eMedicine Specialties > Dermatology > Benign Neoplasms

Trichilemmoma

Author: William P Baugh, MD, Assistant Clinical Professor of Dermatology, University of California Irvine School of Medicine and Western School of Medicine; Medical Director, Full Spectrum Dermatology; Consulting Staff, Department of Dermatology, St Jude Medical Center
Coauthor(s): David Barnette, Jr, MD, Chief of Dermatopathology, Departments of Internal Medicine and Dermatology, Naval Medical Center at San Diego; James H Kerr, MD, Former Head (Retired), Department of Dermatology, Naval Medical Center at San Diego; Walter D Kucaba, DO, Private Family Practice, Simpsonville, South Carolina; Cynthia L Chen, Western University of Health Sciences College of Osteopathic Medicine of the Pacific
Contributor Information and Disclosures

Updated: Mar 13, 2009

Introduction

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.¹

When multiple trichilemmomas are present, Cowden disease (multiple hamartoma syndrome) should be suspected, especially if associated with oral fibromas, goiter, gastrointestinal polyposis, thyroid disease, 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, although because of its histologic similarity to a wart, some researchers have investigated a viral etiology. In 1987, Johnson et al² performed histologic and ultrastructural analyses of ten hyperkeratotic lesions on the extremities and two 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 al³ performed a study on 25 trichilemmomas revealing no evidence of human papillomavirus DNA in the lesions. Most trichilemmomas, therefore, appear to represent a benign tumor with differentiation towards the follicular outer root sheath (trichilemma).

Cowden syndrome, also known as multiple hamartoma 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. This syndrome is thought to be due to the PTEN mutation, a germline mutation in exon 8 of the phosphatase and tensin homolog deleted on chromosome 10.⁴ It is a point mutation of C to T at codon 1003 (CGA → TGA, arginine → stop codon). This defect demonstrates incomplete genetic penetrance with variable expressivity. Loss of heterozygosity may lead to tumor formation.⁵

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.^6,7

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; however, 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 30 years.⁵

Clinical

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.
• Patients often desire reassurance that they do not have a skin cancer and/or seek an evaluation for cosmetic removal of the lesions.
• Trichilemmomas are usually asymptomatic.
• 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.

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 Steck⁸ 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.^9,10 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.^1,11

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.

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