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
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
|
Sex |
N |
Percent |
|
Female |
733 |
17% (21%) |
|
Female Spayed |
1562 |
36% (33%) |
|
Male |
1090 |
25% (25%) |
|
Male Castrated |
949 |
22% (21%) |
|
( Normal Population %) |
|
|
|
Breeds at |
N |
Probability |
OR |
95% |
|
|
English Cocker Spaniel |
29 |
<0.0001 |
4.4 |
3.0 |
6.4 |
|
Cocker Spaniel |
632 |
<0.0001 |
3.9 |
3.5 |
4.2 |
|
Welsh Terrier |
7 |
0.0133 |
2.9 |
1.4 |
6.2 |
|
Husky |
158 |
<0.0001 |
2.6 |
2.2 |
3.1 |
|
Samoyed |
50 |
<0.0001 |
2.5 |
1.9 |
3.4 |
|
Cockapoo |
45 |
<0.0001 |
2.3 |
1.7 |
3.2 |
|
Cairn Terrier |
38 |
0.0003 |
1.9 |
1.4 |
2.6 |
|
West Highland White Terrier |
74 |
<0.0001 |
1.8 |
1.4 |
2.3 |
|
Miniature Poodle |
180 |
<0.0001 |
1.7 |
1.5 |
2.0 |
|
Toy Poodle |
28 |
0.0134 |
1.7 |
1.1 |
2.4 |
|
Dachshund |
88 |
0.0001 |
1.6 |
1.3 |
2.0 |
|
Brittany Spaniel |
33 |
0.0239 |
1.5 |
1.1 |
2.1 |
|
Shih Tzu |
87 |
0.0051 |
1.4 |
1.1 |
1.7 |
|
Standard Poodle |
69 |
0.0300 |
1.3 |
1.0 |
1.7 |
|
Labrador Retriever |
393 |
0.0101 |
1.1 |
1.0 |
1.3 |
|
Breeds at |
N |
Probability |
OR |
95% |
|
|
Golden Retriever |
226 |
<0.0001 |
0.71 |
0.62 |
0.81 |
|
English Springer Spaniel |
40 |
0.0002 |
0.58 |
0.42 |
0.79 |
|
Shetland Sheepdog |
35 |
<0.0001 |
0.41 |
0.30 |
0.58 |
|
Doberman |
47 |
<0.0001 |
0.38 |
0.29 |
0.51 |
|
Mastiff |
4 |
0.0409 |
0.38 |
0.14 |
1.01 |
|
Newfoundland |
3 |
0.0171 |
0.28 |
0.09 |
0.88 |
|
Pug |
5 |
0.0005 |
0.27 |
0.11 |
0.65 |
|
Boxer |
31 |
<0.0001 |
0.24 |
0.17 |
0.34 |
|
Weimeraner |
5 |
0.0001 |
0.24 |
0.10 |
0.57 |
|
Chow Chow |
4 |
0.0003 |
0.23 |
0.09 |
0.62 |
|
German Shepherd |
42 |
<0.0001 |
0.22 |
0.17 |
0.30 |
|
Greyhound |
3 |
0.0000 |
0.17 |
0.05 |
0.52 |
|
Rottweiler |
15 |
<0.0001 |
0.15 |
0.09 |
0.25 |
|
Saint Bernard |
1 |
0.0015 |
0.11 |
0.01 |
0.75 |
|
Rhodesian Ridgeback |
1 |
0.0004 |
0.09 |
0.01 |
0.62 |
|
Shar-Pei |
1 |
<0.0001 |
0.04 |
0.01 |
0.27 |
|
Sebaceous Adenoma & Ductal Adenoma Site |
Percent |
|
Head |
49.6% |
|
Forelimb |
12.1% |
|
Hindlimb |
11.0% |
|
Neck |
6.3% |
|
Multiple |
5.6% |
|
Thorax |
4.0% |
|
Back |
3.4% |
|
Abdomen |
3.2% |
|
Perineum |
2.5% |
|
Tail |
2.2% |
|
Scrotal |
0.1% |
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
|
Sex |
N |
Percent |
|
Female |
63 |
11% (21%) |
|
Female Spayed |
216 |
40% (33%) |
|
Male |
97 |
18% (25%) |
|
Male Castrated |
170 |
31% (21%) |
|
( Normal Population %) |
|
|
|
Breeds at |
N |
Probability |
OR |
95% Confidence |
|
|
Cocker Spaniel |
158 |
<0.0001 |
9.90 |
8.36 |
11.73 |
|
Samoyed |
8 |
0.00340 |
3.08 |
1.59 |
5.96 |
|
Husky |
19 |
0.00029 |
2.45 |
1.60 |
3.76 |
|
Scottish Terrier |
9 |
0.02810 |
2.22 |
1.19 |
4.16 |
|
Shih Tzu |
17 |
0.01920 |
1.84 |
1.14 |
2.99 |
|
Breeds at |
N |
Probability |
OR |
95% Confidence |
|
|
Golden Retriever |
13 |
<0.0001 |
0.33 |
0.20 |
0.55 |
|
English Springer Spaniel |
3 |
0.02340 |
0.30 |
0.10 |
0.92 |
|
Doberman Pinscher |
4 |
0.00090 |
0.28 |
0.12 |
0.67 |
|
German Shepherd |
6 |
<0.0001 |
0.26 |
0.12 |
0.55 |
|
Shetland Sheepdog |
1 |
0.00012 |
0.08 |
0.01 |
0.58 |
|
Rottweiler |
1 |
<0.0001 |
0.07 |
0.01 |
0.49 |
|
Boxer |
1 |
<0.0001 |
0.05 |
0.01 |
0.38 |
|
Site |
Percent |
|
Head |
54.1% |
|
Hindlimb |
11.8% |
|
Forelimb |
11.1% |
|
Neck |
8.2% |
|
Thorax |
5.1% |
|
Abdomen |
3.6% |
|
Multiple |
2.6% |
|
Perineum |
1.6% |
|
Tail |
1.0% |
|
Back |
1.0% |
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
|
Sex |
N |
Percent |
|
Female |
86 |
18% (21%) |
|
Female Spayed |
148 |
30% (33%) |
|
Male |
159 |
33% (25%) |
|
Male Castrated |
92 |
19% (21%) |
|
( Normal Population %) |
|
|
|
Breeds at |
N |
Probability |
OR |
95% |
|
|
Cocker Spaniel |
84 |
<0.0001 |
4.6 |
3.6 |
5.8 |
|
Husky |
28 |
<0.0001 |
4.2 |
2.9 |
6.1 |
|
Samoyed |
6 |
0.0280 |
2.7 |
1.2 |
6.0 |
|
Scottish Terrier |
9 |
0.0093 |
2.6 |
1.4 |
5.1 |
|
West Highland White Terrier |
9 |
0.0549 |
2.0 |
1.0 |
3.8 |
|
Miniature Poodle |
19 |
0.0559 |
1.6 |
1.0 |
2.5 |
|
Breeds at |
N |
Probability |
OR |
95% |
|
|
Labrador Retriever |
24 |
0.0117 |
0.6 |
0.4 |
0.9 |
|
Golden Retriever |
21 |
0.0133 |
0.6 |
0.4 |
0.9 |
|
Doberman Pinscher |
5 |
0.0171 |
0.4 |
0.2 |
0.9 |
|
Rottweiler |
3 |
0.0124 |
0.3 |
0.1 |
0.8 |
|
Boxer |
3 |
0.0009 |
0.2 |
0.1 |
0.7 |
|
Site |
Percent |
|
Head |
39.5% |
|
Hindlimb |
13.6% |
|
Forelimb |
12.3% |
|
Neck |
11.1% |
|
Thorax |
7.0% |
|
Abdomen |
5.2% |
|
Perineum |
4.3% |
|
Back |
3.9% |
|
Multiple |
1.8% |
|
Tail |
1.0% |
|
Scrotum |
0.3% |
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
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