Changes

Melanocytes are '''neuroectodermal cells''' and proliferations may arise from the '''epidermis, the dermis or the adnexa'''.

Melanocytes are '''neuroectodermal cells''' and proliferations may arise from the '''epidermis, the dermis or the adnexa'''.

The link between UV-light radiation and the development of melocytic tumours, which is seen in humans, has not been seen in domestic animals.

The link between UV-light radiation and the development of melanocytic tumours, which is seen in humans, has not been seen in domestic animals.

These tumours are most common in '''dogs, gray horses and miniature pigs'''. They are uncommon in goats and cattle and rare in cats and sheep.  

These tumours are most common in '''dogs, gray horses and miniature pigs'''. They are uncommon in goats and cattle and rare in cats and sheep.  

==Melanomas in dogs==

==Melanomas in Dogs==

Melanocytomas are more frequent than malignant melanomas.  

Melanocytomas are more frequent than malignant melanomas.  

===Clinical signs===

===Clinical Signs===

Melanocytomas are frequently found on the '''head and forelimbs''' of middle-aged and older dogs. There may be a predilection for males.

Melanocytomas are frequently found on the '''head and forelimbs''' of middle-aged and older dogs. There may be a predilection for males.

Treatment of melanocytomas involves '''complete excision'''. The tumours are benign and this is curative.

Treatment of melanocytomas involves '''complete excision'''. The tumours are benign and this is curative.

Malignant melanomas are '''aggressive and have considerable metastatic potential'''.

Malignant melanomas are '''aggressive and have considerable metastatic potential'''. '''Complete excision''' is generally indicated, however this may be difficult if the tumour is very infiltrated into the tissue. Digit tumours require '''amputation''' and oral tumours may be treated by '''hemimandibulectomy'''.

 

'''Complete excision''' is generally indicated, however this may be difficult if the tumour is very infiltrated into the tissue.  

 

Digit tumours require '''amputation''' and oral tumours may be treated by '''hemimandibulectomy'''.

Radiotherapy and chemotherapy have not been shown to be effective.

Radiotherapy and chemotherapy have not been shown to be effective.

Prognosis is generally '''poor''', with an overall survival time of less than a year.

Prognosis is generally '''poor''', with an overall survival time of less than a year.

==Melanomas in horses==

==Melanomas in Horses==

They are mostly found in '''gray horses''', especially in Lipizzaners, Arabs and Percherons.

They are mostly found in '''gray horses''', especially in Lipizzaners, Arabs and Percherons.

Most are '''benign''' but some invasive variants with metastatic potential exist.

Most are '''benign''' but some invasive variants with metastatic potential exist.

===Clinical signs===

===Clinical Signs===

Predilection sites include: the '''perineum and the base of the tail''', but they can also occur in other areas including the '''parotid gland'''.  

Predilection sites include: the '''perineum and the base of the tail''', but they can also occur in other areas including the '''parotid gland'''.  

'''Intra-lesional chemotherapy''' with cisplatin or carboplatin has been used after surgical debulking if the mass cannot be entirely removed.

'''Intra-lesional chemotherapy''' with cisplatin or carboplatin has been used after surgical debulking if the mass cannot be entirely removed.

==Melanomas in pigs==

==Melanomas in Pigs==

Melanocytic neoplasms of pigs are seen as '''congenital lesions and sporadically in adults''' of the Sinclair (Hormel) miniature pigs and Duroc and Duroc crosses.

Melanocytic neoplasms of pigs are seen as '''congenital lesions and sporadically in adults''' of the Sinclair (Hormel) miniature pigs and Duroc and Duroc crosses.

===Clinical signs===

===Clinical Signs===

These tumours can be found anywhere on the body. Generally multiple, they can appear as pigmented macules or patches with smooth borders, ulcerated pigmented lesions, or as deeper, slightly raised, blue masses. Deeply invasive melanomas are often associated with metastatic disease.  

These tumours can be found anywhere on the body. Generally multiple, they can appear as pigmented macules or patches with smooth borders, ulcerated pigmented lesions, or as deeper, slightly raised, blue masses. Deeply invasive melanomas are often associated with metastatic disease.  

The lymph nodes and lungs are the most common sites of metastasis.  

The lymph nodes and lungs are the most common sites of metastasis.  

===Treatment and prevention===

===Treatment and Prevention===

Not all of these tumors become invasive, and many undergo '''spontaneous regression''' associated with an intense lymphocytic infiltrate.  

Not all of these tumors become invasive, and many undergo '''spontaneous regression''' associated with an intense lymphocytic infiltrate.  

[[Category:To Do - Review]]

 

[[Category:Expert Review]]

[[Category:Oropharynx_-_Pathology]]

[[Category:Oropharynx_-_Pathology]]

[[Category:Liver, Secondary Tumours]]

[[Category:Liver, Secondary Tumours]]

 

[[Category:Neoplasia]]

[[Category:Neoplasia]]