Pulmonary mixed squamous and glandular papilloma: diagnostic challenges of a rare lesion when the clock is ticking. How to avoid interpretation mistakes

Pulmonary mixed squamous and glandular papillomas (MSCGPs) are rare, benign neoplasms with peculiar clinical and histological features. However, on occasion, they can present certain characteristics that overlap with other neoplasms including carcinomas. Recognising these features is hence important for treatment purposes. Molecular studies can sometimes help in further characterisation, although they should not guide the diagnosis which ultimately relies on morphology. We report a challenging case of MSCGP with unusual features, received during intraoperative consultation. We highlight the subtle morphological features to help avoid overcalling a benign lesion as malignant.