JPC SYSTEMIC PATHOLOGY
REPRODUCTIVE SYSTEM
January 2019
R-B04

Signalment (JPC #1210466):  Cow

HISTORY:  None

HISTOPATHOLGIC DESCRIPTION:  Mammary gland (lactation stage):  Filling and replacing approximately 40% of ducts (both intralobular and interlobular) and extending into secretory units and the surrounding interstitium are numerous multifocal to coalescing areas of necrosis which are admixed with neutrophilic inflammation and contain numerous large (up to 25 um) colonies of 1-2um basophilic cocci.  Multifocally surrounding the necrotic foci are bands of fibrous connective tissue (fibrosis), moderate numbers of lymphocytes and plasma cells and rare macrophages.  Epithelial cells lining affected ducts, and occasionally within adjacent glands are attenuated, degenerate or necrotic (characterized by shrunken, hypereosinophilic cytoplasm and nuclear pyknosis).  Multifocally, remaining glandular lumina and intralobular ducts contain either eosinophilic homogenous material (secretory product), small amounts of necrotic cellular debris admixed with occasional macrophages, eosinophilic fibrillar material (fibrin), or basophilic, concentrically-lamellated foci up to 120 um in diameter (corpora amylacea).  Multifocally degenerate epithelial cells contain moderate amounts of brown granular pigment (hemosiderin).  Remaining glandular tissue is characterized by well-developed secretory alveoli, increased numbers and size of ducts, and decreased amounts of connective tissue (active lactating gland). Diffusely the interstitium is expanded by congested vessels and ectatic lymphatics (edema). 

Slide B:  Mammary gland (Brown and Brenn stain):  There are multiple large colonies of gram-positive cocci in the necrotic foci.

MORPHOLOGIC DIAGNOSIS:  Mammary gland:  Mastitis, necrosuppurative, subacute, multifocal to coalescing, severe, with large colonies of Gram-positive cocci, breed unspecified, bovine.

ETIOLOGIC DIAGNOSIS:  Staphylococcal mastitis

CAUSE:  Staphylococcus aureus

GENERAL DISCUSSION:

PATHOGENESIS:

VIRULENCE FACTORS for S. aureus:

TYPICAL CLINICAL FINDINGS:

TYPICAL GROSS FINDINGS:

TYPICAL LIGHT MICROSCOPIC FINDINGS:

ADDITIONAL DIAGNOSTIC TESTS:

DIFFERENTIAL DIAGNOSIS (GROSS & HISTO):  

Causes of mastitis in cattle:

COMPARATIVE PATHOLOGY:

Sheep/goats:  Similar to cattle

Dogs & cats:  Uncommon; early lactation; enter via fissures in nipples secondary to trauma

Pigs:

Horses:  Rare

South American Camelids:  Rare

Rabbits:  

Guinea pigs:  

Rats:  

Hamster: 

REFERENCES:

  1. Barthold SW, Griffey SM, Percy DH. Pathology of Laboratory Rodents and Rabbits. 4th ed. Ames, IA: John Wiley & Sons, Inc; 2016: 142-144, 186, 231, 284-286.
  2. Foster RA. Female reproductive system and mammae. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Elsevier; 2017:1183-1188.
  3. Ruegg PL, Erskine RJ, Morin DE. Mammary gland health. In: Smith BP,ed.  Large Animal Internal Medicine.  5th ed.  Louis, MO: Mosby Elsevier; 2015:1015-1043.
  4. Schlafer DH, Foster RA. Female genital system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. 6th ed. vol. 3. Philadelphia, PA:Saunders Elsevier;  2016:452-457.


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Click on image for diagnostic series.



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