Pulmonary Dissemination in Adult-Onset Recurrent Respiratory Papillomatosis: A Rare and Severe Manifestation

Recurrent respiratory papillomatosis (RRP) commonly affects the upper airways, and lung parenchymal involvement is extremely rare. We present a case of adult-onset laryngotracheal RRP with lung parenchymal involvement that progressed despite systemic bevacizumab and ultimately required a left lower lobectomy. Histological features were characteristic of a squamous papilloma. Unusually, parenchymal involvement was present, with solid intra-alveolar nests cradled by preserved alveolar septa. Cytologic atypia and keratinisation were present; however, the absence of stromal desmoplasia and invasion precluded a diagnosis of squamous cell carcinoma and made overall classification challenging in this case. This case highlights the complexity of managing RRP with pulmonary involvement, particularly when disease progression persists despite systemic therapy such as systemic bevacizumab.