Lymphoma is caused by malignant clonal expansion of lymphoid cells and most commonly arises from lymphoid tissues including the [[Bone Marrow|bone marrow]], [[Thymus|thymus]], [[Lymph Nodes - Anatomy & Physiology|lymph nodes]] and [[Spleen - Anatomy & Physiology|spleen]]. Lymphoma is documented to be the most common haematopoietic [[Neoplasia - Pathology|neoplasm]] in dogs. | Lymphoma is caused by malignant clonal expansion of lymphoid cells and most commonly arises from lymphoid tissues including the [[Bone Marrow|bone marrow]], [[Thymus|thymus]], [[Lymph Nodes - Anatomy & Physiology|lymph nodes]] and [[Spleen - Anatomy & Physiology|spleen]]. Lymphoma is documented to be the most common haematopoietic [[Neoplasia - Pathology|neoplasm]] in dogs. |