Primary Cutaneous Anaplastic Large Cell Lymphoma Mimicking Pyoderma Gangrenosum: An Atypical Presentation and Diagnostic Challenge.

Primary cutaneous anaplastic large cell lymphoma (PC-ALCL) is a rare subtype of cutaneous T-cell lymphoma that is known for its CD30-positive atypical large lymphoid cells. PC-ALCL usually presents as solitary nodules and has both clinical and histological features that could mimic other cutaneous lymphomas, which can lead to misdiagnosis. We report the case of a 62-year-old patient presenting with chronic ulcers whose condition at first mimicked pyoderma gangrenosum (PG), but eventually turned out to be PC-ALCL following immunohistochemical investigations. Radiological assessment demonstrated suspected regional lymph node involvement. The patient responded partially to cyclophosphamide, doxorubicin, vincristine, etoposide, and prednisone (CHOEP) chemotherapy and achieved a complete metabolic response after second-line chemotherapy consisting of dexamethasone, high-dose cytarabine, and carboplatin (DHAC) followed by BEAM-ASCT consolidation. This case highlights diagnostic and therapeutic challenges in atypical presentations of PC-ALCL.