+ Biologic Behavior

  • 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


+ 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


+ 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


+ 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


T0 No evidence of neoplasia
T1 Tumor < 2 cm in diameter - Primary Tumor
T2 Tumor 2-4 cm in diameter
T3 Tumor > 4 cm in diameter
N0 No evidence of lymph node involvement
N1 Regional lymph node involvement - Node
M0 No evidence of metastasis
M1 Evidence of distant metastasis with site specified - Metastasis

Clinical Stage

I II III T T1 T2 T3 N N0 N0 N0 M M0 M0 M0 IV T1-3 N1 M0 V T1-3 N0-1 M1

Salivary Gland Mandibular Parotid Sublingual and Minor Salivary Glands Zygomatic Undetermined Salivary Glands
Cat 59% 19% 6% 3% 13%
Dog 30% 50% 12% 4% 4%