• Common tumor type arising from glandular epithelial tissue.
• Prognosis: depends on site.
• Treatment: variable response to chemotherapy, surgery and/or radiation therapy which are the mainstays of treatment.
• In general malignant tumors/adenocarcinomas are much more common than benign adenomas/adenomas.
• Adenocarcinomas occur in the skin (sweat gland and ceruminous gland), oropharynx, nasal chamber, salivary gland, stomach, intestine, bile duct, gall bladder, mammary gland, larynx, trachea and lung.
• Adenomas occur in the skin (sweat gland), oropharynx, intestine, bile duct, mammary gland, kidney and thyroid gland.
• Adenocarcinomas are locally invasive and depending on site metastasize to local and distant sites
• Adenomas are non-invasive and do not metastasize.

Presenting signs

• Depends on site.
• Adenocarcinomas are often locally invasive and may be ulcerated.
• Adenomas are small, well defined and non-ulcerated.
• Sweat gland adenocarcinomas often occur on head and neck.
• Ceruminous gland adenocarcinoma in external and middle ear canal.
• In the gastrointestinal tract adenomas are rare, adenocarcinomas common, majority occur in small intestine (ileum or jejunum), causing diarrhea and/or vomiting, rarely in the stomach.
• Bile duct adenomas and adenocarcinomas occur with similar frequency and present with cranial abdominal mass/hepatomegaly and signs of vague malaise Liver: primary hepatic neoplasia and jaundice.
• Mammary adenocarcinomas often originate from the caudal two mammary glands. The mass may be ulcerated. There may be signs of tumor metastasis, eg dyspnea due to pulmonary metastasis.
• Nasal adenocarcinomas   →   nasal discharge, obstruction, sneezing.
• Oropharyngeal adenocarcinoma   →   dysphagia, salivation.

Age predisposition

• Generally older cats.

Breed/Species predisposition

• Siamese - small intestine adenocarcinoma.