Veterinary Society of
Surgical Oncology

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

SALIVARY GLAND TUMORS

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

T2-3

T1-3

N

N0

N0

N1

M

M0

M0

M0

IV

T1-3

N0-1

M1

Salivary Gland

Cat

Dog

Mandibular

59%

30%

Parotid

19%

50%

Sublingual and Minor Salivary Glands

6%

12%

Zygomatic

3%

4%

Undetermined Salivary Glands

13%

4%

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