JPC SYSTEMIC PATHOLOGY
DIGESTIVE SYSTEM
September 2018
D-N03

SIGNALMENT (JPC 1930834):  Adult woodchuck (Marmota monax)

HISTORY:  None

HISTOPATHOLOGIC DESCRIPTION:  Liver:  Infiltrating and replacing approximately 70% of the normal hepatic architecture is an unencapsulated, multilobulated, densely cellular neoplasm composed of polygonal cells arranged in disorganized, 5 to 6-cell- layer-thick trabeculae and fewer acini on a moderate fibrovascular stroma.  Neoplastic cells have variably-distinct cell borders, abundant eosinophilic granular to vacuolated cytoplasm, round nuclei with finely stippled chromatin and one to two distinct magenta nucleoli.  Anisocytosis and anisokaryosis are moderate and there are low to moderate numbers of cytomegalic, multinucleated neoplastic cells with occasional bizarre nuclei.  The mitotic rate averages 1 per 10 HPF.  There are multifocal areas of lytic necrosis with loss of normal hepatic architecture and replacement by eosinophilic cellular and karyorrhectic debris, hemorrhage, fibrin and fibrosis.  Within the adjacent compressed hepatic parenchyma, portal areas are expanded by numerous  lymphocytes and plasma cells and fewer neutrophils that occasionally bridge portal areas and are admixed with increased small biliary duct profiles (ductal reaction), and fibrosis.  Frequently, the cytoplasm of adjacent hepatocytes is expanded by granular material, imparting a microvacuolated appearance (vacuolar degeneration, glycogen type).  Multifocally neoplastic cells contain discrete clear cytoplasmic vacuoles (vacuolar degeneration, lipid type). 

MORPHOLOGIC DIAGNOSES:

  1. Liver: Hepatocellular carcinoma, woodchuck (Marmota monax), rodent.
  2. Liver: Hepatitis, portal, lymphoplasmacytic and neutrophilic, chronic, diffuse, moderate, with biliary hyperplasia, bridging fibrosis, and hepatocellular degeneration and necrosis.

ETIOLOGY:  Woodchuck hepatitis virus (WHV)

ETIOLOGIC DIAGNOSIS:  Hepadnaviral hepatitis and hepatocellular carcinoma

GENERAL DISCUSSION:

PATHOGENESIS:

TYPICAL GROSS FINDINGS:

TYPICAL LIGHT MICROSCOPIC FINDINGS:

ULTRASTRUCTURE:  Woodchuck hepatitis virion (aka “Dane particle”) is 42-48 nm, spherical, double-layered, with an electron-dense, 27-30 nm, slightly hexagonal or icosahedral core (nucleocapsid) surrounded by a closely adhered outer capsid or surface envelope

ADDITIONAL DIAGNOSTIC TESTS:  

DIFFERENTIAL DIAGNOSIS:  

COMPARATIVE PATHOLOGY:

REFERENCES:

  1. Barthold SW, Griffey SM, Percy, DH. Pathology of Laboratory Rodents and Rabbits. 4th ed. Ames, Iowa: John Wiley & Sons; 2016:55-58,113-114.
  2. Charles JA, Cullen JM, van den Ingh TSGAM, Van Winkle T, Desmet VJ. Morphological classification of neoplastic disorders of the canine and feline liver. In: WSAVA Liver Standardization Group, ed. WSAVA Standards for Clinical and Histological Diagnosis of Canine and Feline Liver Diseases Philadelphia, PA: Saunders; 2006:117-124.
  3. Cullen JM. Tumors of the liver and gall bladder. In: Meuten DJ, ed. Tumors of Domestic Animals. 5th ed. Ames, IA: John Wiley & Sons; 2017:602-615.
  4. Cullen JM, Stalker MJ. Liver and biliary system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 2. 6th ed. St. Louis, MO: Elsevier; 2016:310,345-347.
  5. Wright TL, Eshar D, Carpenter JW, et al. Suspected Hepadnavirus Association with a Hepatocellular Carcinoma in a Black-Tailed Prairie Dog (Cynomys ludovicianus). J Comp Path. 2017;157:284-290.
  6. Zadronzy LM, Williams CV, Remick AK, Cullen JM. Spontaneous hepatocellular carcinoma in captive prosimians. Vet Pathol. 2010;47(2):306-311.


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