Immune checkpoint inhibitors are known to induce 'immune pneumonitis' in 3-6% of patients treated for lung cancer. However, their dramatic efficacy in as much as 20% of patients led to recent registrations in squamous, and then non-squamous lung carcinoma, in second line setting after failure of first-line chemotherapy, while large phase 3 trials are on-going, to assess first-line immunotherapy, either alone or in combination with chemotherapy. Pulmonary Sarcomatoid carcinomas consist of a rare subset of highly aggressive and poorly differentiated non-small-cell lung carcinomas (NSCLC), with poor prognosis and chemo-resistance. Although exhibiting high expression of programmed death ligand-1 (PD-L1), their sensitivity to inhibitors of PD-1/PD-L1 axis is still unknown. Here we report a case of lung sarcomatoid carcinoma with Nivolumab dramatic and long-lasting efficacy, but occurrence of a very specific pattern of lung toxicity, the so-called 'organizing bronchiolitis syndrome'. As more and more NSCLC patients are promised to receive PD-1 inhibitors as part of their treatment, we feel that specific features of such Nivolumab-induced organizing pneumonitis should be known. Although corticosteroid sensitivity is high, recurrence is frequent because of premature steroid tapering, as for all other causes of organizing pneumonias, and probably because of the Nivolumab long tissue half-life.
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