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==Introduction==
[[Image:dogpap1.gif|right|thumb|100px|<small><center>Oral Papilloma Neoplasia in Dog (Courtesy of Alun Williams (RVC))</center></small>]]
[[Image:dogpap1.gif|right|thumb|100px|<small><center>Oral Papilloma Neoplasia in Dog (Courtesy of Alun Williams (RVC))</center></small>]]
An adenoma is a '''benign epithelial tumour''' arising in the epithelium of the '''mucosa''' (stomach and intestines), '''glands''' (endocrine and exocrine) and '''ducts'''.
Adenomas observed in veterinary species include:
[[Image:brunner gland adenoma.jpg|thumb|right|150px|Adenoma of brunners glands (duodenum) (Courtesy of Bristol BioMed Image Archive)]]
==Perianal Adenoma==
[[Image:normal perianal gland.jpg|thumb|right|200px|Perianal gland - normal (Courtesy of Bristol BioMed Image Archive)]]
[[Image:perianal gland adenoma histopath.jpg|thumb|200px|Perianal gland - adenoma (Courtesy of Bristol BioMed Image Archive)]]
[[Image:perianal gland adenoma.jpg|thumb|right|200px|Perianal adenoma - gross appearance (Courtesy of Bristol BioMed Image Archive)]]
These tumours, also called hepatoid gland tumours, arise from the solid, '''modified sebaceous circumanal glands'''. They are the third most common tumour in '''intact male dogs''', and arise more frequently in '''older dogs'''.
The tumour is '''under hormonal control'''. Hepatoid glands are also found at the tail head, prepuce and other skin sites, and tumours can also arise from there.
====Clinical features====
Adenomas occur alone or in number, as round, well-differentiated, freely-movable masses. Tumours can become ulcerated and secondarily infected. There can be signs of perianal pain and tenesmus.
==Tumours of the Perianal Area==
====Diagnosis====
'''Cytology''' of the mass will reveal large hepatoid cells with a round, central nuclei, multiple nucleoli, and an abundant cytoplasm. There may be concurrent inflammation or haemorrhage. Cytology cannot distinguish adenomas from [[Adenocarcinoma#Perianal gland adenocarcinoma|adenocarcinomas]], and further investigations should be carried out if malignancy is suspected.
===Hepatoid Gland Tumours (Perianal Adenomas)===
====Treatment====
'''Castration''' is the treatment of choice and 95% of tumours will regress. Administration of oestrogens or anti-androgens can also be considered, but side-effects of those hormones should not be forgotten. Surgical removal of the tumour may be necessary if it is large, or in females.
==Sweat Gland Adenoma==
This is a tumour of the '''apocrine sweat gland''' and is rare in dogs and cats. It can be difficult to differentiate from an adenocarcinoma, and '''immunohistochemistry''' has been used for this purpose.
Adenomas rarely ulcerate, are associated with '''little local inflammation''' and have a cystic feel on palpation.
They occur most commonly in '''older dogs and cats''', and are usually restricted to the head.
Wide surgical excision usually carries a good prognosis.
==Ceruminous Gland Adenoma==
This occurs with some frequency in dogs and cats, and is thought to be linked to the '''presence of long-standing [[Otitis Externa - Cat and Dog|otitis externa]]''', leading to increased glandular dysplasia.
These tumours usually occur in older animals, and conservative local resection is usually sufficient to manage them.
==Sebaceous Gland Adenoma==
These are common in older dogs and cats and are usually distinctly '''wart-like or cauliflower-like''' in appearance.
Histopathology shows large mature sebaceous lobules with increased numbers of basaloid epithelial cells and a low mitotic activity.
The prognosis is good with surgical resection.
==Salivary Gland Adenoma==
This tumour is rare in animals, and the malignant adenocarcinoma is much more common.
==Mammary Gland Adenoma==
This is a benign tumour which is quite common in cats and dogs.
Find out more information on [[Mammary Neoplasia|mammary tumours]].
==Intestinal Adenoma==
[[Image:brunner gland adenoma.jpg|thumb|right|200px|Adenoma of brunners glands (duodenum) (Courtesy of Bristol BioMed Image Archive)]]
Intestinal adenomas are found in both the [[Small Intestine Overview - Anatomy & Physiology|small]] and [[Large Intestine - Anatomy & Physiology|large intestines]]. Intestinal adenomas usually grow into the lumen and can be called '''adenomatous polyps'''.
Depending on the type of the insertion base, the adenoma may be '''pedunculated''' with a long stalk, or '''sessile''' with a broad base. This influences the method of resection and the rate of recurrence, as pedunculated tumours are much more easily removed.
==Hepatic Adenoma==
It is seen mostly in '''sheep and cattle''' and usually presents as a single, pale, soft, often large nodule, which is well demarcated from adjacent tissue, often with a noticeable capsule. The tissue has a '''normal hepatocytic appearance'''. No portal tracts can be seen within the mass and a capsule surrounds the growth.
==Cholangiocellular Adenoma==
Also called '''biliary adenoma''', it is very rare but has been reported in dogs and cats. It shows an expansive growth and consists of slightly dilated, occasionally cystic structures, lined with cuboidal or flattened, well differentiated biliary epithelium.
==Pancreatic Adenoma==
[http://w3.vet.cornell.edu/nst/nst.asp?Fun=Image&imgID=7754 Image of multifocal pancreatic adenoma in a dog from Cornell Veterinary Medicine]
[http://w3.vet.cornell.edu/nst/nst.asp?Fun=Image&imgID=7754 Image of multifocal pancreatic adenoma in a dog from Cornell Veterinary Medicine]
Adenoma of the '''exocrine (zymogen) cells of the pancreas''' is known in several species and is recognised by its ductal or acinar pattern of cells, with an expanding growth pattern and '''complete encapsulation'''. Cystic spaces may be created by the tumour cells, which may also project in a papillary pattern into the lumen of the cysts.
'''Hyperplastic nodules''' may be present in the pancreas of older animals. They are usually less well encapsulated than adenomas, but may be difficult to distinguish with certainty. They are usually multiple.
{{Learning
|Vetstream = [https://www.vetstream.com/canis/Content/Disease/dis01994.asp Adenoma and adenocarcinoma]<br>[https://www.vetstream.com/equis/search?s=adenoma Search: adenoma]
|flashcards = [[Cytology Q&A 07]]
}}
==References==
Withrow, S. (2001) '''Small animal clinical oncology''' ''Elsevier Health Sciences''
Morrison, W. (2002) '''Cancer in dogs and cats: medical and surgical management''' ''Teton NewMedia''
Carlyle Jones, T. (1997) '''Veterinary pathology''' ''Wiley-Blackwell''
Cheville, N. (1999) '''Introduction to veterinary pathology''' ''Wiley-Blackwell''
{{review}}
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[[Category:Expert Review]]
[[Category:Oropharynx - Pathology]]
[[Category:Oropharynx - Pathology]]
[[Category:Intestines - Proliferative Pathology]]
[[Category:Intestines - Proliferative Pathology]]
[[Category:Liver, Primary Tumours]]
[[Category:Liver, Primary Tumours]]
[[Category:Pancreas_-_Hyperplastic_and_Neoplastic_Pathology]]
[[Category:Pancreas_-_Hyperplastic_and_Neoplastic_Pathology]]
[[Category:Neoplasia]]
[[Category:Neoplasia]]