A veterinary physical exam has revealed splenic enlargement in a cat. What is the likely diagnosis?

The presence of splenic enlargement in a cat can be associated with several potential conditions, but the most likely diagnosis in this scenario is lymphoma. Lymphoma is a common hematopoietic tumor in cats that often presents with splenic involvement, leading to splenomegaly. This condition can arise from the proliferation of lymphocytes within the spleen, causing noticeable enlargement, and can often be seen in younger cats, although it can occur in older cats as well.

When considering other conditions such as hemangiosarcoma, mast cell tumor, and splenic torsion, while these may also cause splenomegaly, they may not be as directly tied to the typical presentation seen in cases of lymphoma. Hemangiosarcoma is highly aggressive and often associated with other clinical signs, such as an acute abdomen, due to rupture of the tumor. Mast cell tumors are more often localized skin tumors, although they can sometimes have systemic effects but would typically not present primarily as splenic enlargement. Splenic torsion, while it also causes splenomegaly, is usually characterized by acute onset of severe clinical signs such as pain, vomiting, or shock, which are not mentioned in this question.

Thus, lymphoma aligns most closely