eMedicine Specialties > Dermatology > Benign Neoplasms

Proliferating Pilar Tumor

Author: Amor Khachemoune, MD, CWS, Clinical Instructor, Mohs Micrographic Surgery, Department of Dermatology, State University of New York Downstate Medical Center; Consulting Staff, Department of Dermatology, Veterans Affairs Medical Center of Brooklyn
Coauthor(s): Steve A McClain, MD, Clinical Associate Professor, Department of Pathology, State University of New York at Stony Brook; Medical Director, Founder and Owner, McClain Laboratories LLC; Daniel Mark Siegel, MD, MS, Director, Procedural Dermatology Fellowship Program, Clinical Professor of Dermatology, Department of Dermatology, State University of New York Downstate; Rashid M Rashid, MD, PhD, Resident, Department of Dermatology, MD Anderson Cancer Center, University of Texas; Kimberly Silvers, MD, PhD, Staff Physician, Section of Dermatology, Guthrie Clinic
Contributor Information and Disclosures

Updated: Mar 10, 2008

Introduction

Background

A proliferating pilar tumor (PPT) is a rare neoplasm arising from the isthmus region of the outer root sheath of the hair follicle. It was first described by Wilson-Jones1 as a proliferating epidermoid cyst in 1966. PPT was then distinguished from proliferating epidermoid cysts in 1995.2 It occurs most commonly on the scalp in women older than 50 years.3 Most tumors arise within a preexisting pilar cyst. Even though they usually are benign in nature, malignant transformation with local invasion and metastasis has been described.4,5,6  A tentative stratification of PPTs into groups as benign, low-grade malignancy, and high-grade malignancy has been introduced. They may be inherited in an autosomal-dominant mode, linked to chromosome 3. See Pilar Cyst for more information.

Pathophysiology

A PPT usually arises in the setting of single or multiple pilar cysts. An asymptomatic nodule is often present for months to years before a rapid increase occurs in the size of the lesion. This is thought to signal neoplastic transformation of the cyst, with progression into a PPT. The underlying stimulus for this transformation is not known, but it has been hypothesized to be secondary to trauma, irritation, or chronic inflammation. In a review of 76 cases of PPTs seen in consultation from 1989-2000, Ye et al7 proposed a distinction between benign and malignant variants. The authors also proposed histologic criteria that could predict behavior.

Frequency

United States

These tumors are rare. Only a few cases of malignant transformation have been reported.

Mortality/Morbidity

The lesions are usually painless. Exophytic growth with ulceration and foul-smelling discharge may occur. Some lesions may grow very large and cause pressure necrosis on underlying tissues, especially on the scalp. Local recurrence following excision and/or metastasis has been reported in rare instances in which malignancy has occurred.

Sex

These tumors occur more commonly in females than in males.

Age

PPTs are most common in older individuals aged 50-75 years, although they have been reported in individuals aged 20-30 years.

Clinical

History

  • Patients usually report a slowly or rapidly enlarging nodule.
  • Patients may give a history of recent trauma to the site.
  • The nodule may have been present for months to years without symptoms.

Physical

  • Lesions usually are single, firm-to-soft, painless nodules.
  • The size may range from 1-10 cm, although lesions as large as 25 cm have been reported.
  • Inflammation, ulceration, bleeding, and/or yellowish discharge may occur.
  • The most common (90%) location is the scalp.
  • Other reported sites include back, chest, axilla, groin, gluteal region,8 thigh, vulva,9 and face.

Causes

A spectrum of transformation is hypothesized, which begins with a benign pilar cyst, proceeding to a PPT, and then to a malignant PPT. The stimulus for changes in these lesions is currently unknown, although trauma, inflammation, and irritation may play roles.

More on Proliferating Pilar Tumor

Overview: Proliferating Pilar Tumor
Differential Diagnoses & Workup: Proliferating Pilar Tumor
Treatment & Medication: Proliferating Pilar Tumor
Follow-up: Proliferating Pilar Tumor
Multimedia: Proliferating Pilar Tumor
References
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References

  1. Wilson-Jones E. Proliferating epidermoid cysts. Arch Dermatol. 1966;94:11.

  2. Sau P, Graham JH, Helwig EB. Proliferating epithelial cysts. Clinicopathological analysis of 96 cases. J Cutan Pathol. Oct 1995;22(5):394-406. [Medline].

  3. López-Ríos F, Rodríguez-Peralto JL, Aguilar A, Hernández L, Gallego M. Proliferating trichilemmal cyst with focal invasion: report of a case and a review of the literature. Am J Dermatopathol. Apr 2000;22(2):183-7. [Medline].

  4. Mehregan AH, Lee KC. Malignant proliferating trichilemmal tumors--report of three cases. J Dermatol Surg Oncol. Dec 1987;13(12):1339-42. [Medline].

  5. Saida T, Oohara K, Hori Y, Tsuchiya S. Development of a malignant proliferating trichilemmal cyst in a patient with multiple trichilemmal cysts. Dermatologica. 1983;166(4):203-8. [Medline].

  6. Weiss J, Heine M, Grimmel M, Jung EG. Malignant proliferating trichilemmal cyst. J Am Acad Dermatol. May 1995;32(5 Pt 2):870-3. [Medline].

  7. Ye J, Nappi O, Swanson PE, Patterson JW, Wick MR. Proliferating pilar tumors: a clinicopathologic study of 76 cases with a proposal for definition of benign and malignant variants. Am J Clin Pathol. Oct 2004;122(4):566-74. [Medline].

  8. Karaca S, Kulac M, Dilek FH, Polat C, Yilmaz S. Giant proliferating trichilemmal tumor of the gluteal region. Dermatol Surg. Dec 2005;31(12):1734-6. [Medline].

  9. Avinoach I, Zirkin HJ, Glezerman M. Proliferating trichilemmal tumor of the vulva. Case report and review of the literature. Int J Gynecol Pathol. 1989;8(2):163-8. [Medline].

  10. Chang SJ, Sims J, Murtagh FR, McCaffrey JC, Messina JL. Proliferating trichilemmal cysts of the scalp on CT. AJNR Am J Neuroradiol. Mar 2006;27(3):712-4. [Medline].

  11. Shet T, Modi C. Nucleolar organizer regions (NORs) in simple and proliferating trichilemmal cysts (pilar cysts and pilar tumors). Indian J Pathol Microbiol. Oct 2004;47(4):469-73. [Medline].

  12. Nyquist GG, Mumm C, Grau R, Crowson AN, Shurman DL, Benedetto P, et al. Malignant proliferating pilar tumors arising in KID syndrome: a report of two patients. Am J Med Genet A. Apr 1 2007;143(7):734-41. [Medline].

  13. Amaral AL, Nascimento AG, Goellner JR. Proliferating pilar (trichilemmal) cyst. Report of two cases, one with carcinomatous transformation and one with distant metastases. Arch Pathol Lab Med. Oct 1984;108(10):808-10. [Medline].

  14. Batman PA, Evans HJ. Metastasising pilar tumour of scalp. J Clin Pathol. Jul 1986;39(7):757-60. [Medline].

  15. Folpe AL, Reisenauer AK, Mentzel T, Rütten A, Solomon AR. Proliferating trichilemmal tumors: clinicopathologic evaluation is a guide to biologic behavior. J Cutan Pathol. Sep 2003;30(8):492-8. [Medline].

  16. Janitz J, Wiedersberg H. Trichilemmal pilar tumors. Cancer. Apr 1 1980;45(7):1594-7. [Medline].

  17. Kanitakis J, Bourchany D, Faure M, Claudy A. Expression of the hair stem cell-specific keratin 15 in pilar tumors of the skin. Eur J Dermatol. Jul-Aug 1999;9(5):363-5. [Medline].

  18. Mann B, Salm R, Azzopardi JG. Pilar tumour: a distinctive type of trichilemmoma. Diagn Histopathol. Jul-Sep 1982;5(3):157-67. [Medline].

  19. Morgan RF, Dellon A, Hoopes JE. Pilar tumors. Plast Reconstr Surg. Apr 1979;63(4):520-4. [Medline].

  20. Plumb SJ, Argenyi ZB, Stone MS, De Young BR. Cytokeratin 5/6 immunostaining in cutaneous adnexal neoplasms and metastatic adenocarcinoma. Am J Dermatopathol. Dec 2004;26(6):447-51. [Medline].

  21. Poiares Baptista A, Garcia E Silva L, Born MC. Proliferating trichilemmal cyst. J Cutan Pathol. Jun 1983;10(3):178-87. [Medline].

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Further Reading

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Keywords

proliferating trichilemmal cyst, pilar cyst, proliferating trichilemmal tumor, isthmus-catagen cyst

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Contributor Information and Disclosures

Author

Amor Khachemoune, MD, CWS, Clinical Instructor, Mohs Micrographic Surgery, Department of Dermatology, State University of New York Downstate Medical Center; Consulting Staff, Department of Dermatology, Veterans Affairs Medical Center of Brooklyn
Amor Khachemoune, MD, CWS is a member of the following medical societies: American Academy of Dermatology, American Academy of Wound Management, American College of Mohs Micrographic Surgery and Cutaneous Oncology, American Medical Association, American Society for Dermatologic Surgery, and American Society for Laser Medicine and Surgery
Disclosure: Nothing to disclose.

Coauthor(s)

Steve A McClain, MD, Clinical Associate Professor, Department of Pathology, State University of New York at Stony Brook; Medical Director, Founder and Owner, McClain Laboratories LLC
Steve A McClain, MD is a member of the following medical societies: American Society of Clinical Pathologists and College of American Pathologists
Disclosure: Nothing to disclose.

Daniel Mark Siegel, MD, MS, Director, Procedural Dermatology Fellowship Program, Clinical Professor of Dermatology, Department of Dermatology, State University of New York Downstate
Daniel Mark Siegel, MD, MS is a member of the following medical societies: American Academy of Dermatology, American Academy of Facial Plastic and Reconstructive Surgery, American College of Mohs Micrographic Surgery and Cutaneous Oncology, American College of Physician Executives, American Society for Dermatologic Surgery, American Society for Laser Medicine and Surgery, American Society for MOHS Surgery, and International Society for Dermatologic Surgery
Disclosure: Nothing to disclose.

Rashid M Rashid, MD, PhD, Resident, Department of Dermatology, MD Anderson Cancer Center, University of Texas
Disclosure: Nothing to disclose.

Kimberly Silvers, MD, PhD, Staff Physician, Section of Dermatology, Guthrie Clinic
Kimberly Silvers, MD, PhD is a member of the following medical societies: American Academy of Dermatology and Phi Beta Kappa
Disclosure: Nothing to disclose.

Medical Editor

R Stan Taylor, MD, Professor of Dermatology, University of Texas Southwestern Medical School; Director of Skin Surgery and Oncology Clinic, Department of Dermatology, University of Texas Southwestern Medical Center
R Stan Taylor, MD is a member of the following medical societies: American Academy of Dermatology, American College of Mohs Micrographic Surgery and Cutaneous Oncology, American Medical Association, American Society for Dermatologic Surgery, Christian Medical & Dental Society, and Society for Investigative Dermatology
Disclosure: Nothing to disclose.

Pharmacy Editor

Richard P Vinson, MD, Assistant Clinical Professor, Department of Dermatology, Texas Tech University School of Medicine; Consulting Staff, Mountain View Dermatology, PA
Richard P Vinson, MD is a member of the following medical societies: American Academy of Dermatology, Association of Military Dermatologists, Texas Dermatological Society, and Texas Medical Association
Disclosure: Nothing to disclose.

Managing Editor

John G Albertini, MD, Consulting Staff, Dermatologic Surgery, The Skin Surgery Center
John G Albertini, MD is a member of the following medical societies: American Academy of Dermatology and American College of Mohs Micrographic Surgery and Cutaneous Oncology
Disclosure: Nothing to disclose.

CME Editor

Glen H Crawford, MD, Assistant Clinical Professor, Department of Dermatology, University of Pennsylvania School of Medicine; Chief, Division of Dermatology, The Pennsylvania Hospital
Glen H Crawford, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American Medical Association, Phi Beta Kappa, and Society of USAF Flight Surgeons
Disclosure: Nothing to disclose.

Chief Editor

William D James, MD, Paul R Gross Professor of Dermatology, University of Pennsylvania School of Medicine; Vice-Chair, Program Director, Department of Dermatology, University of Pennsylvania Health System
William D James, MD is a member of the following medical societies: American Academy of Dermatology and Society for Investigative Dermatology
Disclosure: elsevier Royalty Other; american college of physicians Honoraria Other

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