Proliferating Pilar Tumor Workup

  • Author: Amor Khachemoune, MD, CWS; Chief Editor: William D James, MD   more...
 
Updated: Aug 16, 2011
 

Imaging Studies

Imaging studies are not usually indicated, but they may show a lobulated cystic mass, coarse calcification, or ringlike mineralization.

Because some subcutaneous tumors located in the midline of the body may have connections to the central nervous system (eg, scalp cavernous angioma, which may be part of the symptom complex known as sinus pericranii), imaging tumors in this location with CT or MRI prior to removal should be considered.

The best modality to determine bony invasion or erosion is CT scanning,[14] and proliferating pilar tumors are frequently found as incidental subcutaneous nodules on brain CT scans. They most frequently display isointensity on T1-weighted images and heterogeneous signal on T2-weighted images.[15] However, for deeper tissue invasion, MRI is best.

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Procedures

Performing an excisional biopsy is recommended. Send as much of the lesion as possible for pathologic evaluation. Ideally, the entire lesion should be excised and submitted at the time of the biopsy.

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Histologic Findings

The neoplasm is well circumscribed, with islands of squamous epithelium undergoing trichilemmal keratinization. Horn pearls or squamous eddies may be present, as may foci of calcification and glycogen-rich clear cells.

The epithelial cells lining the cyst lack intercellular bridges. The peripheral layers palisade, while the deeper layer cells are swollen.

Anti-CK 5/6 may also stain strongly positive in this neoplasm. This is a monoclonal antibody that recognizes high molecular weight keratin intermediate filaments.

An increase in staining of nucleolar organizer regions, an indicator of proliferation, has also been proposed as an adjunct to differentiate benign and malignant proliferating trichilemmal tumors.[16]

A series of histological slides follows:

Proliferating trichilemmal cystic neoplasm. Well-cProliferating trichilemmal cystic neoplasm. Well-circumscribed neoplasm with central cornified cells (2X). Courtesy of Steve A. McClain, MD. Proliferating trichilemmal cystic neoplasm (20X). Proliferating trichilemmal cystic neoplasm (20X). Courtesy of Steve A. McClain, MD. Proliferating trichilemmal cystic neoplasm (400X).Proliferating trichilemmal cystic neoplasm (400X). Note the pleomorphism of keratinocytes and mitotic figures. Courtesy of Steve A. McClain, MD.

Ye et al[7] proposed a stratification of proliferating pilar tumors (PPTs) into the following 3 groups:

  • Group 1 - Circumscribed silhouettes with "pushing" margins; modest nuclear atypia; and an absence of pathologic mitoses, necrosis, and invasion of nerves or vessels
  • Group 2 - Similar to group 1 but manifest as irregular, locally invasive silhouettes with involvement of the deep dermis and subcutis
  • Group 3 - Invasive growth patterns, marked nuclear atypia, pathologic mitotic forms, and geographic necrosis, with or without involvement of nerves or vascular structures.

Group 1 may be regarded as benign, group 2 as having the potential for locally aggressive growth, and group 3 as also having metastatic potential. The latter 2 categories might be equated with low and high grades of malignancy among PPTs of the skin. Occasionally, PPTs have been misdiagnosed at squamous cell carcinomas.[17]

Therefore, determining the malignant potential of a proliferating pilar tumor may be challenging and additional parameters are often needed. For instance, malignant proliferating pilar tumors are more likely to stain positive with p53 and Ki-67 relative to benign proliferating pilar tumors and trichilemmal cysts, and CD34 immunoreactivity may distinguish a malignant proliferating pilar tumor from a squamous cell carcinoma.[17]

The cyst cavity contains amorphous eosinophilic keratin. The content is commonly calcified.

The cyst may also have dedifferentiated parts, further emphasizing the need for careful analysis.[18]

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Contributor Information and Disclosures
Author

Amor Khachemoune, MD, CWS  Mohs Micrographic Surgery, Dermatopathology, 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, The School of Medicine at Stony Brook University Medical Center; Medical Director, Founder and Owner, McClain Laboratories LLC

Steve A McClain, MD is a member of the following medical societies: American Society for Clinical Pathology and College of American Pathologists

Disclosure: McClain Laboratories, LLC Ownership interest Management position

Maria Christina Kessides, MD, MS  Resident Physician, Department of Dermatology, State University of New York Downstate Medical Center

Disclosure: Nothing to disclose.

Rashid M Rashid, MD, PhD  Resident Physician, Department of Dermatology, University of Texas, Houston, MD Anderson Cancer Center, and Morzak Research Initiative

Rashid M Rashid, MD, PhD is a member of the following medical societies: American Academy of Dermatology, Council for Nail Disorders, Houston Dermatological Society, Texas Dermatological Society, and Texas Medical Association

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 Medical Center

Daniel Mark Siegel, MD, MS is a member of the following medical societies: American Academy of Dermatology, American College of Mohs Micrographic Surgery and Cutaneous Oncology, American College of Physician Executives, American Society for Dermatologic Surgery, American Society for MOHS Surgery, and International Society for Dermatologic Surgery

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.

Specialty Editor Board

R Stan Taylor, MD  The JB Howell Professor in Melanoma Education and Detection, Departments of Dermatology and Plastic Surgery, Director, Skin Surgery and Oncology Clinic, 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 Surgery, American Dermatological Association, American Medical Association, American Society for Dermatologic Surgery, Christian Medical & Dental Society, and Society for Investigative Dermatology

Disclosure: Nothing to disclose.

Richard P Vinson, MD  Assistant Clinical Professor, Department of Dermatology, Texas Tech University Health Sciences Center, Paul L Foster 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.

John G Albertini, MD  Consulting Staff, Dermatologic Surgery, The Skin Surgery Center; Program Director, ACGME Accredited Fellowship in Procedural Dermatology

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.

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, Vice-Chairman, Residency Program Director, Department of Dermatology, University of Pennsylvania School of Medicine

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

References

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  17. Chaichamnan K, Satayasoontorn K, Puttanupaab S, Attainsee A. Malignant proliferating trichilemmal tumors with CD34 expression. J Med Assoc Thai. Nov 2010;93 Suppl 6:S28-34. [Medline].

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Proliferating trichilemmal cystic neoplasm. Well-circumscribed neoplasm with central cornified cells (2X). Courtesy of Steve A. McClain, MD.
Proliferating trichilemmal cystic neoplasm (20X). Courtesy of Steve A. McClain, MD.
Proliferating trichilemmal cystic neoplasm (400X). Note the pleomorphism of keratinocytes and mitotic figures. Courtesy of Steve A. McClain, MD.
 
 
 
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