Introduction

Superficial vein thrombosis (SVT) is less investigated than deep vein thrombosis (DVT) and occurs mainly in the lower extremities. Unusual, bilateral superficial thromboses of the upper extremities represent approximately 15% of upper limb cases [1, 2]. Studies have demonstrated active cancer in 7 to 17% of patients with SVT and thus screening for occult malignancies is important in the absence of obvious local triggers such as intravenous therapy or trauma [3, 4, 5]. Venous thromboembolism (VTE) is also a recognized complication in 5%–10% of patients with lymphoma [6].

Altered mental status (AMS) in older patients not only raises the possibility of paraneoplastic conditions in the differential diagnosis but may also result from more common infectious, metabolic, or neurological etiologies [7, 8]. On the other hand, the aggressive non‐Hodgkin lymphomas known as high‐grade B‐cell lymphomas (HGBCLs), which include diffuse large B‐cell lymphoma (DLBCL) and related conditions [9, 10], can cause a wide spectrum of systemic symptoms due to cytokine dysregulation, hypercoagulability, and, on uncommon occasions, metabolic or paraneoplastic neurological complications [11, 12]. Malignant lymphomas are among the most common neoplastic causes of fever of unknown origin (FUO) [13], and misdiagnosis is common [14].