Category:Liver - Proliferative Pathology

Especially in the dog, the liver is frequently affeced by both primary and secondary neoplasms.

Primary tumours

• not as common as secondary tumours
• may arise from each of the four main tissues within the liver
  • liver parenchymal cells
    • hepatoma
    • liver cell carcinoma
  • bile ducts
    • cholangioma
    • bile duct carcinoma
  • blood vessels
    • haemangioma
    • haemangiosarcoma
  • connective tissue
    • fibroma
    • sarcoma

NB: liver cell tumours and malignant bile duct tumours are the two most common primary hepatic neoplasms

Hepatocytic

• liver cell tumours are usually seen as discrete masses within the liver parenchyma
• the tumour tissue is usually reddish brown in colour
• can be malignant, metastases occuring tothe local lymph nodes and lungs

Adenoma

• seen mostly in sheep and cattle

Gross

• a single, pale, soft, often large nodule
• well demarcated from adjacent tissue, often with a noticeable capsule

Microscopically

• normal hepatocytic appearance
• no portal tracts within the mass
• a capsule surrounds the growth

Carcinoma

• 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

Adenoma

• very rare
• reported in dogs and cats

Carcinoma

• more common
• 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

Haemangiosarcoma

• can be primary in the liver
• other predilection sites
  • spleen
  • right auricle of the heart
• prevalent in large breeds

Secondary tumours

• Secondary metastatic involvement of the liver is very common
• in the dog, malignant pancreatic and splenic tumours commonly metastasise to the liver

Melanomas

• uveal melanoma in the cat

Lymphosarcoma

• the most common secondary malignancy
• can be present as nodules or be diffuse infiltration along the portal tracts

Gross

• enlarged liver
• turgid and friable
• many minute pale foci
• diffusely pale

Microscopically

• tumour cells are seen to spread diffusely through the sinusoids

Carcinomas

• from a variety of origins

Sarcomas

Mast cell tumours