"Malignant Ear Canal Tumors" TUMOR TIDBITS, A BIWEEKLY EMAIL NEWSLETTER FROM GULF COAST VETERINARY ONCOLOGY Number 82; December 20, 2002. ======================================================================= THIS WEEK'S TUMOR TIDBIT: Malignant Ear Canal Tumors. ======================================================================= Happy Holidays from Gulf Coast Veterinary Oncology ======================================================================= OVERVIEW * Ceruminous gland adenocarcinoma of the ear is a primary malignant tumor of the external auditory meatus arising from coiled tubular apocrine sweat glands (i.e., ceruminous glands). * It may be invasive and capable of distant metastasis. CLINICAL HISTORY AND SIGNS * Rare but the most common malignant tumor of the ear canal in dogs and cats * No known sex predisposition but the cocker spaniel may be predisposed * Mean age--dogs, 8-10 years; cats, 10.5-13 years * Early appearance--pale pink, friable, ulcerative, bleeding, nodular mass(es) * Late appearance--large mass(es) filling the canal and invading through canal wall into surrounding structures * Local lymphadenomegaly is common * Vestibular signs in some animals CAUSES AND RISK FACTORS * Chronic inflammation may play a role in tumor development. DIFFERENTIAL DIAGNOSES * Nodular hyperplasia, pedunculated inflammatory polyps (cats), squamous cell carcinoma, basal cell tumor, papilloma, sebaceous gland tumor, and ceruminous gland adenoma. DIAGNOSTIC FINDINGS * Laboratory results are usually normal * Skull radiography to determine involvement of tympanic bulla * Thoracic radiography to evaluate for lung metastasis * CT scan useful before radiotherapy * Cytologic examination of large lymph nodes may reveal inflammation, rarely metastatic cells * Histopathologic characteristics include apocrine type differentiation from ceruminous glands and local invasion into stroma TREATMENT CONSIDERATIONS * Ear canal ablation and lateral bulla osteotomy preferred over lateral ear resection * Radiotherapy for large or incompletely excised masses * Possible surgical or radiation complications include permanent or transient Horner's syndrome * Chemotherapy is generally not considered; attempts at sustained tumor control using oral chemotherapy have been tried with limited success EXPECTED COURSE AND PROGNOSIS * Median survival after lateral ear resection, 10 months (33.3% have 1 year survival). * Median survival after ear ablation and lateral bulla osteotomy, 42 months (75% have 1 year survival). * Median survival after radiotherapy (no resection), 39.5 months (56% have 1 year survival). WHAT DO WE DO AT GULF COAST? * Aggressive surgical resection is the treatment of choice. * Radiotherapy following incomplete surgical resection OR surgical resection following radiotherapy is very successful for local control. * Metastatic disease is uncommon, therefore attempts at cure are possible. ======================================================================= We hope this info helps and don't hesitate to call us Gulf Coast Veterinary Oncology! Kevin A. Hahn, DVM, Phd, Diplomate ACVIM (Oncology), drhahn@gcvs.com Janet K. Carreras, VMD, Diplomate ACVIM (Oncology), drcarreras@gcvs.com Glen K. King, DVM, MS, Diplomate ACVR (Radiology & Radiation Therapy), drking@gcvs.com Gulf Coast Veterinary Diagnostic Imaging & Oncology 1111 West Loop South, Suite 150, Houston, TX 77027 P: 713.693.1166 F: 713.693.1167 W: http://www.gcvs.com