A 45-year-old woman presents to the

hospital complaining of difficulty in breathing when lying flat, chest

tightness, dizziness and fainting. Imaging identifies a pedunculated mass

within the left atrium, which is attached to the interatrial septum. Histopathological

evaluation describes characteristic “lepidic” cells within an abundant

mucopolysaccharide matrix. Further investigations reveal an association of the

tumour with the Carney complex.

Which neoplasm is most likely present?