Primary Cutaneous Diffuse Large B-cell Lymphoma Presenting as a Non-healing Axillary Ulcer.

Primary cutaneous diffuse large B-cell lymphoma (PCDLBCL) is a rare, aggressive lymphoma primarily affecting the skin. We report an unusual case of a female patient in her late 50s with a persistent non-healing ulcer in the left axilla, initially misdiagnosed as cutaneous tuberculosis. Despite empirical treatment, the ulcer worsened, leading to further investigation and a revised diagnosis of germinal centre-type PCDLBCL through biopsy and immunohistochemistry. The patient showed significant improvement in the wound following chemotherapy, but succumbed to complications of severe neutropenia and acute respiratory distress syndrome (ARDS). This case underscores the importance of early biopsy and histopathological evaluation in atypical, rapidly progressing cutaneous lesions to avoid misdiagnosis and ensure timely treatment, ultimately significantly improving patient outcomes in cases of primary cutaneous diffuse large B-cell lymphoma if managed and diagnosed early.