Case Report: Long-term maternal and neonatal outcomes after nivolumab therapy in metastatic tonsillar sarcomatoid squamous cell carcinoma.

Background: Immunotherapy with checkpoint inhibitor (ICI) has revolutionized the treatment of cancer including squamous cell carcinoma. Nevertheless, there is an unmet need to gain a better understanding of the effect of these therapies on pregnancy and fertility. Treatment with anti-PD-1 therapy decreases fetal-maternal tolerance and increases the risk of pregnancy loss in animal studies. However, few data are currently available in humans. Case presentation: We report the case of conception and pregnancy, with successful maternal and fetal outcomes, in a young woman with metastatic squamous cell carcinoma originated from the palatin tonsil. She was 17-year-old at the diagnosis. After surgical removal of the primary tumor, she received adjuvant radiotherapy. Four years later she underwent surgery for a lung relapse and adjuvant chemotherapy. Three years later the patient experienced a pulmonary and mediastinal relapse. Immunotherapy with nivolumab was promptly started with a slow reduction of the disease until a near radiological complete response with a unique residual lung subpleural nodulation. Surgical romoval confirmed the residual disease of squamous cell carcinoma. Patient re-started immunotherapy with nivolumab but after 2 months, she was found to be 4 weeks pregnant. Treatment was stopped and, since the patient expressed her desire to carry her pregnancy to term, she was referred to gynecological and psychological support. She had an uneventful pregnancy, followed by spontaneous vaginal delivery. The baby was healthy and exhibited normal development. Furthermore, the patient breastfed until the sixth month without any adverse effects on the child growth. In November 2025, after 32 months of disease-free survival, the patient developed a new lung recurrence, presenting as a single 4-cm diameter lesion in the right lower lobe. In January 2026, she underwent surgical resection of the lesion and histology was consistent with the diagnosis of metastatic disease. Currently, in the absence of detectable disease, the patient continues active follow-up. Conclusions: Our case provides evidence that pregnancy and normal fetal development may occur after early exposure to nivolumab, Nevertheless, the impact of treatment interruption and pregnancy on disease recurrence remains an unresolved question.