JPC SYSTEMIC PATHOLOGY
Signalment (JPC # 2241434): Cocker spaniel
HISTORY: Tissue from a cocker spaniel with a long-standing history of otitis externa
HISTOPATHOLOGIC DESCRIPTION: Slide S-N06a: Glabrous skin, ear canal: Expanding the dermis, and elevating the overlying, hyperplastic epidermis, is an unencapsulated, well-circumscribed, moderately-cellular, polypoid neoplasm composed of cuboidal cells lining variably ectatic to cystic tubules, occasionally piling up to form multiple layers and papillary projections, supported by a moderate fibrovascular stroma. Neoplastic cells have indistinct cell borders, moderate amounts of eosinophilic granular cytoplasm, and round to oval nuclei with finely-stippled chromatin and one distinct nucleolus. Mitoses average 1 per 10 HPF. Diffusely, lumina of tubules are filled with pale homogeneous eosinophilic to gray-brown material (cerumen), few sloughed epithelial cells, macrophages, degenerate neutrophils and necrotic debris. Multifocally, there are few scattered lymphocytes, plasma cells, and macrophages that often contain intracytoplasmic brown material (cerumen). Diffusely, the epidermis is hyperplastic with acanthosis, occasional rete ridges and mild orthokeratotic hyperkeratosis. There is multifocal epidermal erosion and ulceration.
MORPHOLOGIC DIAGNOSIS: Glabrous skin, ear canal: Ceruminous gland adenoma, cocker spaniel, canine.
Signalment (JPC #1416286): Cat
HISTORY: Both ear canals contained variably sized nodules projecting from the pinna and occluding the canal. The nodules were white to dark blue and firm.
HISTOPATHOLOGIC DESCRIPTION: Slide S-N06b: Haired skin, ear canal: Expanding the dermis, focally distorting the auricular cartilage, and elevating the hyperplastic, ulcerated epidermis, is an unencapsulated, poorly-circumscribed, infiltrative, densely-cellular neoplasm composed of polygonal cells arranged in nests, tubules and acini with multifocal luminal papillary ingrowths supported by a moderate fibrovascular stroma. Neoplastic cells have variably distinct cell borders, moderate amounts of finely granular, eosinophilic, often vacuolated cytoplasm, and irregularly round to oval, occasionally vesiculate, nuclei with finely stippled chromatin and 1-2 magenta nucleoli. There is moderate anisokaryosis and anisocytosis. Mitoses average 2 per HPF. Focally within the subcutis, a vessel contains a nest of neoplastic cells surrounded by fibrin. The stroma contains multifocal aggregates of many lymphocytes, fewer plasma cells, neutrophils, and macrophages that are often laden with brown). material (cerumen Adjacent ceruminous glands are ectatic, lined by attenuated cuboidal cells and are variably filled with abundant brown to eosinophilic secretory product (cerumen), necrotic debris, sloughed epithelial cells, macrophages, degenerate neutrophils and occasionally acicular cholesterol clefts. Multifocally, sebaceous glands are mildly hyperplastic. Diffusely, the epidermis overlying the neoplasm is hyperplastic, with acanthosis and rete ridge formation. There is multifocal mild orthokeratotic hyperkeratosis and epidermal ulceration and erosion.
MORPHOLOGIC DIAGNOSIS: Haired skin, ear canal: Ceruminous gland carcinoma, breed unspecified, feline.
- 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
- Mixed or complex ceruminous gland tumors are morphologically similar to apocrine gland tumors
- Represents a continuum from benign to malignant
- May develop secondarily to recurrent bouts of otitis externa; inspissation of cerumen may play a role in development
- Adenocarcinomas are locally invasive, expansile and may metastasize to the regional lymph nodes, lungs and systemic viscera
TYPICAL CLINICAL FINDINGS:
- Head-shaking, scratching at the ear, hemorrhage from the ear canal
- +/- peripheral vestibular signs (head tilt, nystagmus), deafness, Horner's syndrome
TYPICAL GROSS FINDINGS:
- Smooth nodular or pedunculated, often exophytic, mass in the ear canal
- Difficult or impossible to distinguish from cystic dilation and epithelial hyperplasia (hyperplastic polypoid otitis externa), especially in cocker spaniels
- Smooth or ulcerated, soft or firm, and brown on cut section
- Adenomas: Usually <1 cm diameter, exophytic, only ulcerated if secondarily infected
- Carcinomas: Larger, more likely to be ulcerated; may invade the surrounding parotid salivery gland, soft tissues, or bone; may form a mass at the base of the ear
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Hallmark: intraluminal deeply-eosinophilic to brown/orange colloid-like material (cerumen); +/- small brown intracytoplasmic globules in neoplastic epithelium
- 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
- Gross appearance is indistinguishable from hyperplastic polypoid otitis externa; may resemble feline inflammatory polyps
- Carcinomas may be confused with salivary carcinoma when they invade the parotid salivary gland, or bone, and when very anaplastic
- Other neoplasms of the external ear: Squamous cell carcinoma (most important skin tumor affecting the ear), carcinoma of undetermined origin, histiocytoma (dog), basal cell tumor, chondroma, chondrosarcoma and rhabdomyomas (cat)
- A case report of a complex ceruminous gland adenocarcinoma in a brown-footed ferret and a Scottish wildcat hybrid (Felis silvestris)
- Horses: Sarcoids and dentigerous cysts may occur at the base of the ear
- Laboratory rats: Under certain conditions (especially after long-term administration of some carcinogens), Zymbal's glands (under the mucosa of the ear or in the subcutis ventral to the ear) can become the origin of sebaceous adenomas or carcinomas
- De Lorenzi D, Bonfanti U, Masserdotti C, et al. Fine-needle biopsy of external ear canal masses in the cat: cytologic results and histologic correlations in 27 cases. Vet Clin Pathol. 2005:34(2):100-5.
- Drew SJ, Perpinan D, et al. Concurrent transitional meningioma and ceruminous gland adenocarcinoma in a Scottish wildcat hybrid. J Comp Pathol. 2016; 154:253-257.
- Goldschmidt MH, Goldschmidt KH. Epithelial and melanocytic tumors of the skin. In: Meuten DJ, ed. Tumors in Domestic Animals. 5th ed. Iowa State Press: Ames, IA, 2017:115, 119-120.
- Moisan PG, Watson GL. Ceruminous gland tumors in dogs and cats: a review of 124 cases. J Am Anim Hosp Assoc. 1996:32(5)448-452.
- Njaa BL. Tumors of the ear. In: Meuten DJ, ed. Tumors in Domestic Animals. 5th ed. Iowa State Press: Ames, IA, 2017:935-936.
- Njaa BL. The ear. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO:Elsevier-Mosby; 2017:1249-1250.
- Wilcock BP, Njaa BL. Special senses. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 1. 6th ed. St. Louis, MO: Elsevier Limited; 2016:507-508.