Head and neck tumors are relatively common in aging cats. Understanding the differential diagnoses in this anatomic area is crucial as the diagnostic and therapeutic approaches may vary. This lecture will discuss feline oral tumors, sinonasal tumors, iris melanoma, Hodgkin's-like lymphoma, salivary gland tumors, tumors of the ear canal, and skin tumors.

ORAL TUMORS

Squamous cell carcinoma (SCC) is the most common tumor (over 70%) of the feline oral cavity, followed by fibrosarcomas (10-20%) and other tumors (osteosarcoma, epulides, lymphoma, melanoma, etc.). The median age of cats with oral SCC is 12 years, though cats below one year of age and as old as 21 years have been reported. Feline oral SCC may as a mass in the mouth noted by the owner, or for halitosis, weight loss, dysphagia or increased salivation. Some cases of SCC may demonstrate a true mass effect while others may simply be erosive and/or erythematous, mimicking periodontal disease. Loose teeth in an older cat should be evaluated for the possibility of underlying bone lysis, possibly due to SCC.

Feline oral SCC is an extremely invasive and malignant tumor and, to date, therapies that are consistently beneficial for feline oral SCC have not been found. The recurrence rate when treated with surgery alone is very high with a median survival time under a few months. The exception to this is cats with very small oral SCC involving the rostral or lateral mandible that may be treated with rostral or segmental mandibulectomy, respectively. Even these cases can have recurrence despite "clean" margins on histopathology. The use of radiation therapy as a sole treatment modality provided median survival times of < 3-6 months. Few reports exist on the sole use of chemotherapy for feline oral SCC and, despite the occasional clinical response, it is generally felt to be of modest benefit for the feline inoperable oral SCC patient. In general cats with inoperable oral SCC have a guarded to poor prognosis, with median survival times of 1-3 months and palliative and supportive therapy (multimodal analgesic therapy, feeding tube) is often most beneficial. A recent study in the UK demonstrated that the palliative use of a NSAID provided better survival times than no treatment at all.

Fibrosarcoma (FSA) is the second most common oral tumor in cats (10-20%) and generally occurs in older cats (median 11 years) though younger and older cats have been reported. There is no known gender predisposition or oral cavity site predilection, though most feline oral FSA arise in the gingiva. Little clinical information is available on cats with oral FSA. Most cats with oral FSA will present in ways similar to cats with SCC, except that cats with FSA nearly hallways have a mass effect at the tumor site. The workup for oral FSA is identical to that discussed above for oral SCC. Deep incisional biopsies are also recommended for definitive diagnosis.

Feline oral FSA are very locally invasive and require wide surgical excision. Minimal or conservative surgical excision generally results in local recurrence. Unfortunately, even aggressive surgical resection of these tumors with histopathologically confirmed "clean" margins may still result in recurrence in 20-30% of cases owing to their invasiveness. Though poorly reported, the use of radiation therapy may be beneficial in cases with incomplete surgical resection (microscopic disease), or when used palliatively (3-6 large doses) on inoperable disease. Similarly, despite chemotherapy is occasionally used in cats with large oral FSA in an attempt to downstage (cytoreduction) the tumor prio to surgical resection, or in cats with high-grade oral FSA (higher risk of metastatic dissemination).