Cancer Types   /   OncoLink Vet

Sebaceous Gland Tumors

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Supported by the Savannah and Barry French Poodle Memorial Fund
University of Pennsylvania School of Veterinary Medicine
Last Modified: August 21, 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

The sebaceous gland, located within the dermis produces an oily material (sebum) that empties into the infundibulum of the hair follicle. A duct, lined by a squamous epithelium, is present between the gland and the hair follicle.

• Sebaceous Adenoma & Ductal Adenoma
• Sebaceous Epithelioma
• Sebaceous Carcinoma
• References

Sebaceous Adenoma

Definition: A benign tumor characterized by a preponderance of sebocytes (cells with intracytoplasmic lipid vacuoles) with few basaloid cells and ducts.

Sebaceous Ductal Adenoma

Definition (SDA): A benign tumor characterized by a preponderance of ducts, and fewer sebocytes and basaloid cells.

Epidemiology

Clinical Presentation/Physical Exam Findings

• These tumors grow both outward and inward.
• Those that protrude outward have a broad base of attachment to the skin and may become ulcerated.
• Those growths that grow inward extend into the dermis and deeper tissues and have well defined borders.
• The epidermis covering the tumor is usually hairless, may be hyperplastic and hyperpigmented, but usually smooth.
• The tumors range in size from 0.5 cm to 10 cm in diameter.

Tumor Pathology

Gross Findings

• Cut cross-section shows varying color schemes depending on the degree of sebaceous differentiation.
• Colors can vary from a gray-white to a yellow-white.
• Tumors are usually subdivided into lobules by fine trabeculae composed of connective tissue.
• They can extend into the subcutis and the borders are easily identified.
• Ulcerations are frequently associated with secondary bacterial infections.

Microscopic Findings

Sebaceous adenoma

• well demarcated intradermal mass
• may extend from the dermo-epidermal interface to the subcutis, replacing the normal tissue
• forms discrete lobules, which vary in size
• may have remnants of dermal collagen within the tumor
• variable numbers of basaloid reserve cells and sebocytes
• 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

Microscopic Findings

Sebaceous ductal adenoma

• extensive ductal differentiation
• ducts are haphazardly arranged and interspersed with basaloid reserve cells and lesser numbers of mature sebocytes 

Clinical Behavior

Recurrence is rare with adequate excision. Some dogs may develop additional tumors, especially on the head (but these are not metastatic lesions).

Sebaceous Epithelioma

Definition: A tumor of low-grade malignancy characterized by a preponderance of basaloid cells with few sebocytes and ducts.

Epidemiology

Clinical Presentation/Physical Exam Findings

• These masses are usually solitary, firm, nodular or plaque-like tumors.
• They range in size from several millimeters to several centimeters in diameter.

Tumor Pathology

Microscopic Findings

Histopathology

• preponderance of basaloid reserve cells 
• sebocytes may only be seen as individual cells within the tumor mass or as small aggregates
• basaloid cells may show marked mitotic activity
• little nuclear atypia 
• foci of ductal differentiation are found as small horn cysts 
• lymphatic invasion may occasionally be found at the periphery of a sebaceous epithelioma

Clinical Behavior

They tumors can be locally aggressive and may invade the lymphatics that surround the mass(es), and possible regional lymph nodes. This feature is most frequently encountered in Cocker Spaniels where the tumor is present on the head.

Sebaceous Carcinoma

Definition: A rare malignant tumor characterized by cells with a variable degree of sebaceous differentiation.

Epidemiology

Clinical Presentation/Physical Exam Findings

• This is an uncommon tumor that presents as a solitary red intradermal nodule.
• They are usually less than 4cm in diameter.
• The overlying skin does not have any hair.
• There is invasion of the subcutaneous tissue.

Tumor Pathology

Gross Findings

• These intradermal masses are difficult to differentiate from other intradermal carcinomas on gross evaluation.

Microscopic Findings

Histopathology

• consists of multiple lobules of tumor cells