Conclusion

Aggressive B‐cell lymphoma may be difficult to diagnose as initial symptoms can be confused with infections or neurologic or thrombotic events. The underlying malignancy was preceded by fever, AMS, and unexplained superficial bilateral upper‐extremity thrombosis. When patients have persistent systemic symptoms and a negative workup for infectious, autoimmune, and neurologic etiologies, clinicians should have a high index of suspicion for hematologic malignancy. The knowledge of this possibility in advance will help in early diagnosis and management.