JPC SYSTEMIC PATHOLOGY
Signalment (JPC #2028098): Age and breed unspecified dog.
HISTORY: Tissue from a mass adjacent to the ear canal.
HISTOPATHOLOGIC DESCRIPTION: Haired skin, pinna: The deep dermis is expanded by an unencapsulated, well-circumscribed, multilobular neoplasm composed of two populations of cells. The first population is composed of cuboidal to columnar cells forming varisized islands and well-differentiated tubules supported by a dense fibrovascular stroma that frequently blends into irregular islands of cartilage. Neoplastic cells have indistinct cell borders, a small to moderate amount of granular eosinophilic cytoplasm and prominent apical blebbing. Nuclei are oval, with finely stippled chromatin and 1-2 prominent nucleoli. Mitoses average 3 per 10 HPF. Within tubules, neoplastic cells frequently form micropapillary projections into tubule lumina. Tubules are often ectatic, and contain amorphous amphophilic to eosinophilic material (secretory product), necrotic debris and hemorrhage. Multifocally underlying the neoplastic epithelial cells, there is a second population of neoplastic myoepithelial cells arranged in thin streams, with indistinct cell borders, small amounts of fibrillar eosinophilic cytoplasm, elongate nuclei with finely stippled chromatin and indistinct nucleoli, and no observable mitotic figures. Neoplastic myoepithelial cells blend in with several varisized islands of cartilage with neoplastic cells in lacunae separated by abundant cartilaginous matrix. Throughout the neoplasm, there are multifocal areas of cellular and karyorrhectic debris (necrosis). Within the stroma, there are a few lymphocytes, plasma cells and macrophages, some containing intracytoplasmic hemosiderin. There is diffuse, moderate epithelial hyperplasia, acanthosis, rete ridge formation, and orthokeratotic hyperkeratosis. In the remaining sections, ceruminous glands are often ectatic, filled with amorphous amphophilic to eosinophilic secretory product, and surrounded by a few neutrophils, macrophages, lymphocytes, plasma cells and erythrocytes.
MORPHOLOGIC DIAGNOSIS: Haired skin, near ear canal (per contributor): Mixed ceruminous gland tumor, breed not specified, canine.
- Ceruminous glands are modified apocrine sweat glands within the external auditory meatus; glands are surrounded by myoepithelial cells
- The majority are malignant in cats while the majority are benign in dogs
- Ceruminous gland adenocarcinomas are the most common malignant neoplasm in the external acoustic meatus of both dogs and cats
- Usually occur in the older animal
- Represents a continuum from benign to malignant
- May develop secondarily to recurrent bouts of otitis extern
- Adenocarcinomas are locally invasive, expansile and may metastasize to the regional lymph nodes, and systemic viscera
TYPICAL CLINICAL FINDINGS:
- Head-shaking, scratching at the ear, hemorrhage from the ear canal
- Small, well circumscribed, dome-shaped mass
- Carcinomas may invade the parotid gland region, causing a bulging and draining mass in this area
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Adenomas: Proliferation of well-differentiated acini and ducts usually surrounded by a single layer of myoepithelial cells; ducts are often cystic, lined by papillary projections, and contain a deeply eosinophilic or orange secretory product; atypia and mitoses are infrequent; seldom exceed 1 cm
- Carcinomas: Not markedly different from adenomas but have less secretion, more cellular anaplasia, may show invasion into an abundant peripheral fibrous stroma or entry into blood vessels or lymphatics
- Mixed tumors: Infrequent; myoepithelial proliferation, bone or cartilage formation
ADDITIONAL DIAGNOSTIC TESTS:
- CK7 and CK14
- Chronic otitis externa with cystic dilatation with epithelial hyperplasia can resemble ceruminous gland tumors grossly and histologically
- Salivary carcinoma: Ceruminous gland adenocarcinoma may invade the parotid region, and therefore be a gross differential; when anaplastic, it is difficult to differentiate ceruminous gland carcinomas from anaplastic salivary adenocarcinoma
- In cats, nasopharyngeal polyps frequently ascend the external auditory meatus but are clearly different histologically
- Cat: Other common neoplasms of the ears in cats include squamous cell carcinoma, basal cell tumors, melanocytic neoplasms, hemangiosarcomas and inflammatory polyps
- Recently identified in the Scottish wildcat hybrid (Felis sylvestris)
- Complex ceruminous gland adenocarcinoma reported in a brown-footed ferret
- Rats: Zymbal's gland tumors are tumors of the modified sebaceous glands of the external ear canal
- Drew SJ, Perpiñán D, Baily J.Concurrent Transitional Meningioma and Ceruminous Gland Adenocarcinoma in a Scottish wildcat hybrid (Felis silvestris). J Comp Pathol. 2016;154(2-3):253-7.
- Njaa BL. The ear. In: McGavin MD, ed. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Mosby; 2016:1248-1249.
- Rudmann DG, White MR, Murphey JB. Complex ceruminous gland adenocarcinoma in a brown-footed ferret (Mustela putorius furo). Lab Anim Sci. 1994;44:637-638.
- Wilcock BP, Njaa BP. Special Senses. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals, 6th ed. Philadelphia, PA: Elsevier; 2015:507-508
- Wilcock B, Dubielzig RR, Render JA. World Health Organization, International Histological Classification of Tumors of Domestic Animals: Histological classification of ocular and otic tumors of domestic animals. Second series, Volume IX. Armed Forces Institute of Pathology in cooperation with the American Registry of Pathology and the World Health Organization Collaborating Center for Worldwide Reference on Comparative Oncology, Washington, DC; 2002:36.