Faecal Occult Blood Test

Case of the Month (Emma Scurrell September 2012)

Conjunctival melanoma in a dog

A 7-year-old male neutered Border Terrier has undergone enulceation of his right eye for a melanoma involving the dorsal palpebral conjunctiva.



Fig 1. Enucleated specimen with attached eyelids. A poorly delineated pigmented tumour is present in the dorsal conjunctiva (blue arrow).


Fig 2.  Sparsely pigmented neoplastic melanocytes. The blue arrows highlight the mitotic figures (H&E, x400).
 

Fig 3.  Neoplastic melanocytes often proliferate and form nests within the epithelium (of either the skin or mucosal surface) at the epidermal-dermal or mucosal-stromal junction and this is known as junctional activity. This junctional activity often extends beyond the main clinically visible tumour and can make complete excision difficult. Neoplastic nonpigmented melanocytes form intraepithelial nests in this section of bulbar conjunctiva. (H&E, x 200) 







Final Diagnosis

Malignant conjunctival melanoma 


Discussion


The majority of conjunctival melanomas in the dog are histopathologically malignant and therefore carry a risk of post-surgical recurrence and metastasis. This is in contrast to melanocytic tumours arising in the skin (including the eyelid), the majority of which are benign in the dog. Following excision of conjunctival melanomas, additional tumours may also sometimes arise in the near vicinity of the surgical site which are presumably satellite lesions arising via lymphatic spread. Conjunctival melanomas in dogs most commonly affect the third eyelid but the palpebral and bulbar conjunctiva can also be involved such as in this case. 

Previous Monthly Cases

Hypertensive Retinopathy January 2010
FIP in a cat - uncommon presentation February 2010
Phaeohyphomycosis    March 2010 
Scleral Rupture April 2010
Canine and feline epulides May 2010
Erythema multiforme in a labrador retreiver June 2010
Keloidal fibrosarcoma in a labrador retreiver July 2010
Cutaneous epitheliotropic lymphoma  August 2010 
Benign cutaneous histiocytoma  September 2010 
Iridociliary adenoma October 2010
Proliferative thrombovascular necrosis of the pinnae November 2010
Signet-ring cell carcinoma in the stomach of a dog December 2010
Cutaneous infiltrative lipoma in a labrador January 2011

Tonsillar squamous cell carcinoma February 2011
Canine orbital meningioma March 2011
"Lung-digit" syndrome in a cat April 2011
Hepatic amyloidosis in a cat May 2011
Haemophagocytic histiocytic sarcoma June 2011
Alternaria spp. infection in an immunocompromised dog July 2011
Ocular manifestation of lymphoma in a cat  August 2011
Kerion dermatophytosis in a Cocker spaniel September 2011
Subcuticular coenurus in a rabbit  October 2011
Optic nerve glioma in a dog November 2011
Malignant transformation of a viral papilloma in a dog  December 2011
Uveodermatological syndrome in an Akita
January 2012
Cutaneous angiostomatosis in a dog  February 2012
Transitional cell carcinoma in a dog  March 2012
Corneal inclusion cysts in a dog   April 2012
Extraskeletal osteosarcoma in a dog  May 2012
Subungual melanoma in a dog  June 2012
Retrobulbar grass seed in a dog   July 2012
Lungworm infection associated with hypercalcaemia in a dog  August 2012



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Faecal Occult Blood Test