The Aggressive Lymphomas and Leukemias

This chapter explores aggressive lymphomas and leukemias in veterinary medicine, focusing on their diverse presentations, classifications, and diagnostic challenges. Lymphomas, originating from lymphocytes, manifest in various tissues and are classified based on anatomic location, histologic morphology, immunophenotype, and genetic aberrations. The World Health Organization (WHO) classification lists numerous distinct lymphoid neoplasms in humans and veterinary medicine, with evidence-based classification being crucial for treatment, disease monitoring, and research. However, extensive diagnostics may be impractical or cost-prohibitive, potentially delaying treatment. The chapter aims to guide veterinary practitioners on minimal diagnostic requirements before treatment decisions. Clinical manifestations of canine lymphoma vary by type and location, with multicentric lymphoma characterized by generalized lymphadenopathy and systemic signs. Other forms include gastrointestinal, colorectal, and mediastinal lymphomas, each presenting unique symptoms. The chapter emphasizes the importance of accurate diagnosis while balancing practical constraints to ensure optimal patient care. The clinical presentation of extranodal lymphoma in dogs varies by affected organ, with cutaneous forms manifesting as nodules, plaques, or ulcers, and epitheliotropic T-cell lymphoma progressing through distinct stages. Mucocutaneous involvement may appear as erythematous, hypopigmented lesions, while extranodal sites include lymph nodes, spleen, liver, and bone marrow.