JPC SYSTEMIC PATHOLOGY
SIGNALMENT (JPC Accession #2694985): Dog, age and breed unspecified
HISTOPATHOLOGIC DESCRIPTION: Salivary gland, submandibular: Affecting 50% of the normal section is a well-demarcated area of coagulative necrosis characterized by retention of tissue architecture with a loss of differential staining (infarct), admixed with multifocal areas of moderate hemorrhage, fibrin, edema, basophilic granular mineral, moderate numbers of neutrophils, and eosinophilic and karyorrhectic debris (lytic necrosis) which multifocally extends into the interlobular interstitium and adjacent capsule. The capsule is also multifocally, mildly thickened by granulation tissue characterized by increased numbers of reactive fibroblasts, fibrous connective tissue, edema, and small-caliber blood vessels. Ducts at the margin of the area of infarction are multifocally separated by fibrosis and are lined by degenerate epithelial cells with swollen, pale, vacuolated cytoplasm (degeneration) that occasionally pile up and fill the duct lumen (hyperplasia), or by multiple layers of flattened epithelium (squamous metaplasia) with lumens filled by a small amount of edema, secretory product and degenerate neutrophils.
MORPHOLOGIC DIAGNOSIS: Salivary gland, submandibular: Coagulative and lytic necrosis, acute, focally extensive, marked with ductular degeneration, hyperplasia and squamous metaplasia (infarct) breed unspecified, canine.
CONDITION: Salivary gland infarction or canine necrotizing sialometaplasia
- Rare, focally extensive to diffuse, ischemic necrosis of salivary adenomeres often secondary to infarction
- Reported in dogs, primarily small breed terriers, and cats
- Primarily involves the mandibular salivary gland, typically unilateral
- Dogs treated with sialectomy alone or nonsurgical methods have poor clinical outcomes often resulting in euthanasia; sometimes anticonvulsant medications help
- Unknown (possibly trauma, infection, or hypersensitivity etiology)
- Vascular compromise due to trauma has been suggested
- Positive staining for IgG and C3 within vessel walls in one case suggests the possibility of a type-III hypersensitivity reaction and an immune-mediated etiology
- In one reported case of systemic disease with Bartonella henselae and vinsonii subsp. berkhoffii infection, granulomatous inflammation, necrosis and ductal squamous metaplasia were noted in salivary glands
TYPICAL CLINICAL FINDINGS:
- Vomiting, anorexia, gagging, ptyalism, weight loss
- Submandibular swelling and pain
- +/- Leukocytosis with neutrophilia, monocytosis lymphopenia
TYPICAL GROSS FINDINGS:
- Glands may be enlarged, hard, and hemorrhagic
- Thickened capsule and dry cut surfaces
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Well-demarcated areas of coagulative necrosis of acinar cells
- Necrotic tissue is bordered by a band of congestion, hemorrhage, neutrophils, macrophages, and lymphocytes
- Ductal hyperplasia and squamous metaplasia; can be mistaken for neoplasia, stains strongly with cytokeratin confirming epithelial origin
- Vascular thrombosis
- Vessels in necrotic areas may have fibrinoid necrosis of the tunica media and thrombosis
- Variable degrees of fibroplasia
Grossly enlarged and hemorrhagic salivary gland:
- Salivary neoplasia (SCC, adenocarcinoma, carcinoma, adenomas)
- Note squamous metaplasia of ducts often easily mistaken for malignant transformation histologically
- Sialoadenitis (inflammatory cells, mucus/pus), sialocele/salivary mucocele (pseudocyst, not lined by epithelium; more common)
- Similar lesions have been reported in cats
- Histologically resembles a condition described in humans known as necrotizing sialometaplasia (NS), which generally resolves spontaneously
- Boydell P, Pike R, Crossley D, Whitbread T. Sialoadenitis in dogs. J Am Vet Med Assoc. 2000;216(6):872-874.
- Brooks D, Hottinger H, Dunstan R. Canine necrotizing sialometaplasia: a case report and review of the literature. J Am Anim Hosp Assoc. 1995;31:21-25.
- Brown PJ, Bradshaw JM, Sozmen M, Campbell RH. Feline necrotizing sialometaplasia: a report of two cases. J Feline Med Surg. 2004;6(4):279.
- Kelly D, Lucke V, Denny H, Lane J. Histology of salivary gland infarction in the dog. Vet Pathol. 1979;16:438-443.
- Kim HY, Woo GH, Bae YC, Park YH, Joo YS. Necrotizing sialometaplasia of the parotid gland in a dog. J Vet Diagn Invest. 2010;22(6):975-977.
- Saunders GK, Monroe WE. Systemic granulomatous disease and sialometaplasia in a dog with Bartonella Vet Pathol. 2006;43:391-392.
- Spangler W, Culbertson M. Salivary gland disease in dogs and cats: 245 cases (1985-1988). J Am Vet Med Assoc. 1991;198(3):465-469.
- Uzal FA, Platter BL, Hostetter JM. Alimentary System. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. 6th ed. St. Louis, MO: Elsevier; 2016: 30.