains unclear if a virus is the definite cause of trichilemmoma.
This highlights the need for more research to figure out what exactly causes trichilemmoma.
Risk Factors and Frequency for Trichilemmoma
Trichilemmomas are a rare condition and we don’t know exactly how common they are in the general population. This is partly because these lesions are often misdiagnosed, so the real number might be higher than we think. Trichilemmomas mainly affect adults between 30 and 80 years old – the average age is 59 – and they’re not common in kids. People of all races can get trichilemmomas, and they’re a little bit more common in males. If you have Cowden syndrome, you have a 10% to 35% chance of having multiple trichilemmomas.
- Trichilemmomas are rare and often misdiagnosed, so the true number of cases may be higher than we think.
- Mainly affects adults between 30 and 80 years old, with an average age of 59.
- It’s not common in children.
- People of all races can get trichilemmomas, and they’re a bit more common in men.
- 10% to 35% of people with Cowden syndrome could have multiple trichilemmomas.
Signs and Symptoms of Trichilemmoma
Trichilemmomas are a type of skin growth usually appearing as a single, small bump that can range from a pink to a tan color. They’re typically about 1 to 5 mm in size. Some can look like a type of skin cancer known as pigmented basal cell carcinoma. These growths are commonly found on the head and neck, but can also appear elsewhere, including on the eyelids. Doctors often need to differentiate trichilemmomas from other skin conditions like skin warts, basal cell carcinoma, squamous cell carcinoma, and harmless skin growths. In addition, trichilemmomas can be seen along with other benign tumors such as nevus sebaceous and syringocystadenoma papilliferum. These typically occur on the scalp, but can be found elsewhere too.
A rare variation of trichilemmoma is known as a desmoplastic trichilemmoma. First described in 1985, this type usually appears as a single, symptom-free bump or lump that can be either smooth or rough to touch. Occasionally, they can have an ulcer and appear similar to basal cell carcinoma. These bumps are usually between 5 and 7 mm in size and rarely grow beyond 10 mm. They’re often found on the lip or nose, but can be seen in other areas too. Desmoplastic trichilemmomas grow slowly and are often found in men aged 50 or older. In some cases, they can grow alongside basal cell carcinoma.
Testing for Trichilemmoma
Trichilemmomas are a type of benign skin condition that can look similar to some other benign tumors as well as more serious skin cancers. If you have only one of these, you may not require any other tests or treatments. However, if you have more than one, then your doctor might need to check for a condition called Cowden syndrome.
Cowden syndrome is a genetic condition that you inherit from one of your parents. It happens due to a change in a specific gene, called the PTEN gene. This gene normally helps stop tumors from growing, so if it’s not working properly, that can lead to lots of benign skin growths called hamartomas. Additionally, people with this syndrome have a higher than usual chance of developing certain types of cancers, including breast, thyroid, endometrial, kidney, colorectal carcinoma, and melanoma. Cowden syndrome can also cause other symptoms, such as multiple polyps in the intestines, a larger than average head size, curvature of the spine, or intellectual disabilities.
By the time they reach their 30s, nearly all people with Cowden syndrome show signs of the condition on their skin. Trichilemmomas are the most common type of skin growth, but Cowden syndrome can also cause other types of skin growths like sclerotic fibromas, acral keratoses, mucocutaneous papillomas, palmoplantar pits, penile hyperpigmentation, neuromas, and lipomas.
If your doctor suspects that you may have Cowden syndrome, they should quickly refer you to a genetic specialist for further testing. The specialist will check for changes in the PTEN gene. If you’re diagnosed with the syndrome, they will then put you on a screening program for various types of cancer according to the recommended guidelines from the National Comprehensive Cancer Network (NCCN). This includes a yearly full-body skin check.
There’s currently no cure for Cowden syndrome, but a recent study has shown promising results using a medication called sirolimus. This medication inhibits a chemical in your body called mTOR, which tends to be overactive in people with Cowden syndrome. Some people who took this medication saw improvements in their skin and gut symptoms, as well as improvements in their neurological function.
Treatment Options for Trichilemmoma
Trichilemmomas are harmless skin growths that usually don’t need treatment. But if they’re causing discomfort or you’re unhappy with how they look, they can be removed. This can be done with surgery or a treatment that uses a high-energy laser, known as carbon dioxide laser therapy. Other treatment options may include electrocautery (using electricity to heat tissues), cryosurgery (freezing the growth), or dermabrasion (a procedure to smooth the skin).
Likewise, oral and mouth skin growths related to a condition known as Cowden syndrome can be treated with removal or laser treatment. Topical retinoids and salicylic acid, usually applied as a cream or gel, can help treat these growths and other skin conditions.
For a specific type of growth known as a desmoplastic trichilemmoma that’s found on the face, Mohs micrographic surgery is a very effective treatment. This is a precise surgical method that minimizes damage to healthy skin while completely removing the growth. This is particularly important for these growths, as they may be associated with another type of skin tumor known as a basal cell carcinoma.
What else can Trichilemmoma be?
When a doctor finds trichilemmoma, a type of skin tumor, they often have to rule out other similar conditions. The main one that comes to mind is basal cell carcinoma. This is a type of skin cancer that can look very similar to trichilemmoma – they can both appear as little growths on the face. Under the microscope, they have similarities as well, like the cells’ appearance. However, trichilemmomas have some unique features that basal cell carcinomas don’t. Certain staining tests can help tell them apart. For instance, CD34 stain is positive in trichilemmoma but negative in basal cell carcinoma, and the reverse is true for a stain called BerEP4.
Squamous cell carcinoma, another skin cancer, can also look like trichilemmoma. However, squamous cell carcinoma typically displays more abnormal cells and increased cell multiplication when compared to trichilemmoma. Verruca vulgaris, which is another name for common warts, can be easily confused with trichilemmomas too. A sample under the microscope, however, shows features like thickening of the skin, increased skin growth, and enlarged blood vessels, which help to differentiate it from trichilemmoma.
Inverted follicular keratosis also presents as a single growth on the face and can resemble a trichilemmoma. Under the microscope, unique features such as squamous eddies (which are clusters of squamous cells), help differentiate it from trichilemmoma. Though it may display clear cell changes and certain kinds of cells, it does not show the distinct thickened basement membrane that trichilemmomas do.
Additionally, doctors consider other harmless skin growths as potential diagnoses such as:
- Trichoblastoma
- Trichoepithelioma
- Dilated pore of Winer
- Pilar sheath acanthoma
- Poroma
- Fibrofolliculoma
- Trichodiscoma
Inherited genetic conditions can also lead to multiple growths on the face, which might be mistaken for trichilemmomas. These include conditions like Brooke-Spiegler syndrome, Birt-Hogg-Dubé syndrome, familial multiple trichoepithelioma, tuberous sclerosis, and Muir-Torre syndrome.
What to expect with Trichilemmoma
Trichilemmomas are usually harmless tumors and if they appear as single lesions, the outlook is very good. Removing them surgically usually leads to a full recovery. However, when they are part of a condition called Cowden syndrome, the outlook depends on whether and how far related cancers have spread. Thankfully, many of the cancers linked to Cowden syndrome can be cured if identified early.
Possible Complications When Diagnosed with Trichilemmoma
Solo trichilemmomas or skin tumors don’t usually cause problems. But treatment methods like surgical removal, laser therapy, or medications can sometimes lead to side effects. These include risks of developing scars, infections, or changes in skin color.
The most significant worries associated with Cowden syndrome, a genetic disorder, predominantly involve an increased risk of cancer. That’s why it’s really important to carry out the right kinds of screenings or tests as per the NCCN guidelines. This helps catch and manage these risks in the best possible way.
- Treatment side effects:
- Scarring
- Infections
- Changes in skin color
- Risks associated with Cowden syndrome:
- Increased risk of cancer
Preventing Trichilemmoma
When patients have just one trichilemmoma (a benign, or non-cancerous skin growth), treatment isn’t often very effective because these growths are typically harmless. In most cases, they don’t affect your day-to-day life, aside from the way they look. However, if a patient finds they have many of these growths, it’s important that doctors make them aware of the potential link to a certain genetic syndrome. They should then be quickly referred to a team of specialists for further investigation.
Getting to a genetics specialist quickly is key, as the root cause of the growths can potentially change their life significantly. Therefore, patients need to be told about the harmless nature of these growths, and how to tell them apart from non-melanoma skin cancers, like basal cell carcinoma. This education is crucial for patients to understand their condition and its implications for their health and wellbeing.
