Adult nasal chondromesenchymal hamartoma: a rare and benign tumour with aggressive malignant transformation.

Nasal chondromesenchymal hamartoma (NCMH) is an extremely rare benign tumour of the nasal cavity predominantly described in infants. We report a case involving a 48-year-old woman who had been diagnosed with NCMH a year earlier and now re-presented with a short history of progressive nasal blockage, recurrent epistaxis and orbital apex syndrome. Histopathology was suggestive of malignant transformation into sinonasal sarcoma. However, following multidisciplinary team (MDT) discussions, including second and third opinions from external departments, the histological diagnosis was revised to 'NCMH with bizarre stromal cells'. Despite this, the lesion demonstrated malignant features of rapid, invasive growth and was treated with palliative radiotherapy. The patient later developed radiological evidence of lung and liver metastases with subsequent pulmonary emboli. Shortly after this, she passed away. This case is unique in its diagnostic challenge, with ambiguous histopathological findings, and highlights the importance of an MDT approach when managing complex sinonasal tumours.