Erythema multiforme‐like lesions in primary cutaneous aggressive cytotoxic epidermotropic CD8+ T‐cell lymphoma: A diagnostic and therapeutic challenge

Primary cutaneous aggressive cytotoxic epidermotropic CD8+ T‐cell lymphoma is an extremely rare, rapidly progressing, cutaneous lymphoma, with frequent systemic involvement and poor prognosis, that still represents a diagnostic and therapeutic challenge, especially in the early stage. Herein, we report a case of an elderly woman with a fulminant course, who at onset presented with clinical and pathological features mimicking erythema multiforme (EM) and treated with cyclosporine that led to rapid deterioration with fatal outcome 6 months after disease onset. Histopathology showed a lichenoid, epidermotropic and nodular, angiocentric, dermal and subcutaneous infiltrate of sF1, CD8+, CD45RA+ small to medium‐sized atypical lymphoid cells, which strongly expressed cytotoxic markers. Monoclonal T‐cell‐γ receptor was clonally rearranged and array‐CGH showed numerous chromosomal imbalances. This case evidences the clinical, pathological and therapeutic challenges involved in this tumor. The first biopsy showed an interface dermatitis‐like pattern, revealing the deceptive features that early cutaneous infiltrates of this aggressive lymphoma may have. A high suspicion for aggressive CTCL and a low threshold for repeat biopsies should be maintained when faced with rapidly progressing and/or ulcerative EM‐like lesions, especially if immunomodulatory therapy is being considered.