What is Trichoblastoma and Trichoepithelioma?
Trichoblastoma (TB) and trichoepithelioma (TE) are non-cancerous tumors related to hair cell growth that occur most frequently on the face and scalp of adults. Trichoepithelioma was first identified by Brooke in 1892 as epithelioma adenoides cysticum. Over the years, Pinkus, Lever, and Montgomery further refined this description, pointing out that these tumors originate from very versatile cells related to hair growth.
Trichoblastoma was first defined by Headington in 1970 as a specific kind of hair-related tumor. Later, in 1993, Ackerman and his colleagues further clarified it to include all non-cancerous tumors originating from hair cells. While TE and TB are different, TE can be seen as a specific type of TB.
These tumors are usually harmless and do not spread to other parts of the body. However, they can change into a more aggressive type of cancer called trichoblastic carcinoma (TBC). This transformation happens due to the loss of a protein that usually prevents tumors (p53) and increased activity in certain signals that stimulate cells to multiply (PI3-AKT). Unlike TE and TB, TBC can spread more easily to surrounding tissues, return after removal, and potentially spread to other parts of the body.
Risk Factors and Frequency for Trichoblastoma and Trichoepithelioma
It’s not completely clear how often TE/TB or related genetic syndromes occur in the general population, but it’s understood that these cases are quite rare. Usually, these sporadic lesions appear in adults who are 40 or older. On the other hand, Brooke-Spiegler syndrome, which often comes with spiradenomas and cylindromas, tends to mainly affect young women. Specifically, for every 1 male, there are between 6 and 9.6 females with the syndrome. There’s also a variant of this condition, known as MFT, which is characterized by numerous TEs mainly found on the nasolabial folds and inner eyebrows.
Signs and Symptoms of Trichoblastoma and Trichoepithelioma
TE/TB, often similar to BCC, typically shows up as small skin-colored bumps or nodules that grow slowly. These bumps are usually about 0.2 to 1 cm in size and are typically found on the head, such as the face or scalp. However, they can also appear on the torso or limbs and can even possibly affect areas like the vulva. It’s not unusual to see these lesions appear without the presence of other skin growths like inverted follicular keratosis or syringocystadenoma papilliferum.
In rare cases, these bumps or TBs may show up in conditions like sebaceus nevus, a condition known as Jadassohn’s disease. In such scenarios, they may look like clear, warty growths with a raised center and pigmentation. On the other hand, DTE often looks like firm skin-colored bumps, patches, or nodules that are white to yellow in color and have a dip in the center, typically found on the face or cheeks.
Brooke-Spiegler syndrome is a condition marked by the presence of multiple nodules that look like BCC, usually seen on the head and neck. The nodules are usually about 0.5 to 3.0 cm big, and can sometimes cluster together on the scalp to form a “turban tumor.” You may notice them growing quickly or bleeding, which could indicate a progression to malignancy – this happens in about 5 to 10% of cases. MFT presents as several, small skin-colored bumps and nodules, which are typically smaller (5 to 10 mm) and mostly seen in the inner eyebrows and nasolabial folds (the wrinkles running from the sides of the nose to the corners of the mouth).
Testing for Trichoblastoma and Trichoepithelioma
To evaluate a patient for a condition known as trichoepithelioma/trichoblastoma (TE/TB), doctors will first conduct a thorough review of the patient’s medical history and perform a detailed physical exam. Given that this condition can appear very similar to basal cell carcinoma (another type of skin growth) and other skin tumors, a skin biopsy is crucial. A skin biopsy is a procedure where a small sample of skin is removed and examined under a microscope.
Because these conditions share many of the same histopathologic features (which are the microscopic changes seen in disease), an immunohistochemistry (IHC) examination might be necessary. IHC is a laboratory method that uses antibodies to check for certain antigens (proteins) in a sample of tissue. Using a tool known as a dermoscope to examine the skin might not provide further clarification, as these types of lesions have features like branching vessels and gray oval-like clusters that aren’t distinct to this condition.
If a patient has multiple or recurrent lesions, a genetic workup might be needed. This can involve examining particular regions of the patient’s DNA – specifically, chromosome 9q21 (for MFT) or the CYLD gene (for Brooke Spiegler syndrome). These conditions involve changes in these specific genetic areas.
Treatment Options for Trichoblastoma and Trichoepithelioma
When an individual has a single TE/TB – these are harmless skin growths – it can typically be removed through surgery. However, when multiple growths are present, particularly on the face (as can happen with certain genetic syndromes), things can become more complex. In such cases, a specialized type of skin cancer surgery known as Mohs surgery may be recommended, especially when the growths penetrate deeply into or below the skin.
Having multiple surgeries on the face can result in visible scarring and cause significant emotional distress. Additionally, in cases where the growths are associated with genetic syndromes, they can return after surgery, which means a person could end up needing a number of surgeries and treatments during their lifetime, along with the associated scarring.
Currently, there are no universal guidelines for treating multiple skin growths. Besides surgical removal, treatments such as electrosurgery, dermabrasion, cryotherapy, and radiation therapy are limited and can be invasive. Radiation therapy, in particular, has been associated with an increased risk of skin cancer. There are other potential risks including scarring, pain, bleeding, infection, and the re-occurrence of the growths with these treatment options.
Laser treatments, using tools such as carbon dioxide, erbium:YAG, and diode lasers, can often remove many growths effectively and safely without them coming back or causing significant cosmetic concerns. However, frequent treatments can sometimes result in heavy scarring, changes in skin color, and local inflammation (including swelling, redness, ulceration, and burning).
Other treatments might include medication such as sirolimus, imiquimod, tretinoin, vismodegib, aspirin, and adalimumab. However, further tests are needed to understand how these treatments can work in these situations, because our current knowledge about them is mostly based on individual stories and experiences rather than large-scale studies.
What else can Trichoblastoma and Trichoepithelioma be?
When trying to confirm a diagnosis of nodular BCC (basal cell carcinoma), doctors compare it to tumorous epidermis/trichoblastoma (TE/TB) amongst other conditions. The cells in this tumor type have elongated centers and a noticeable lining along the edges which may extend into the skin layer beneath. Other features such as major shrinking around the tumor, abnormal cells, significant cell growth, tumor death, or a gel-like inflammation in the tissue surrounding the tumor may be present. Unlike TE/TB, BCC typically occurs in areas of the skin exposed to sunlight – like the face, neck, or head.
In more complex cases, specific markers such as CK20, which is known to stain benign cells in hair germs, can separate TE/TB from BCC. When performing the test, this marker can be used alongside an androgen receptor (AR) test. A positive AR result (combined with a negative CK20 result) may hint at BCC. However, some cases of BCC may have a positive AR that is only found in specific areas or may not be present at all.
DTE (desmoplastic trichoepithelioma) is another condition that may look similar to a particular type of BCC (MBCC), other types of tumors (like syringoma, microcystic adnexal carcinoma), and even skin cancer that has spread from the breast. For a more precise diagnosis, doctors may perform an IHC staining, but this must be correlated with other observable signs and features. Unlike these other conditions, DTE usually has CK20-marked cells.
The most recent guidelines established by the World Health Organization in 2018 recognize multiple variants of TB. Using tests that identify markers such as CD34, BCL-2, CK20, and PHLDA1 can help differentiate TB from BCC. Common gene mutations typical of BCC’s are often not present in TB, especially syndromic variants.
Fibroepithelioma of Pinkus (FeP) may resemble TE/TB and is a rare variant of BCC. When studied under a microscope, doctors often see significant dermal fibrosis and tumor cells with porous strands. Features such as an apparent lining around the porosities and a shrinking stroma with tumor cells are common. Most of the time, FeP stains positive for CK20 (85% cases), AR (77% cases), and BCL-2.
Basaloid follicular hamartoma (BFH) is also a benign tumor type that might resemble BCC and TE/TB and rises from a mutation in a gene called PTCH, located on the 9q23 chromosome. This gene is a receptor for the sonic hedgehog pathway, and mutations may cause abnormal tumor cell growth and development. However, BFH stays limited to the skin’s exterior layer and typically centers around hair follicles. In early stages of the disease, chains of basaloid cells connected to pilosebaceous units can be seen. In long-standing cases, these tumor cells could totally replace them.
What to expect with Trichoblastoma and Trichoepithelioma
The future health outlook for individuals with single trichoepithelioma or trichoblastoma (TE/TB) —these are types of benign skin tumors— is typically excellent. However, for those with family genetic disorders, there’s a significantly higher chance of these tumors reappearing.
Since these tumors frequently occur on the face or neck, doctors need to carefully consider the time, cost, and health concerns associated with repeated treatments. These can range from minor procedures to invasive surgeries.
Possible Complications When Diagnosed with Trichoblastoma and Trichoepithelioma
TE/TB diseases are non-cancerous conditions, so removing them surgically usually provides a cure. There’s a very low chance that the disease will come back or spread to other parts of the body. Complications can arise from surgery, other invasive treatments, and laser procedures. You can find more details about these in the “Treatment/Management” section.
Common Outcomes and Complications:
- Surgical removal typically cures TE/TB diseases
- Very low chance of the disease recurring or spreading
- Possible complications from surgery
- Possible complications from other invasive treatments
- Possible complications from laser procedures
Preventing Trichoblastoma and Trichoepithelioma
When a person has only one tumor (solitary lesion), the treatment for TE/TB—which are benign, or non-cancerous, tumors—is usually pretty straightforward. But when a person has a genetic syndrome that runs in their family, causing multiple tumors, the treatment can be much more complex. This is because there can be a risk of the tumors coming back, or of them being in tricky locations like on the face.
Anyone who has multiple tumors, or who knows that these tumors run in their family, should let their doctor know, as they may need more genetic testing. It’s important to remember – and your doctor will reassure you of this – that TE/TB are benign, meaning they aren’t cancer, and are not the same as a type of skin cancer known as BCC.
