Abstract
Diffuse large B-cell lymphoma (DLBCL) can arise in both lymph nodes and extranodal sites. DLBCLs rarely present in the soft tissue of the upper extremity. We report a case of a 64-year-old woman who presented with a large left upper arm mass and underwent surgical resection under the presumptive diagnosis of sarcoma but the final pathology showed DLBCL. Sarcomas are common malignant tumors of the soft tissue of the extremities, but lymphomas also occasionally present as a soft tissue mass. It is important to keep lymphomas in mind in order to avoid unnecessary surgical excisions.