Faecal Occult Blood Test

Case of the Month (Emma Scurrell July 2013)

Intraosseous epidermoid cyst in the toe of a dog

The fourth digit of the left foreleg was amputated in a 3-year-old, female Labrador Retriever in which radiographs indicated a focal expansile lytic lesion affecting the third phalanx (P3).  







  Fig 1. Radiograph of the left foot reveals a discrete cystic mass within P3 of the fourth digit.





Radiograph courtesy of Gilmore Vets Ltd of Durham.


Fig 2. The bone of P3 is focally replaced by a discrete cyst. The cyst contains abundant keratin and is lined by a layer of well-differentiated, benign squamous epithelium (arrows).
 

 







Final Diagnosis

Intraosseous epidermoid cyst of the third phalanx

Discussion

Intraosseous epidermoid cysts are not common but account for lytic lesions occuring most commonly in the distal phalanges of dogs. Other sites occasionally affected include the vertebrae and skull. The cause of these benign cysts is not known but the main thoughts include nests of heterotopic ectoderm sequestered within bone during embryonic development or a penetrating wound resulting in traumatic implantation of epidermis into the underlying bone.

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
Conjunctival melanoma in a dog  September 2012
Pneumocystis infection in a Cavalier King Charles Spaniel  October 2012
Fungal keratitis and secondary endophthalmitis in a horse November 2012
Myeloid leukaemia with lymph node invasion in a dog    December 2012
Cutaneous toxoplasmosis in a cat   January 2013
Glomerulonephritis in a dog  February 2013
Splenic mast cell tumour in a cat  March 2013
Laryngeal rhabdomyoma in a dog  April 2013
Mycobacterial infection in an eye May 2013
Key Gaskell syndrome in a cat June 2013



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Faecal Occult Blood Test