Medical records from five institutions from January 2000 through December 2015 were reviewed and dogs with cytologically- or histologically-confirmed malignant anal sac melanoma were identified.
Signalment, clinical signs, staging, cytology, histopathologic analysis, surgical and non-surgical treatments were extracted from the medical records.
The referring veterinarians and owners were contacted for follow-up data.
Eleven dogs were included and survival data was available for all.
The most common clinical signs were bloody anal sac discharge and perianal licking.
Initial treatments pursued included surgery (n=8), chemotherapy (n=1), and palliative treatment with pain medications and stool softeners (n=2).
In an adjuvant setting, melanoma vaccine was pursued following surgery in three dogs and chemotherapy in one dog.
Regardless of treatment, progression-free survival (mean 92 · 5 days) and overall survival times (median 107 days) were short.
Dogs in this case series had a guarded to poor prognosis regardless of treatment.
Ten of 11 dogs were euthanased due to local or distant disease progression.
Only 1 of 11 dogs was alive one year after diagnosis.
An understanding of tumour behaviour in this location could lead to improved survival times with earlier diagnosis and treatment.
Source: Vinayak, A., Frank, C. B., Gardiner, D. W., Thieman-Mankin, K. M. and Worley , D. R. (2017), Malignant anal sac melanoma in dogs: eleven cases (2000 to 2015). Journal of Small Animal Practice, 58: 231–237. doi: 10.1111/jsap.12637
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