GENERAL CONSIDERATIONS

Biologic Behaviour

•rare with an overall incidence of 0.17%

•however, salivary gland neoplasia comprises 30% of all salivary gland pathology

•majority of salivary gland tumors are malignant and epithelial (84%) with ADC most common

•other salivary gland tumors include mucoepidermoid carcinoma, complex carcinoma, cystadenocarcinoma, acinic cell carcinoma, undifferentiated carcinoma, SCC, OSA, FSA, giant cell tumor, MCT, and LSA

•major (i.e., parotid, mandibular, sublingual, and zygomatic) and minor accessory salivary glands can involved

•metastasis to the regional lymph node in 39% and distant sites in 16% cats

•metastasis to the regional lymph node in 17% and distant sites in 8% dogs

•benign salivary gland tumors are rare (compared to humans) although benign lipomatous infiltration, calcinosis circumscripta, and adenoma have been reported

CLINICAL FEATURES

Signalment

•age: older (> 10-12 years)

•breed predisposition: Siamese cats and Spaniel breeds

•sex predisposition: males in cats with a male-to-female ratio of 2:1, but no sex predilection in dogs

Clinical Signs

•clinical signs are non-specific and include halitosis, dysphagia, and exophthalmos

•unilateral firm, painless swelling of the:

•upper neck with mandibular and sublingual salivary gland tumors

•ear base with parotid salivary gland tumors

•upper lip or maxilla with zygomatic salivary gland tumors

•mucous membrane of lip or sublingual area with accessory salivary gland tumors

•DDx: mucocele, abscess, salivary gland infarction, sialadenitis, LSA, or reactive lymphadenopathy

DIAGNOSIS

General Considerations

•FNA to differentiate non-neoplastic from neoplastic masses

•regional radiographs to identify periosteal reaction or displacement of adjacent structures

•incisional biopsy for definitive diagnosis

Clinical Staging

TREATMENT

Surgical Treatment

•surgery is recommended if possible but many lesions are extracapsular, invasive, and involve vital structures

•parotid gland resection is difficult due to poorly defined margins and facial nerve involvement

•complete extirpation of the ipsilateral neck can be performed with good functional outcome despite poor ability to blink and predisposition to KCS (treatment: tarsorrhaphy and eye drops)

•surgery and radiation therapy has been used to treat 3 cases with microscopic disease resulting in good local control and prolonged survival

•role of chemotherapy unknown

Prognosis

•MST 516 days in cats

•MST 550 days in dogs

•surgery and radiation therapy can provide permanent local control and long-term survival

•incomplete resection will result in local recurrence

•histologic grade is not prognostic for salivary gland ADC

•poor prognostic factors in cats: low mitotic index (≤ 10 v > 10)

•poor prognostic factors in dogs: stage III-IV disease v stage I-II disease