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Meibomian Tumors

Supported by the Savannah and Barry French Poodle Memorial Fund
University of Pennsylvania School of Veterinary Medicine
Ultima Vez Modificado: 21 de agosto del 2005

Michael H. Goldschmidt, MSc, BVMS, MRCVS, Diplomate ACVP Professor and Head, Laboratory of Pathology and Toxicology Chief, Surgical Pathology Department of Pathobiology
Frances S. Shofer, PhD, Adjunct Associate Professor of Epidemiology and Biostatistics

Introduction

Meibomian glands are also known as tarsal glands. They are modified sebaceous glands which are located on the inner surface of the eye. These holocrine glands have a duct which opens at the eyelid margin.

The histologic classification of Meibomian tumors includes the following:

• Meibomian adenoma: a benign tumor arising from the meibomian (tarsal) glands located on the inner aspect of the eyelid

• Meibomian ductal adenoma: a benign tumor arising from the meibomian glands with a preponderance of ducts, and few sebocytes and basaloid cells

• Meibomian epithelioma: a tumor of low-grade malignancy arising from the meibomian glands with a preponderance of basaloid cells, and few sebocytes and ducts

• Meibomian carcinoma: a malignant tumor of meibomian glands

The vast majority of Meibomian gland tumors are benign. Carcinomas are uncommon. Only information of Meibomian adenomas will be discussed below.

Meibomian Adenoma

Epidemiology

Clinical Presentation/Physical Exam Findings

• Adenomas can be exophytic (protruding outward) or endophytic (extending into the eyelid)
• If found above the level of the surrounding mucosa, the tumor may ulcerate and cause keratoconjunctivitis (inflammation of the cornea and conjunctiva)
• Endophytic lesion may be seen on physical exam as a bulging mass beneath the mucosa and epidermis
• Often, such tumors are extremely pigmented (black) which may make it nearly impossible to differentiate from a melanocytoma

Tumor Pathology

Gross Findings

• Tumors often extend into the eyelid tissue, but remain well encapsulated
• In a cross section, they appear to range from black to dark grey to white
• Surrounding the tumor may be a zone of brownish discoloration, a focus of granulomatous inflammation, caused by the release of secretory products into this area

Microscopic Findings

• The overlying epidermis is often hyperplastic and may be papillomatous
• Discrete lobules are formed, which vary in size
• Variable numbers of basaloid reserve cells and sebocytes are present
• Basaloid reserve cells at the periphery of the lobules are from one to several layers in thickness
• Sebocytes predominate within the tumor
• Small or larger ducts, often lined by a brightly eosinophilic corrugated squamous epithelium, are often present
• A severe granulomatous response with multinucleated giant cells occurs when there has been rupture of the tumor and release of sebaceous secretion into surrounding stroma
• Tendency to be highly melanized, so must be differentiated from melanocytomas arising from this site

Clinical Behavior

Meibomian adenomas, ductal adenomas and epitheliomas are normally slow growing and easily recognized because of their location. Wide surgical excision may be curative, but recurrence may occur due to incomplete excision.

Meibomian carcinoma

Microscopic Findings

• Cells exhibit a variable degree of cytoplasmic lipidization
• Considerable nuclear and cellular pleomorphism are present
• Considerable mitotic activity
• Nuclear hyperchromasia

Meibomian gland carcinomas are very rare. When they do occur, they are locally destructive and may metastasize via the lymphatics to regional lymph nodes.

References

• Goldschmidt, M.H., & Hendrick, M.J. (2002). Tumors of the skin and soft tissue. In D.J. Meuten (Ed.), Tumors in domestic animals 4 th ed (pp. 45-119). Iowa: Iowa State Press
• Goldschmidt, M.H., & Shofer, F.S. (1998). Skin tumors of the dog and cat. Woburn, MA: Butterworth-Heinemann
• Gross, T.L., Ihrke, P.J., & Walder, E.J. (1992). Veterinary dermatopathology: A macroscopic and microscopic evaluation of canine and feline skin disease. (pp. 327-485). St. Louis, Missouri: Mosby Year Book
• World Health Organization (1998). Histological classification of epithelial and melanocytic tumors of the skin of domestic animals (2 nd series, vol 3). Washington, DC: Armed Forces Institute of Pathology
• Yager, J.A. & Wilcock, B.P. (1994). Color atlas and text of surgical pathology of the dog and cat. Ontario, Canada: Mosby Year Book.