Secondary Acute Myeloid Leukemia in Treatment-Naïve Primary Testicular Diffuse Large B-Cell Lymphoma.

Secondary acute myeloid leukemia (sAML) typically arises from a prior myeloid malignancy or as a complication of cytotoxic therapy for other cancers. Rarely, it may develop without antecedent treatment, particularly in lymphoid malignancies. We report an unusual case of sAML in a treatment-naïve patient previously diagnosed with primary testicular diffuse large B-cell lymphoma (DLBCL). A 58-year-old male initially presented with Stage 1E primary testicular DLBCL and declined recommended treatment. Five years later, he developed symptoms and laboratory features of acute myeloid leukemia (AML), confirmed as monocytic subtype (M5) via immunophenotyping. Despite planned hypomethylating agent-based therapy, he succumbed during bridging treatment. This case highlights the diagnostic importance of immunophenotyping and an uncommon clinical trajectory from untreated lymphoid malignancy to sAML.