Rapidly Evolving Extensive Fluorodeoxyglucose-Positive Soft-Tissue Activity During Nivolumab Therapy

A 41-year-old woman with stage IIa melanoma of the upper thigh presented with diffuse erythematous induration of the upper thigh expanding to the lower left abdominal area and palpable subcutaneous nodules on the ipsilateral gluteal region and leg during nivolumab therapy. What is your diagnosis?

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