Lymphoma is widely recognized in veterinary medicine. However, studies focused on secondary lymphoma after chemotherapy do not exist in veterinary medicine. An 11-year-old, spayed female Shih-Tzu dog was diagnosed with mammary gland carcinoma. Twenty-five months after carboplatin treatment, the dog developed generalized lymphadenopathy (GL), diagnosed as high-grade T-cell lymphoma by immunohistochemistry. Another spayed female Shih-Tzu dog who was 15-year-old had biopsy-induced gastrointestinal stromal tumour. Three months after being treated with Toceranib, the dog developed GL that was diagnosed by PCR for antigen receptor rearrangement as T-cell lymphoma. An eight-year-old, castrated male Mongrel dog was diagnosed with mast cell tumour. The dog was treated with vinblastine, but 14 months later, GL was revealed. Fine-needle aspiration indicated lymphoma. The owner declined to investigate the cell lineage. All three dogs developed GL after chemotherapy. We suggest that secondary lymphoma can develop in dogs after chemotherapy for a primary cancer, and thus long-term follow-up is necessary.
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