A seven-year-old male neutered Irish setter was treated for a metastatic anal sac adenocarcinoma (ASAC) andhypercalcaemia by complete surgical excision of the primary tumour and partial excision of the sublumbar lymph nodes.Further enlargement of the sublumbar lymph nodes was linked to recurrent hypercalcaemia 3 months after surgicaltreatment. Medical treatment with Toceranib and Clodronate showed modest results in the treatment of the tumourand the hypercalcaemia. Radiotherapy of the sublumbar lymph nodes and later concurrent carboplatin chemotherapyresulted in partial tumour remission with marked reduction in size of the lymph nodes and normalization of thecalcaemia. Unfortunately, concurrently with subsequent relapse of the hypercalaemia, the dog developed hypertrophicosteopathy (HO) and lumbar spinal metastasis and the dog was euthanized. To the authors’ knowledge, this is thesecond case of metastatic apocrine gland carcinoma of the anal sac associated with HO and the first case that describethe development of HO late in the stage of the disease.