Clinical outcome and prognosis of dogs with histopathological features consistent with epitheliotropic lymphoma: a retrospective study of 148 cases (2003-2015).

Background: Limited information is available regarding the treatment and outcome of dogs with epitheliotropic lymphoma. The disease typically has a poor prognosis.

Objectives: To characterize the clinical signs, identify prognostic factors and evaluate the treatment outcome of dogs with epitheliotropic lymphoma.

Methods: A retrospective review of medical records from 2003 to 2015. Treatment details, tumour response and survival time were recorded for 148 dogs. Potential prognostic factors were evaluated for their statistical effect on median survival time.

Results: The overall median survival time for dogs was 264 days (cutaneous: 130 days; mucocutaneous/mucosal: 491 days). On multivariate analysis, a shorter median survival time was associated with the cutaneous form (P < 0.001) and the presence of multiple lesions (P < 0.001). Among 80 dogs with cutaneous lesions, chemotherapy treatment (P < 0.001) and having a solitary lesion (P < 0.001) were associated with longer median survival. In 72 dogs with multiple cutaneous lesions, chemotherapy intervention (P < 0.001), retinoid treatment (P = 0.001) and complete remission (P = 0.001) were associated with longer median survival. In 68 dogs with mucocutaneous/mucosal lesions, decreasing age (P = 0.020) and a solitary lesion (P = 0.015) were associated with longer median survival.

Conclusion: Canine epitheliotropic lymphoma may be divided into cutaneous and mucocutaneous/mucosal forms. Solitary lesions have a better prognosis. Dogs with multiple lesions appear to benefit from chemotherapy and retinoid treatment, with those attaining complete remission having longer survival times. Multi-agent chemotherapy could be considered in dogs with cutaneous lesions that fail to respond to single-agent chemotherapy.