Adenocarcinoma

Adenocarcinoma- histological (Courtesy of BioMed Image Archive)

• Adenocarcinoma is the most common gastric neoplasm in small animals.
  • This is a tumour of the mucosal epithelium.
• These are genreally found in the fundus (particularly along the lesser curvature), and in the pylorus.
• There are two main internal appearances of gastric adenocarcinoma, both of which show thickened, oedematous, pale and firm tissue:
  

  Adenocarcinoma- gross (Courtesy of BioMed Image Archive)
  1. A diffuse infiltration of gastric mucosa by neoplastic glandular epithelial cells.
     • Causes a diffuse rugal thickening.
  2. A more solitary lesion that is seen as a thick plaque-like lesion
     • Generally has a central erosion/ulceration of the tumour tissue.
       • Distinguishable from a peptic ulcer as the edges of the eroded area are raised and thickened (tumour tissue).
• The external appearance of an affected stomach can include thickening of the draining lymphoid vessels due to tumour infiltration ('cording of the lymphatics') and evidence of a scirrhous reaction to the carcinoma.
• Adenocarcinomas are locally aggressive and spread via the lymphatics to the lymph nodes, lung, liver and adrenal glands.

Tumours of the Perianal Area

Adenocarcinomas of the Glands of the Anal Sac (Apocrine Glands)

• Apocrine glands are the true anal glands- not to be confused with the anal sacs or the perianal glands.
• Much less common than intestinal adenocarcinoma.
• Commoner in bitches than dogs.
• Can be bilateral.
• Consequences:
  • May cause local problems.
  • May metastasise.
  • Often secrete a parahormone-like substance to cause paraneoplastic syndrome.
    • This can arise even when the primary tumour is very small.
    • Results in bone resorption and hypercalcaemia,
      • In turn can cause renal failure. which in turn can cause renal failure.