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Dermatology > BENIGN NEOPLASMS
Trichilemmoma
Article Last Updated: Feb 12, 2007
AUTHOR AND EDITOR INFORMATION
Section 1 of 10  
Author: William P Baugh, MD, Consulting Staff, Full Spectrum Dermatology
William P Baugh is a member of the following medical societies: American Academy of Dermatology and Christian Medical & Dental Society
Coauthor(s):
Walter D Kucaba, DO, Private Family Practice, Simpsonville, South Carolina;
David Barnette, Jr, MD, Chief of Dermatopathology, Departments of Internal Medicine and Dermatology, Naval Medical Center at San Diego;
James Kerr, MD, Head, Department of Dermatology, Naval Medical Center at San Diego; Professor, Department of Medicine, Division of Dermatology, University of California at San Diego;
Cynthia L Chen, BA, Clinical Assistant, Full Spectrum Dermatology
Editors: David P Fivenson, MD, Director, Wound Care Service, Department of Dermatology, Henry Ford Health System; Richard P Vinson, MD, Assistant Clinical Professor, Department of Dermatology, Texas Tech University School of Medicine; Consulting Staff, Mountain View Dermatology, PA; Edward F Chan, MD, Clinical Assistant Professor, Department of Dermatology, University of Pennsylvania School of Medicine; Catherine Quirk, MD, Clinical Assistant Professor, Department of Dermatology, Brown University; Dirk M Elston, MD, Director, Department of Dermatology, Geisinger Medical Center
Author and Editor Disclosure
Synonyms and related keywords:
tricholemmoma, benign neoplasms of the follicular epithelium, Cowden syndrome, Cowden's syndrome, Cowden disease, Cowden's disease, multiple hamartomas, multiple hamartoma syndrome, nevus sebaceous of Jadassohn
Background
In 1962, Headington and French first described trichilemmoma as a benign neoplasm with differentiation toward pilosebaceous follicular epithelium. Subtle clinical and distinctive histologic features may characterize these superficial cutaneous tumors. Their significance resides in the association with Cowden disease and the need to differentiate trichilemmomas from other more aggressive cutaneous tumors. Clinically, trichilemmomas present as smooth, asymptomatic papules or verrucoid growths. They may occur as a solitary lesion or as multiple lesions, and they are usually found on the face (see Media File 1). These lesions often mimic a basal cell carcinoma or a wart. Trichilemmoma should be considered in the differential diagnosis of any indistinct facial papule. Differentiation from a basal cell carcinoma or a trichilemmal carcinoma is needed for appropriate patient management. Trichilemmomas are often reported in association with a nevus sebaceous of Jadassohn. When multiple trichilemmomas are present, Cowden disease (multiple hamartoma syndrome) should be suspected, especially if associated with oral fibromas, goiter, gastrointestinal polyposis, or a family history of breast cancer. The diagnosis of trichilemmoma is usually obtained by microscopic examination, revealing distinct histologic features.
Pathophysiology
The underlying cause of trichilemmomas is unknown. Most appear to represent a benign tumor with differentiation towards the follicular outer root sheath (trichilemma). Because of its histologic similarity to a wart, some researchers have investigated a viral etiology. In 1987, Johnson et al1 performed histologic and ultrastructural analyses of 10 hyperkeratotic lesions on the extremities and 2 keratotic lesions on the face in a patient with Cowden disease. They were unable to find evidence of a viral infection in the tissues examined. In 1990, Leonardi et al2 performed a study on 25 trichilemmomas revealing no evidence of human papillomavirus DNA in the lesions. Cowden syndrome is a rare autosomal dominant condition characterized by the formation of multiple types of hamartomas and neoplastic growths, which may be found throughout different body systems. Because of this, Cowden syndrome is also known as multiple hamartoma syndrome. This syndrome is thought to be due to PTEN mutation. This defect demonstrates incomplete genetic penetrance with variable expressivity. Loss of heterozygosity may lead to tumor formation. Patients with Cowden syndrome usually present at age 30-40 years. The syndrome is allelic to other PTEN-related syndromes such as Lhermitte-Duclos disease (dysplastic cerebellar gangliocytoma) and Bannayan-Riley-Ruvalcaba syndrome, which is characterized by genital lentigines and hamartomatous growths. Families or patients with overlapping features have been described.
Frequency
United States
Trichilemmomas are relatively common benign neoplasms of the follicular epithelium. Their true incidence is hard to determine and is probably underestimated. Approximately 40 cases per 100,000 consecutive skin biopsies may be found every year in any given dermatopathologic laboratory. Unlike isolated trichilemmomas, multiple trichilemmomas associated with Cowden disease are very rare.
International
The international frequency is unknown.
Mortality/Morbidity
Trichilemmomas are benign follicular epithelial neoplasms. They are associated with minimal morbidity and no mortality. These tumors usually need to be differentiated clinically from a wart or a basal cell carcinoma. The only morbidity associated with these tumors occurs if they are treated as a basal cell carcinoma before histologic confirmation is obtained.
Race
Trichilemmomas may occur in any race. However, they are most common in white female patients, but they have also been reported in Japanese and black patients. Desmoplastic trichilemmomas (a histologic subtype of trichilemmoma) predominantly occur in white men over a wide age range, and the highest frequency is in the fifth decade.
Sex
- The male-to-female ratio of trichilemmomas is 1:1.
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- Cowden disease has a female predominance, with a male-to-female ratio of 1:3.
Age
Trichilemmomas predominantly occur in patients aged 20-80 years. However, onset may occur as early as age 4 years, with a median age of onset at 40 years.
History
- Patients with trichilemmomas usually give a history of a slow-growing papule and/or plaque on the face. Such lesions may be solitary or multiple.
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- Patients often desire reassurance that they do not have a skin cancer and/or seek an evaluation for cosmetic removal of the lesions.
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- Trichilemmomas are usually asymptomatic.
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- If presenting in a nevus sebaceous of Jadassohn, a trichilemmoma may appear as a new growth within the lesion. No single feature allows the clinical diagnosis of a trichilemmoma, but rather this diagnosis is usually rendered histologically. However, if multiple lesions are present on the face, trichilemmomas associated with Cowden syndrome may be suspected. Once the diagnosis of trichilemmoma has been given, reevaluating the patient for clinical features of Cowden syndrome may be prudent.
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Physical
Patients with trichilemmomas usually present with either a single papule or multiple, small, flesh-colored papules that are 1-5 mm in diameter on the face or the neck. When these lesions grow in size, small plaques may be found, particularly in the nasolabial fold region. As trichilemmomas slowly enlarge, they often produce a hyperkeratotic surface suggestive of a verruca or a cutaneous horn. Besides the central part of the face, the ears, the forearms, the hands, or within a nevus sebaceous of Jadassohn are other typical sites that are examined for these cutaneous lesions.
- Multiple neoplasms affect a number of body systems. These neoplasms may be of ectodermal, mesodermal, and/or endodermal origin. Some consider the findings of multiple facial trichilemmomas around the mouth, the nose, and the ears to be pathognomonic for Cowden syndrome.
- Other clinical features of Cowden syndrome include such findings as the following:
- Adenoid facies
- Craniomegaly
- Mucosal papillomas
- Scrotal tongue
- Sclerotic fibromas
- Punctate palmoplantar keratoses
- Acral keratoses
- These lesions may also be associated with vitiligo, lipomas, xanthomas, hemangiomas, schwannomas, and neurofibromas.
- Of most concern is the high incidence of breast and thyroid carcinomas in these patients. Some women with Cowden syndrome may present with breast carcinoma in their early 20s. Because of the high incidence of breast cancer in these patients, some surgeons have advocated prophylactic mastectomy. Systemic neoplasms in Cowden syndrome include the following:
- Breast fibroadenomas
- Breast adenocarcinoma
- Gastrointestinal polyps
- Thyroid carcinoma
- If diagnosis of trichilemmoma is rendered, the patient should be completely examined for evidence of Cowden syndrome. Ten key physical features to look for in establishing the diagnosis of Cowden syndrome include the following:
- Adenoid facies with facial trichilemmomas
- Craniomegaly
- High arched palate
- Oral papillomas producing a cobblestone appearance on the lips and the mucosal surfaces
- Goiter or palpable thyroid nodules/tumors
- Gynecomastia in men
- Fibrocystic breast disease and/or palpable breast nodules or tumors in women
- Acral keratoses on the dorsum of the hands and the wrists
- Palmoplantar translucent punctate keratoses
- Sclerotic fibromas on the extremities
- In 1983, Salem and Steck3 proposed diagnostic criteria for Cowden syndrome. See Cowden Disease (Multiple Hamartoma Syndrome) for a more definitive discussion in this area. The key clinical features were broken down into major and minor criteria and family history, as follows:
- Major clinical criteria
- Cutaneous facial papules
- Oral mucosal papillomas
- Minor clinical criteria
- Acral keratoses
- Palmar plantar keratoses
- Family history of Cowden syndrome
- Patients with desmoplastic trichilemmomas usually present with lesions less than 1 cm in diameter found predominantly on the face, the neck, the scalp, and, sometimes, on the chest or the vulva. Several reports have described desmoplastic trichilemmomas occurring on the upper eyelid. They may be indurated, with a depressed central region and a raised, annular border. Desmoplastic trichilemmomas, although not associated with Cowden disease, have been described arising from a nevus sebaceous.
Causes
The cause of a trichilemmoma is unknown. Some researchers have postulated that a virus may induce these lesions because of morphologic and histologic features that they share with a wart. However, to date, no evidence of a viral etiology exists, and no known risk factors are associated with the development of a trichilemmoma.
Basal Cell Carcinoma
Bowen Disease
Cowden Disease (Multiple Hamartoma Syndrome)
Cutaneous Horn
Follicular Infundibulum Tumor
Folliculoma
Neurilemoma
Trichoepithelioma
Trichofolliculoma
Other Problems to be Considered
Clear cell acanthoma
Clear cell basal cell carcinoma
Cystic panfolliculoma
Hidroacanthoma simplex
Lab Studies
- If clinical evidence of Cowden syndrome is present, the following tests may be considered in establishing the diagnosis and in searching for potential malignancies:
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- Triiodothyronine and thyroxine serum levels
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- CBC count with differential
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- Electrocardiogram
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Imaging Studies
- No imaging studies are needed for the evaluation of a trichilemmoma. However, the following imaging studies may be of use when completing a workup for Cowden syndrome:
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- Mammography
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- Thyroid scan
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- Upper and lower GI imaging series
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- Chest radiography
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- Radiographs of the long bones, the pelvis, and the skull
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Procedures
- A skin biopsy is used to establish the diagnosis of a trichilemmoma. A shave biopsy is most commonly performed (see Histologic Findings below).
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Histologic Findings
The following are histologic features found in a trichilemmoma; these features assist in establishing the diagnosis:
- The epidermis usually reveals hyperkeratosis, mild acanthosis, and, occasionally, a cutaneous horn.
- A lobular or platelike epidermal growth projecting downward into the dermis
- Cells high in the epidermis may be vacuolated and contain coarse keratohyaline granules.
- Cells located toward the center of the lobular growth are often pale staining or have clear cytoplasm. These cells contain glycogen and are periodic acid-Schiff (PAS) positive but diastase labile.
- Cells at the periphery of the tumor are more basophilic and exhibit palisading.
- An eosinophilic hyaline basement membrane zone surrounds the tumor. This eosinophilic rim is PAS positive and diastase resistant.
- Foci of epidermal keratinization with formation of squamous eddies may be present.
- A desmoplastic variant demonstrates central sclerotic collagen breaking the center of the tumor into small irregular islands.
The histologic differential diagnosis includes a hidroacanthoma simplex, which usually demonstrates ductal differentiation. A clear, basal cell carcinoma should also be considered but excluded based on the presence of mucinous stroma, mitoses, and if it demonstrates peripheral palisading but lacks the eosinophilic hyaline cuticle. Other epithelial neoplasms, such as the tumor of the follicular infundibulum, may be considered in the differential diagnosis. Trichilemmal carcinoma may be considered but excluded based on its invasive growth pattern and many mitoses.
A desmoplastic trichilemmoma is considered a histologic variant of the trichilemmoma. It is a benign neoplasm of the hair follicle that is derived from the outer root sheath or infundibular epithelium. This tumor demonstrates a biphasic growth pattern having features of a lobulated tumor and cells that form narrow, irregular cords, which penetrate into the dermis. The stroma surrounding the tumor cords appears sclerotic. An inflammatory cell infiltrate is often seen surrounding the epithelial strands of the tumor. Because of these features, differentiating this tumor from an invasive squamous cell carcinoma or a sclerosing basal cell carcinoma is important. Note that desmoplastic trichilemmoma has not been associated with Cowden disease.
Medical Care
The best medical treatment of a tricholemmoma is to begin by establishing the correct diagnosis. Because these tumors are benign, no medical treatment is required. However, a few treatment options are available, ranging from simple surgical excision to carbon dioxide laser tissue ablation.
Surgical Care
A standard surgical approach to a patient with a trichilemmoma is to perform a shave biopsy. This procedure provides a tissue specimen for histologic examination and facilitates removal of the epithelial growth. If the shave biopsy is performed flush to the skin surface, it often produces an excellent cosmetic result. However, performing a shave biopsy does not eliminate the possibility of a recurrence. Of course, excision is an option but is less commonly performed because of the benign nature of this neoplasm and its common location on the face.
- Electrodesiccation may be used to remove a trichilemmoma. However, electrodesiccation followed by curettage is not indicated for this benign neoplasm. This procedure produces unnecessary and unsightly scarring.
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- One report describes successful treatment of desmoplastic trichilemmoma (a variant of trichilemmoma) with Mohs micrographic surgery.
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- Probably the most elegant procedure to date for removing a trichilemmoma is the use of a carbon dioxide laser for tissue ablation. Carbon dioxide laser has been used for removal of a wide range of epidermal and dermal growths or neoplasms.
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- Under local anesthesia, the hypertrophic and hyperkeratotic epithelium characteristic of a trichilemmoma may be rapidly and precisely vaporized.
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- The coagulated tissue subsequently may be wiped away. This process is repeated until the tissue is flush with the surrounding skin surface and/or the tumor has been destroyed.
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- The remaining tissue and thermal debris is allowed to heal and usually separates from the epidermis in 3-5 days after the procedure. Reepithelialization is usually complete within 4 weeks.
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- This procedure is particularly useful if multiple trichilemmomas are present (eg, Cowden syndrome).
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- The carbon dioxide laser has the following advantages: It allows for precise tissue ablation. Multiple lesions can be treated with ease. The procedure can be performed quickly. Morbidity is minimal. Patient recovery time is relatively short. Cosmetic results are usually excellent.
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Consultations
If the diagnosis of trichilemmoma is established and no other clinical features or family history of Cowden syndrome is found, then no further consultation is needed. However, if the medical provider finds evidence of Cowden syndrome, referral to a dermatologist is needed. Secondary referrals may then follow, including consultation by a gastroenterologist, an internist, an endocrinologist, and a surgeon, if needed.
Prognosis
- Trichilemmomas are benign follicular epithelial neoplasms. They are associated with minimal morbidity and no mortality.
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Patient Education
- Educate each patient with a trichilemmoma regarding the benign nature of this epithelial neoplasm. Further education regarding its association with Cowden disease may also be provided, particularly if other clinical evidence for Cowden disease exists.
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Medical/Legal Pitfalls
- Cowden disease must be considered in any patient with trichilemmomas. Desmoplastic trichilemmomas may be histologically misdiagnosed as carcinomas, resulting in unnecessary surgery.
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| Media file 1:
A patient with trichilemmoma papules on the face. |
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| Media file 4:
Low-power histologic view of a desmoplastic trichilemmoma. |
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| Media file 5:
High-power histologic view of a desmoplastic trichilemmoma. |
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| Media file 7:
Clinical image of the face of a patient with Cowden syndrome. |
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| Media file 8:
Clinical image of the oral mucosa of a patient with Cowden syndrome. |
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| Media file 9:
Clinical image of palmar keratoses in a patient with Cowden syndrome. |
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| Media file 10:
Clinical image of sclerotic fibroma in a patient with Cowden syndrome. |
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| Media file 11:
Clinical image of multiple trichilemmomas in a patient with Cowden syndrome. |
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Trichilemmoma excerpt Article Last Updated: Feb 12, 2007
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