The Atypical Presentation of Diffuse Large B-cell Lymphoma in a Lower Limb Soft Tissue Mass: A Case Report.

We report a case of an 80-year-old male with a progressively enlarging, painful mass in the left lower limb, initially misdiagnosed as cellulitis. The patient did not respond to antibiotic therapy, prompting further investigation. Imaging revealed two large soft tissue masses, and biopsy confirmed diffuse large B-cell lymphoma (DLBCL) of germinal center origin. Despite treatment with R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone) chemotherapy and palliative radiotherapy, the disease progressed, and the patient died approximately one year after diagnosis. This report illustrates the diagnostic challenge posed by extranodal DLBCL when it mimics common soft tissue infections. Delayed diagnosis in our case was caused by the benign clinical presentation and limited access to imaging in the primary care setting. Clinicians should maintain a high index of suspicion for malignancy in atypical or unresponsive soft tissue lesions. Early referral, multidisciplinary evaluation, and appropriate imaging are critical to improving outcomes in such rare presentations.