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

Ceruminous glands: These are modified apocrine glands found in the external ear canal that produce a brown waxy material. The glands consist of a secretory component surrounded by myoepithelial cells, and a duct which opens directly onto the epidermal surface of the external ear canal.

• Benign Ceruminous Tumors
• Malignant Ceruminous Tumors
• References

Benign Ceruminous Tumors

Ceruminous Adenoma

Definition—Ceruminous gland adenoma: A simple benign tumor with differentiation to ceruminous secretory epithelium.

Definition—Complex and mixed ceruminous gland adenoma: Complex (compound) ceruminous tumors have proliferation of glandular and myoepithelial cells. Mixed ceruminous tumors show a metaplastic change of the myoepithelium to cartilage or bone.

Epidemiology & Etiology

It has been suggested that chronic inflammation of the ear canal predisposes the animal to neoplasms.

Clinical Presentation/Physical Exam Findings

The presenting signs of ceruminous gland tumors are similar to those of chronic otitis externa, as the tumor, particularly adenomas, may occlude the external ear canal. The dog may therefore present with signs of

• head shaking
• pawing or scratching at the ear
• otorrhea
• intermittent hemorrhage
• an offensive odor from the ear

Otoscopic examination of the ear canal will identify any underlying tumor. Exophytic pedunculated masses (may be smooth or ulcerated, soft or firm) are most often adenomas.

Tumor Pathology

Gross Findings

• Exophytic masses may be smooth or ulcerated, soft or firm, and have a brown color on cut section
• Secondary infection and inflammation are common

Microscopic Findings

• The overlying squamous epidermis may be hyperplastic or ulcerated
• The tumor is subdivided into multiple small lobules by fine connective tissue trabeculae
• The lobules of tumor cells may show central aggregation of a green/brown material (cerumen) and neutrophils
• Tumor cells vary from cuboidal to tall columnar and have basally located nuclei
• The cytoplasm is eosinophilic and abundant
• Occasional tumors have acrosyringial involvement, seen as small foci of tumor cells within the overlying epidermis
• Acute and chronic inflammatory cells are often interspersed throughout the trabecular connective tissue
• In complex tumors there is in addition to the above microscopic changes proliferation of myoepithelial cells and in mixed tumors these show chondroid and/or osseous metaplasia

Clinical Behavior

Ceruminous gland adenomas that are pedunculated rarely recur because of the ease of adequate surgical excision. Non-pedunculated ceruminous gland adenomas may be more difficult to adequately excise, and, are thus, more likely to recur.

Malignant Ceruminous Tumors

Ceruminous Carcinoma

Definition—Ceruminous gland carcinoma: A simple malignant tumor with differentiation to ceruminous epithelium.

Definition—Complex and mixed ceruminous gland carcinoma: Complex (compound) ceruminous tumors have malignant proliferation of glandular cells and an accompanying proliferation of myoepithelial cells. Mixed ceruminous tumors show a metaplastic change of the myoepithelium to cartilage or bone.

Epidemiology & Etiology

It has been suggested that chronic inflammation of the ear canal predisposes the animal to neoplasms. These tumors are more common in the dog than are complex and mixed apocrine gland tumors.

Clinical Presentation/Physical Exam Findings

The changes noted on physical examination are as described for benign tumors above, but infiltrative, erosive and ulcerative growths are more likely to be carcinomas.

Tumor Pathology

Gross Findings

• Exophytic masses may be smooth or ulcerated, soft or firm, and have a brown color on cut section
• Infiltrative tumors often invade the surrounding soft tissue structures.

Microscopic Findings

This tumor shares many of the histopathologic features of the ceruminous gland adenoma. Differences include:

• The cells are round to polygonal
• Nuclei are larger and pleomorphic
• Nucleus is vesicular and contains a single very prominent nucleolus
• Mitoses are numerous, varying from 1 to 8 per high power field
• Occasional tumors evoke a host desmoplastic response
• There is often multifocal intraepidermal invasion of the ceruminous ducts by carcinoma cells

Clinical Behavior

Ceruminous gland carcinomas are infiltrative and destructive of the surrounding tissues, and may become metastatic to the parotid and mandibular 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
• 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.

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