Detection of TRAF1‐ALK fusion in skin lesions of systemic ALK+ anaplastic large cell lymphoma initially involving the skin and the draining lymph node

Abstract A case of cytoplasmic anaplastic lymphoma kinase (ALK)‐positive anaplastic large cell lymphoma (ALCL) initially involving the skin in a 44‐year‐old Japanese female is reported. The patient had a hemorrhagic erythematous tumor on the right thigh without any systemic symptoms. Pathology showed diffuse infiltration of CD30‐positive anaplastic large cells positive for epithelial membrane antigen and cytoplasmic ALK. The right inguinal lymph node showed infiltration of tumor cells in the marginal sinus. Only 2 weeks after radiation therapy, the patient developed multiple subcutaneous nodules and lung involvement. Even after subsequent multichemotherapy sessions, cutaneous recurrence occurred. Literature review of cytoplasmic ALK‐positive ALCL initially involving in the skin revealed that skin lesions were mostly seen in the extremities and that half of the cases developed extracutaneous lesions. Radiation and chemotherapy were effective for most cases. Inverse RT‐PCR identified a tumor necrosis factor receptor‐associated factor (TRAF)1 ‐ ALK fusion in our case. Most reported cases with this translocation experienced repeated changes in chemotherapy, suggesting poorer prognosis. Although ALK‐positive ALCL generally responds well to chemotherapy, the presence of a TRAF1 ‐ ALK fusion may suggest resistance to treatment. Detection of fusion partners of ALK is important for predicting clinical courses and deciding treatment options.