Carcinoma

Primary Liver Tumours

Hepatocytic

• more in dogs and cats

Gross

• can be difficult to distinguish grossly from adenomas
• usually one single large mass and additional smaller masses (intrahepatic metastases)
• may have features of malignancy such as internal necrosis and haemorrhage

Microscopically

• can be very variable appearing as sheets or cords of neoplastic cells
• cells generally smaller with a higher nucleus to cytoplasmic ratio

Cholangiocellular - bile duct

• more common than adenoma
• reported in all species (mostly dogs and cats)

Gross

• usually multiple whitish umbilicated nodules that are present diffusely throughout the liver
  • actually look as though they were secondary tumours
• firm on cut surface
  • due to fibrosis

Microscopically

• distinctly adenocarcinomatous
• ductal and acinar proliferation in abundant fibrous tissue
• sometimes papillary formations

Secondary Liver Tumours

• from a variety of origins

Pancreatic

Pancreatic carcinoma (Image sourced from Bristol Biomed Image Archive with permission)

Image of haemorrhage and pancreatic carcinoma in a cat from Cornell Veterinary Medicine

• In older dogs, more common in Airedale terriers, rare in cats, other species too
• Tend to arise centrally in the gland
• Highly invasive and infiltrative
• Metastases to the liver, visceral serosa, abdominal lymph nodes, spleen, adrenals etc.
• Similar to malignant ovarian tumours - implant on the peritoneum

Gross appearance

Pancreatic carcinoma (Image sourced from Bristol Biomed Image Archive with permission)

• Usually spherical nodules with adhesions to nearby structures
• Single or multiple, variable size
• Greyish or yellow fibrous tissue - firm on cutting
• May show internal necrosis and haemorrhage
• Some tumours may contain cysts wih mucinous content
• Adhesions may occur

Microscopic appearance

• May be well differentiated with normal acini and ducts
• Or diffuse sheet of undifferentiated cells

Endocrine Pancreatic

• Larger than adenomas
• Multilobular
• Invasive into parenchyma and surrounding tissue
• Metastasis into lymph nodes, liver mesentery, omentum
• Few mitotic figures

Peritoneal

• Carcinomas
  • Image of carcinoma in a cow's peritoneum from Cornell Veterinary Medicine
  • Must be differentiated from mesotheliomas
  • More common than sarcomas
  • Sometimes very scirrhous
  • May resemble chronic peritonitis when present with ascites
  • Absence of adhesions